Agenda packet, regular meeting — Laguna Hills City Council, February 10, 2026 (part 7 of 11)

FILE: MC-SYSB.WSW W S P G W - CIVILDESIGN Version 14.06 PAGE 2 Program Package Serial Number: 1881
WATER SURFACE PROFILE LISTING Date:10- 9-2025 Time: 9:35:35

MILL CREEK DEVELOPMENT

SYSTEM B OUTLET HYDRAULICS
BY KAM 100925
************************************************************************************************************************** ******** | Invert | Depth | Water | Q | Vel Vel | Energy | Super |Critical|Flow Top|Height/|Base Wt| |No Wth Station | Elev | (FT) | Elev | (CFS) | (FPS) Head | Grd.El.| Elev | Depth | Width |Dia.-FT|or I.D.| ZL |Prs/Pip -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|
L/Elem |Ch Slope | | | | SF Ave| HF |SE Dpth|Froude N|Norm Dp | "N" | X-Fall| ZR |Type Ch *********|*********|********|*********|*********|*******|*******|*********|*******|********|********|*******|*******|***** |******* | | | | | | | | | | | | |
107.978 272.978 .116 273.093 4.30 14.87 3.43 276.53 1.27 .45 2.50 .330 2.500 .00 0 .0 -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- |-
.723 .0198 .4871 .35 1.39 7.70 .31 .015 .00 .00 RECTANG | | | | | | | | | | | | |
108.701 272.992 .110 273.102 4.30 15.59 3.78 276.88 1.40 .45 2.50 .330 2.500 .00 0 .0 -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- |-
.679 .0198 .5680 .39 1.51 8.28 .31 .015 .00 .00 RECTANG | | | | | | | | | | | | |
109.381 273.005 .105 273.111 4.30 16.36 4.15 277.26 1.54 .45 2.50 .330 2.500 .00 0 .0 -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- |-
.639 .0198 .6625 .42 1.64 8.89 .31 .015 .00 .00 RECTANG | | | | | | | | | | | | |
110.020 273.018 .100 273.118 4.30 17.15 4.57 277.69 1.69 .45 2.50 .330 2.500 .00 0 .0 -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- |-
.600 .0198 .7729 .46 1.79 9.55 .31 .015 .00 .00 RECTANG | | | | | | | | | | | | |
110.620 273.030 .096 273.126 4.30 17.99 5.03 278.15 .00 .45 2.50 .330 2.500 .00 0 .0 -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- |-
TRANS STR .0189 .7842 2.49 .10 10.25 .015 .00 .00 RECTANG | | | | | | | | | | | | |
113.800 273.090 .272 273.362 4.30 24.82 9.56 282.92 .00 .87 .89 1.000 .000 .00 1 .0 -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- |-

3.937 .1832 .3435 1.35 .27 9.91 .32 .010 .00 .00 PIPE
| | | | | | | | | | | | |
117.737 273.811 .266 274.077 4.30 25.67 10.24 284.31 .00 .87 .88 1.000 .000 .00 1 .0 -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- |-

5.013 .1832 .3857 1.93 .27 10.39 .32 .010 .00 .00 PIPE
| | | | | | | | | | | | |
122.750 274.730 .257 274.987 4.30 26.93 11.26 286.25 .00 .87 .87 1.000 .000 .00 1 .0 -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- |-
.344 .5004 .4104 .14 .26 11.10 .24 .010 .00 .00 PIPE
| | | | | | | | | | | | |
123.094 274.902 .257 275.159 4.30 26.88 11.22 286.38 .00 .87 .87 1.000 .000 .00 1 .0 -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- |-

8.663 .5004 .3837 3.32 .26 11.07 .24 .010 .00 .00 PIPE

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FILE: MC-SYSB.WSW W S P G W - CIVILDESIGN Version 14.06 PAGE 3 Program Package Serial Number: 1881
WATER SURFACE PROFILE LISTING Date:10- 9-2025 Time: 9:35:35

MILL CREEK DEVELOPMENT

5.573 .5004 .3357 1.87 .27 10.37 .24 .010 .00 .00 PIPE
| | | | | | | | | | | | |
137.330 282.026 .275 282.302 4.30 24.44 9.27 291.57 .00 .87 .89 1.000 .000 .00 1 .0 -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- |-

4.032 .5004 .2937 1.18 .28 9.70 .24 .010 .00 .00 PIPE
| | | | | | | | | | | | |
141.363 284.044 .285 284.329 4.30 23.30 8.43 292.76 .00 .87 .90 1.000 .000 .00 1 .0 -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- |-

3.109 .5004 .2571 .80 .29 9.08 .24 .010 .00 .00 PIPE
| | | | | | | | | | | | |
144.471 285.600 .295 285.895 4.30 22.22 7.66 293.56 .00 .87 .91 1.000 .000 .00 1 .0 -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- |-

2.493 .5004 .2250 .56 .29 8.50 .24 .010 .00 .00 PIPE
| | | | | | | | | | | | |
146.964 286.847 .305 287.152 4.30 21.18 6.97 294.12 .00 .87 .92 1.000 .000 .00 1 .0 -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- |-

2.052 .5004 .1970 .40 .31 7.95 .24 .010 .00 .00 PIPE
| | | | | | | | | | | | |
149.016 287.874 .316 288.190 4.30 20.20 6.33 294.52 .00 .87 .93 1.000 .000 .00 1 .0 -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- |-

1.722 .5004 .1726 .30 .32 7.44 .24 .010 .00 .00 PIPE
| | | | | | | | | | | | |
150.738 288.736 .327 289.063 4.30 19.26 5.76 294.82 .00 .87 .94 1.000 .000 .00 1 .0 -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- |-

1.465 .5004 .1512 .22 .33 6.96 .24 .010 .00 .00 PIPE
| | | | | | | | | | | | |
152.204 289.469 .339 289.808 4.30 18.36 5.23 295.04 .00 .87 .95 1.000 .000 .00 1 .0 -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- |-

1.261 .5004 .1325 .17 .34 6.50 .24 .010 .00 .00 PIPE
| | | | | | | | | | | | |
153.465 290.100 .351 290.451 4.30 17.51 4.76 295.21 .00 .87 .95 1.000 .000 .00 1 .0 -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- |-

1.093 .5004 .1161 .13 .35 6.08 .24 .010 .00 .00 PIPE

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FILE: MC-SYSB.WSW W S P G W - CIVILDESIGN Version 14.06 PAGE 4 Program Package Serial Number: 1881
WATER SURFACE PROFILE LISTING Date:10- 9-2025 Time: 9:35:35

MILL CREEK DEVELOPMENT

SYSTEM B OUTLET HYDRAULICS
BY KAM 100925
************************************************************************************************************************** ******** | Invert | Depth | Water | Q | Vel Vel | Energy | Super |Critical|Flow Top|Height/|Base Wt| |No Wth Station | Elev | (FT) | Elev | (CFS) | (FPS) Head | Grd.El.| Elev | Depth | Width |Dia.-FT|or I.D.| ZL |Prs/Pip -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|
L/Elem |Ch Slope | | | | SF Ave| HF |SE Dpth|Froude N|Norm Dp | "N" | X-Fall| ZR |Type Ch *********|*********|********|*********|*********|*******|*******|*********|*******|********|********|*******|*******|***** |******* | | | | | | | | | | | | |
154.557 290.647 .363 291.010 4.30 16.69 4.33 295.34 .00 .87 .96 1.000 .000 .00 1 .0 -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- |-
.954 .5004 .1018 .10 .36 5.68 .24 .010 .00 .00 PIPE
| | | | | | | | | | | | |
155.511 291.124 .376 291.500 4.30 15.91 3.93 295.43 .00 .87 .97 1.000 .000 .00 1 .0 -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- |-
.837 .5004 .0893 .07 .38 5.31 .24 .010 .00 .00 PIPE
| | | | | | | | | | | | |
156.348 291.543 .390 291.933 4.30 15.17 3.58 295.51 .00 .87 .98 1.000 .000 .00 1 .0 -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- |-
.736 .5004 .0783 .06 .39 4.96 .24 .010 .00 .00 PIPE
| | | | | | | | | | | | |
157.084 291.911 .404 292.315 4.30 14.47 3.25 295.57 .00 .87 .98 1.000 .000 .00 1 .0 -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- |-
.650 .5004 .0688 .04 .40 4.63 .24 .010 .00 .00 PIPE
| | | | | | | | | | | | |
157.735 292.237 .419 292.656 4.30 13.79 2.95 295.61 .00 .87 .99 1.000 .000 .00 1 .0 -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- |-
.575 .5004 .0604 .03 .42 4.32 .24 .010 .00 .00 PIPE
| | | | | | | | | | | | |
158.310 292.525 .434 292.959 4.30 13.15 2.69 295.64 .00 .87 .99 1.000 .000 .00 1 .0 -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- |-
.510 .5004 .0531 .03 .43 4.04 .24 .010 .00 .00 PIPE
| | | | | | | | | | | | |
158.820 292.780 .450 293.230 4.30 12.54 2.44 295.67 .00 .87 1.00 1.000 .000 .00 1 .0 -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- |-
.620 .2982 .0474 .03 .45 3.76 .28 .010 .00 .00 PIPE
| | | | | | | | | | | | |
159.440 292.965 .462 293.427 4.30 12.11 2.28 295.70 .00 .87 1.00 1.000 .000 .00 1 .0 -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- |-
.741 .2982 .0424 .03 .46 3.57 .28 .010 .00 .00 PIPE
| | | | | | | | | | | | |
160.180 293.186 .480 293.665 4.30 11.54 2.07 295.73 .00 .87 1.00 1.000 .000 .00 1 .0 -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- |-
.651 .2982 .0373 .02 .48 3.33 .28 .010 .00 .00 PIPE

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FILE: MC-SYSB.WSW W S P G W - CIVILDESIGN Version 14.06 PAGE 5 Program Package Serial Number: 1881
WATER SURFACE PROFILE LISTING Date:10- 9-2025 Time: 9:35:35

MILL CREEK DEVELOPMENT

SYSTEM B OUTLET HYDRAULICS
BY KAM 100925
************************************************************************************************************************** ******** | Invert | Depth | Water | Q | Vel Vel | Energy | Super |Critical|Flow Top|Height/|Base Wt| |No Wth Station | Elev | (FT) | Elev | (CFS) | (FPS) Head | Grd.El.| Elev | Depth | Width |Dia.-FT|or I.D.| ZL |Prs/Pip -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|
L/Elem |Ch Slope | | | | SF Ave| HF |SE Dpth|Froude N|Norm Dp | "N" | X-Fall| ZR |Type Ch *********|*********|********|*********|*********|*******|*******|*********|*******|********|********|*******|*******|***** |******* | | | | | | | | | | | | |
160.831 293.380 .498 293.878 4.30 11.00 1.88 295.76 .00 .87 1.00 1.000 .000 .00 1 .0 -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- |-
.572 .2982 .0329 .02 .50 3.10 .28 .010 .00 .00 PIPE
| | | | | | | | | | | | |
161.404 293.550 .517 294.068 4.30 10.49 1.71 295.78 .00 .87 1.00 1.000 .000 .00 1 .0 -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- |-
.503 .2982 .0290 .01 .52 2.89 .28 .010 .00 .00 PIPE
| | | | | | | | | | | | |
161.907 293.700 .537 294.238 4.30 10.00 1.55 295.79 .00 .87 1.00 1.000 .000 .00 1 .0 -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- |-
.441 .2982 .0255 .01 .54 2.69 .28 .010 .00 .00 PIPE
| | | | | | | | | | | | |
162.347 293.832 .558 294.390 4.30 9.54 1.41 295.80 .00 .87 .99 1.000 .000 .00 1 .0 -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- |-
.385 .2982 .0226 .01 .56 2.50 .28 .010 .00 .00 PIPE
| | | | | | | | | | | | |
162.733 293.947 .580 294.527 4.30 9.09 1.28 295.81 .00 .87 .99 1.000 .000 .00 1 .0 -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- |-
.335 .2982 .0199 .01 .58 2.32 .28 .010 .00 .00 PIPE
| | | | | | | | | | | | |
163.068 294.047 .604 294.651 4.30 8.67 1.17 295.82 .00 .87 .98 1.000 .000 .00 1 .0 -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- |-
.290 .2982 .0177 .01 .60 2.15 .28 .010 .00 .00 PIPE
| | | | | | | | | | | | |
163.358 294.133 .629 294.762 4.30 8.27 1.06 295.82 .00 .87 .97 1.000 .000 .00 1 .0 -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- |-
.248 .2982 .0157 .00 .63 1.99 .28 .010 .00 .00 PIPE
| | | | | | | | | | | | |
163.606 294.207 .655 294.862 4.30 7.88 .96 295.83 .00 .87 .95 1.000 .000 .00 1 .0 -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- |-
.209 .2982 .0139 .00 .66 1.83 .28 .010 .00 .00 PIPE
| | | | | | | | | | | | |
163.814 294.269 .684 294.953 4.30 7.52 .88 295.83 .00 .87 .93 1.000 .000 .00 1 .0 -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- -|- |-
.173 .2982 .0124 .00 .68 1.69 .28 .010 .00 .00 PIPE

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FILE: MC-SYSB.WSW W S P G W - CIVILDESIGN Version 14.06 PAGE 6 Program Package Serial Number: 1881
WATER SURFACE PROFILE LISTING Date:10- 9-2025 Time: 9:35:35

MILL CREEK DEVELOPMENT

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9272 Jeronimo Road, Suite 104,  Irvine  CA 92618  (949) 297-3856

PRELIMINARY GEOTECHNICAL INVESTIGATION,

PROPOSED RESIDENTIAL DEVELOPMENT,
23161 MILL CREEK DRIVE,

LAGUNA HILLS, CALIFORNIA
Dated: August 15, 2024
Project No. 244006-01
Prepared For:

Toll Brothers
350 Commerce, Suite 200
Irvine, California 92602

Page 1058 of 1727 ends

9272 Jeronimo Road, Suite 104 • Irvine • CA 92618 • (949) 297-3856 August 15, 2024 Project No. 244006-01
Ms. Aylene Chu
Toll Brothers
350 Commerce, Suite 200
Irvine, California 92602
Subject: Preliminary Geotechnical Investigation, Proposed Residential Development, 23161 Mill Creek Drive, Laguna Hills, California
In accordance with your request, LGC Valley, Inc. (LGC) has performed a preliminary geotechnical investigation for the proposed multi-family residential development located at 23161 Mill Creek Drive (Assessor Parcel Number [APN] 588-142-07) in the City of Laguna Hills, California. The purpose of our geotechnical investigation was to evaluate the existing on-site geotechnical conditions relative to the proposed multi-family residential development of the site and to provide geotechnical recommendations applicable to the grading operations and future site construction for the project.

Our geotechnical study included: 1) review of the available geotechnical as-graded documents of the site and adjacent properties, and pertinent geotechnical and geologic reports and maps relative to the general vicinity; 2) a site reconnaissance, geologic mapping, and field exploration consisting of the excavation of six small-diameter borings; 3) laboratory testing of representative on-site soil samples; 4) geotechnical analysis of the collected data; and 5) preparation of this report that includes our findings, conclusions, opinions, and recommendations relative to the grading and development of the site.

Based on the results of our preliminary geotechnical investigation, it is our professional opinion that the proposed site development is feasible from a geotechnical standpoint provided the recommendations included in this report are incorporated into the project plans and specifications and followed during site grading and construction. If you have any questions regarding our report, please contact this office. We appreciate this opportunity to be of service.

Respectfully submitted,
LGC VALLEY, INC.

Randall K. Wagner, CEG 1612 Basil Hattar, GE 2734
Senior Project Geologist Principal Engineer
Distribution: (1) Addressee (via e-mail)

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Project No. 233016-01 Page i August 15, 2024

TABLE OF CONTENTS
Section
Page

1.0 INTRODUCTION..............................................................................................................1

1.1 Purpose and Scope of Services .................................................................................1

1.2 Site and Project Description......................................................................................3

1.3 Proposed Development.............................................................................................3

1.4 Subsurface Investigation and Laboratory Testing......................................................4

1.5 Existing As-Graded Geotechnical Conditions..........................................................4

2.0 GEOTECHNICAL CONDITIONS...................................................................................5

2.1 Site Geology.............................................................................................................5

2.1.1 Artificial Older Fill (Afo)..............................................................................5

2.1.2 Tertiary-Aged Sespe Formation (Ts).............................................................5

2.2 Geologic Structure....................................................................................................6

2.3 Landslides.................................................................................................................6

2.4 Groundwater.............................................................................................................6

2.5 Surface Water and Flooding ....................................................................................6

2.6 Faulting ....................................................................................................................7

2.7 Seismicity and Related Effects ................................................................................7

2.7.1 Seismic Design Criteria ...............................................................................8

2.7.2 Lurching and Shallow Ground Rupture......................................................9

2.7.3 Liquefaction and Dynamic Settlement .........................................................9

2.7.4 Tsunamis and Seiches..................................................................................9

2.8 Slope Stability........................................................................................................10

2.9 Expansion Potential ................................................................................................10

2.10 Soluble Sulfate and Corrosivity of the On-Site Soils ..............................................10

2.11 Excavation Characteristics......................................................................................10

2.12 Earthwork Shrinkage and Bulking ..........................................................................11

2.13 Stormwater Infiltration/Percolation.........................................................................11

3.0 CONCLUSIONS...............................................................................................................13

4.0 RECOMMENDATIONS .................................................................................................16

4.1 Site Earthwork........................................................................................................16

4.1.1 Site Preparation..........................................................................................16

4.1.2 Removal and Recompaction........................................................................16

4.1.3 Cut/Fill Transition Condition ....................................................................17

4.1.4 Shrinkage/Bulking ......................................................................................17

4.1.5 Temporary Excavation Stability ................................................................17

4.1.6 Temporary Shoring ....................................................................................18

4.1.7 Fill Placement and Compaction .................................................................20

4.1.8 Trench Backfill and Compaction ................................................................20

4.2 Foundation Design..................................................................................................20

4.2.1 General Foundation Selection ....................................................................20

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Project No. 233016-01 Page ii August 15, 2024

4.2.2 Bearing Capacity........................................................................................21

4.2.3 Post-Tension Foundation............................................................................21

4.2.4 Mat Foundations........................................................................................23

4.2.5 Foundation Settlement................................................................................24

4.2.6 Building Clearance and Foundation Setbacks ..........................................24

4.3 Lateral Earth Pressures for Retaining Walls..........................................................25

4.4 Segmental Retaining Wall Recommendations.......................................................26

4.5 Soldier Pile Wall Recommendations.....................................................................29

4.6 Preliminary Pavement Recommendations.............................................................30

4.6.1 Asphalt Concrete (AC) Pavement ...............................................................30

4.6.2 Portland Cement Concrete Pavement.........................................................31

4.6.3 Vehicular Concrete Paver Pavement ..........................................................31

4.7 Nonstructural Concrete Flatwork...........................................................................31

4.8 Corrosivity to Concrete and Metal ..........................................................................32

4.9 Freestanding Walls.................................................................................................33

4.10 Control of Surface Water and Drainage Control .....................................................33

4.11 Construction Observation and Testing....................................................................33

5.0 LIMITATIONS..................................................................................................................35

LIST OF TABLES, APPENDICES, AND ILLUSTRATIONS
Tables
Table 1 - California Building Code Seismic Design Parameters (page 8) Table 2 - Earthwork Shrinkage and Bulking Estimates (page 11) Table 3 - Preliminary Geotechnical Parameters for Post-Tension Foundation Design (page 23) Table 4 - Lateral Earth Pressures for Retaining Walls (page 25) Table 5 - Design Soil Strength Parameters for Segmental Retaining Walls (page 27) Table 6 - Preliminary AC Pavement Design Sections (page 30) Table 7 - Nonstructural Concrete Flatwork (page 32)
Figures
Figure 1 - Site Location Map (page 2)
Figure 2 - Geotechnical Map (rear of text)
Figure 3 - Retaining Wall Drainage Detail (rear of text) Appendices
Appendix A - References
Appendix B - Geotechnical Boring Logs (Current Study)
Appendix C - Laboratory Testing Procedures and Test Results (Current Study) Appendix D - Previous Geotechnical Borings Logs (by Others) Appendix E - General Earthwork and Grading Specifications for Rough Grading

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Project No. 244006-01 Page 1 August 15, 2024

1.0 INTRODUCTION

1.1 Purpose and Scope of Services
The purpose of this preliminary geotechnical investigation was to identify and evaluate the existing geologic and geotechnical conditions at the subject site (Figure 1) and to provide preliminary geotechnical design criteria relative to the proposed multi-family development of the site. Recommendations for site grading, construction, preliminary foundation design for the proposed structures, and other relevant aspects of the proposed development are included herein to address the identified site geotechnical conditions.

Our scope-of-services for preparation of this document included:
 Review of available reports including prior geotechnical investigations, as-graded geotechnical documents, and other geotechnical related documents of the site and adjacent properties; and pertinent published geologic, geotechnical, and seismic reports and maps relative to the general vicinity (Appendix A).  A site reconnaissance and geologic mapping of the site.  A subsurface investigation consisting of the excavation, sampling, and logging of six smalldiameter hollow-stem borings. The locations of the borings are shown on the Geotechnical Map (Figure 2). The logs of the borings are presented in Appendix B. The test borings were sampled and logged under the supervision of a licensed engineering geologist from our firm. The excavations were performed to evaluate the general characteristics of the subsurface conditions of the site including the classification of site soils and the determination of the depth to competent soil.
 Laboratory testing of representative soil samples obtained during our investigation (Appendix C).
 Review of boring logs from the geotechnical studies previously performed on the site and/or adjacent sites. The applicable boring logs are presented in Appendix D.  Determination of seismic design parameters based on current building code requirements. • Geotechnical analyses and evaluation of the data obtained during this study.  Preparation of this report presenting our findings, conclusions, opinions, and recommendations including the General Earthwork and Grading Specifications for Rough Grading (Appendix E) with respect to the evaluated geotechnical conditions at the site and the proposed development.

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Site Location
Basemap: ESRI World Imagery Basemap, Accessed August 13, 2024 Figure 1
Site Location Map
23161 Mill Creek Drive
Laguna Hills, California
244006-01
Toll/23161 Mill Creek

BIH/RKW
Not-to-Scale
August 15, 2024
Project Name
Project No.

Eng. / Geol.

Scale
Date

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Project No. 244006-01 Page 3 August 15, 2024

1.2 Site and Project Description
The approximately 2.44-acre site is located on the west side of Mill Creek Drive southwest of the intersection of Mill Creek Drive and Lake Forest Drive in the northwestern portion of the City of Laguna Hills, California (Figure 1). The site is bounded by Mill Creek Drive on the east, existing business developments on the north (23091 Mill Creek Drive) and south (23201 Mill Creek Drive), and a residential development on the west. The site currently consists of one three-story commercial building in the northern portion of the site and a large, paved parking lot in the central and southern portions of the site. Additional improvements include underground utility lines, retaining walls along the south and west sides of the parking lot, landscaping, and associated improvements. A north- to east-facing slope up to approximately 40 to 45 feet in height is present on the north and east sides of the property that descends to the parking lot of 23091 Mill Creek Drive on the north and Mill Creek Drive on the east. An approximately 10 to 15-foot-tall north-facing slope is present along the south side of the property.

Review of available aerial photographs, historical Google Earth images, old topography maps, and geotechnical reports of adjacent properties (Appendix A) indicate that the site (and general vicinity) was rough graded in the late 1970’s/early 1980’s and the site was precise graded in 1985/1986. The as-graded geotechnical reports and grading plans specific to 23161 Mill Creek were not available at the City of Laguna Hills; and consequently, were not reviewed by us for the purposes of this study.

Prior to the grading of the site, the property was located along the north side of a northwestsoutheast trending ridgeline. Mill Creek Drive along the east side of the property was the location of a small tributary canyon that was partially in-filled during the grading of the area.

Based on Google Earth images, elevations of the relatively flat portion of the property range from approximately 297 to 301 feet along the north side of the property to 300 to 316 feet along the south side. Based on the original topography, current site grades, and our limited subsurface investigation, we anticipate that the prior grading of the site consisted of a cut-fill condition with shallow fills located across the site (existing parking lot area) and deeper fills along the northern side of the property (and beneath the existing building) with backfill soils behind the on-site retaining walls.

1.3 Proposed Development
We understand that the proposed development will consist of a multi-family townhome residential development consisting of nine 3- to 6-unit structures (totaling 43 units).

Preliminary plans show perimeter retaining walls are being considered around the perimeter of the site consisting of a combination of block walls, pile walls, and segmental (MSE) walls ranging in height from 4 to 17 feet. Anticipated associated improvements will include asphalt concrete (AC) streets and parking areas, a gated entrance, Portland cement concrete (PCC) sidewalks, open‐space areas/landscaping, underground utility lines, a storm water biofiltration system, and associated improvements.

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1.4 Subsurface Investigation and Laboratory Testing
Our subsurface investigation was performed on May 8, 2024, and consisted of the excavation, sampling, and logging of six small diameter hollow-stem borings (designated Borings LGC-B-1 through LGC-B-6) excavated to depths ranging from approximately 10.5 to 20.5 feet. All of the borings were extended into competent formational material. The logs of the borings are presented in Appendix B while the approximate locations of the borings are shown on the Geotechnical Map (Figure 1). At least three days prior to the start of our subsurface investigation, the proposed boring excavation locations were staked, Underground Service Alert (USA) notified, and the applicable information provided to them. The USA Dig Alert Number for this project is A241230333.

During the subsurface investigation, representative bulk samples and relatively undisturbed samples were collected for laboratory testing, and were forwarded to EGLAB, Inc. (EGL) and to LGC Valley, Inc. for classification testing. Laboratory testing was performed on representative soil samples and included moisture/density, Atterberg Limit, sieve analysis, consolidation, expansion index, direct shear, remolded direct shear, maximum density, sulfate content, chloride content, pH, and minimum resistivity testing. A summary of the test procedures and printouts of the laboratory test results are presented in Appendix C. The moisture and density test results were presented on the boring logs included in Appendix B.

1.5 Existing As-Graded Geotechnical Conditions
Based on our review of available PDF copies of public records obtained from the City of Laguna Hills (see References - Appendix A); a number of different preliminary geotechnical investigations and as-grade reports have been prepared for adjacent properties. However, the preliminary geotechnical investigations and as-grade reports for the subject property (23161 Mill Creek Drive) and the property to the south (23201 Mill Creek Drive) were not available for our review. The findings and conclusions of the available geotechnical reports relative to 23091 Mill Creek Drive (located to the north of the subject site) are discussed below.

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2.0 GEOTECHNICAL CONDITIONS

2.1 Site Geology
Based on our subsurface exploration and review of the available previous geotechnical reports for the property and pertinent geologic literature and maps (Appendix A), the bedrock unit at the site is the Tertiary-aged Sespe Formation. The bedrock is overlain by older artificial fills placed during previous development of the site. The approximate extent of the mapped geologic units present on the site is depicted on the Geotechnical Map (Figure 2). A brief description of the geologic units encountered on the site is presented below.

2.1.1 Artificial Older Fill (Afo)
Based on our review of the available geotechnical reports of the site and the general vicinity, it is our understanding that the on-site existing artificial fills (up to approximately 25+ feet in thickness) were placed and documented by Irvine Soils Engineering, Inc. (1980) and G.A. Nicoll and Associates, Inc. (1986); however, these reports were not available for our review.

Existing artificial fills were encountered in our recent geotechnical borings within the existing parking areas across the site and were found to consist of silty to clayey sands that were slightly moist and medium dense. The depths of the encountered fills ranged from approximately 1 to 5 feet in thickness. Based on the available data, the deeper existing fills are located underlying the existing structure and slope located along the northern portion of the site. Due to the existing site improvements and access issues, this deeper fill was not investigated as a part of this study.

Based on our understanding of the placement/documentation of the existing older fills and our observations and testing of the encountered fills on-site, it is our preliminary conclusion that the existing fills are considered suitable for support of the proposed structures, provided remedial removals are performed of any fills disturbed during site demolition. For confirmation purposes, an additional evaluation of the fill soils (after the existing building is demolished and removed) should be performed. This additional evaluation will need to include surface excavation (drilling), sampling, and laboratory testing to determine the competency of the existing fill soils, and suitability for support of the proposed structures. Additional remedial removal or foundation recommendations will be provided at that time, as necessary.

2.1.2 Tertiary-Aged Sespe Formation (Ts)
Based on our review of geologic maps of the site and general vicinity, the site is underlain by massive to thickly bedded non-marine gray to red pebbly sandstones and silty to clayey sandstones with interbedded siltstones and claystones of the Tertiaryaged Sespe Formation (Morton, Hauser, and Ruppert, 1999; and Morton and Miller,

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2006). The results of our subsurface investigation indicated that the Sespe Formation soils encountered consisted of fine to coarse sandstone, silty and clayey fine to medium sandstone, and sandy to clayey siltstone with little to no pebbles.

2.2 Geologic Structure
Based on our review of geotechnical documents relative to the property directly north of the site, it appears that a large-diameter boring was excavated in the northern portion of the 23161 Mill Creek Drive property in 1986 by G. A. Nicoll and Associates Inc. (Lawmaster & Co, Inc., 1989). The location of the boring (Boring N-B-2) and the bedding attitudes obtained in the boring are shown on Figure 2. This information was obtained from a geotechnical investigation map of 23091 Mill Creek Drive (Lawmaster, 1989). As indicated, the bedding observed in the Sespe Formation ranges from N68W to N65E dipping 5 to 33 degrees to the south. As a result, bedding is dipping into-the-slope and is considered favorable in regard to slope stability. It should be noted that the geotechnical investigation report by G.A. Nicoll and Associates in 1986 that includes the boring log and the description of the subsurface investigation was not available for our review.

2.3 Landslides
Based on our review of aerial photographs and available geotechnical reports for the site, (Appendix A), no evidence of landsliding or other slope instability conditions were observed on-site or noted in the literature. Consequently, the potential for the existence of landslides is considered insignificant.

2.4 Groundwater
Review of available groundwater related internet web sites (Appendix A) indicates that groundwater is likely greater than 50 feet below the ground surface at the site. Groundwater is relatively shallow (generally less than 20 feet below the ground surface) in the large alluvial valley north and northeast of the site. As a result, groundwater is not expected to have a significant impact to the proposed development (provided the recommendations of this report are implemented during the design, grading, and construction of the proposed site improvements).

2.5 Surface Water and Flooding
Based on our review of the existing site grading plans and topography map of the site, sheet flow across the site is to the southeast. Surface water runoff relative to project design is the purview of the project civil engineer and should be directed away from planned structures. Due to the elevation of the site relative to drainages, flooding at the site is considered insignificant.

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2.6 Faulting
The southern California region has long been recognized as being seismically active. The seismic activity results from several active faults that cross the region, all of which are related to the San Andreas transform system, a broad zone of right lateral faults that extend from Baja California to Cape Mendocino. The numerous faults in Southern California include Holocene active, pre-Holocene active, and age-undetermined faults. The definitions of fault activity terms used here are based on those developed for the Alquist-Priolo Special Studies Zone/Earthquake Zone Act of 1972 (CGS, 2018).

Holocene active faults are those faults that have had surface displacement within Holocene time (approximately the last 11,700 years) and have been included within an Alquist-Priolo Earthquake Zone. Pre-Holocene faults have not moved in the last 11,700 years but may be considered potentially active. Age-undetermined faults are faults where the recency of fault movement has not been determined and may likely be considered inactive faults.

The site is not within the currently established Alquist-Priolo Earthquake Fault Zone for fault rupture hazard (formerly Special Studies Zones for fault rupture hazard). Based on a review of geologic literature, no active faults are known to occur beneath or in the general vicinity of the project site. Accordingly, it appears that there is little probability of surface rupture due to faulting beneath the site. There are, however, several faults located in sufficiently close proximity that movement associated with them could cause significant ground motion at the site.

Regional active faults that occur within the Laguna Hills and southern California area include the Newport-Inglewood fault zone to the west and the San Joaquin Hills blind thrust fault, Whittier-Elsinore, San Jacinto, and San Andreas faults to the east. The closest known active faults to the site are the San Joaquin blind thrust Hills fault located approximately 1 mile (1.7 kilometers) to the northeast, the Newport-Inglewood fault zone located approximately 7 miles (11.5 kilometers) to the southwest, and the Elsinore fault zone located approximately 16.5 miles (26.5 kilometers) to the northeast.

The main seismic parameters to be considered when discussing the potential for earthquakeinduced damage are the distances to the causative faults, earthquake magnitudes, and expected ground accelerations. Secondary effects of seismic shaking resulting from large earthquakes on the major faults in the southern California region include soil liquefaction and dynamic settlement. Other secondary seismic effects include shallow ground rupture, seiches and tsunamis. In general, these secondary effects of seismic shaking are a possibility throughout the Southern California region and are dependent on the distance between the site and the causative fault and the on-site geology.

2.7 Seismicity and Related Effects
We have performed site-specific analysis based on these seismic parameters for the site and the on-site geologic conditions. The results of our analysis are discussed in terms of the potential seismic events that could be produced by the maximum probable earthquakes. A

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maximum probable earthquake is the maximum earthquake likely to occur given the known tectonic framework.

2.7.1 Seismic Design Criteria
Based on the 2022 California Building Code (CBC) the site seismic characteristics for the project were evaluated per the guidelines set forth in Chapter 16, Section 1613 of the 2022 CBC. Representative site coordinates for the project site of Latitude

33.625942º N and Longitude -117.735614º W were utilized in our analyses. The maximum considered earthquake (MCE) spectral response accelerations (SMS and SM1) and adjusted design spectral response acceleration parameters (SDS and SD1) for Site Class C are provided in the following table.

Table 1
California Building Code Seismic Design Parameters
Selected Parameters from 2022 CBC, Section 1613 -
Earthquake Loads
Seismic Design
Values
Site Class (per Chapter 20 of ASCE 7) C
Risk-Targeted Spectral Acceleration for Short Periods (SS) 1.223g Risk-Targeted Spectral Accelerations for 1-Second Periods (S1) 0.439g Site Coefficient Fa [per CBC Table 1613.2.3(1)] 1.2
Site Coefficient Fv [per CBC Table 1613.2.3(2)] 1.5
Site Modified Spectral Acceleration for Short Periods (SMS) [Note: SMS = FaSS]

1.467g
Site Modified Spectral Acceleration for 1-Second Periods (SM1) [Note: SM1 = FvS1]

0.659g
Design Spectral Acceleration for Short Periods (SDS)
[Note: SDS = (2/3)SMS]

0.978g
Design Spectral Acceleration for 1-Second Periods (SD1) [Note: SD1 = (2/3)SM1]

0.439g
Seismic Design Category (per CBC Section 1613.2.5) D
Section 1803.5.12 of the 2022 CBC (per Section 11.8.3 of ASCE 7) states that the maximum considered earthquake ground motions, Peak Ground Acceleration (PGA) should be used for the geotechnical evaluations. The PGAM for the site is equal to

0.617g (USGS Seismic Design Maps based on ASCE/SEI 7-16 and ASCE/SEI 7-16 Table 1.5-2).

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A deaggregation of the PGA based on a 2,475-year average return period indicates that an earthquake magnitude of 6.89 at approximately 3.33 km (2.07 mi) from the site would contribute the most to this ground motion (USGS, 2014).

2.7.2 Lurching and Shallow Ground Rupture
Soil lurching refers to the rolling motion on the ground surface by the passage of seismic surface waves. Effects of this nature are not likely to be significant where the thickness of soft sediments do not vary appreciably under structures. Although there are several nearby active and potentially active faults, the native soils are dense, and no active faults are known or interpreted to cross the site. Based on this data, it is our opinion that the potential for lurching or shallow rupture at the site is very low to nil.

2.7.3 Liquefaction and Dynamic Settlement
Liquefaction is a seismic phenomenon in which loose, saturated, granular soils behave similarly to a fluid when subject to high-intensity ground shaking.

Liquefaction occurs when three general conditions exist: 1) shallow groundwater; 2) low density non-cohesive (granular) soils; and 3) high-intensity ground motion.

Liquefaction is typified by a buildup of pore-water pressure in the affected soil layer to a point where a total loss of shear strength occurs, causing the soil to behave as a liquid. Studies indicate that saturated, loose to medium dense, near surface cohesionless soils exhibit the highest liquefaction potential, while dry, dense, cohesionless soils and cohesive soils exhibit low to negligible liquefaction potential.

Effects of liquefaction on level ground include settlement, sand boils, and bearing capacity failures below structures.

Based on the anticipated relative density of the on-site soils and the depth to the static groundwater in the area of the proposed development; it is our opinion that the potential for liquefaction impacting the site is nil, and seismically induced settlements are considered to be negligible.

During a strong seismic event, seismically induced settlement can occur within loose to moderately dense, dry, or saturated granular soil. Settlement caused by ground shaking is often non-uniformly distributed, which can result in differential settlement.

Based on in-situ densities, and soil types, dry sand settlement and induced surface manifestations are not considered an issue at the site.

2.7.4 Tsunamis and Seiches
Due to the elevation of the proposed development at the site with respect to sea level and its distance from large open bodies of water, the potential of seiches and/or tsunami is considered to be very low.

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2.8 Slope Stability
Based on the massive to thickly bedded Sespe Formation on the site, favorable (into-theslope) geologic bedding conditions, and the construction of the proposed segmental geogrid retaining walls along the north and east sides of the property and the block and pile retaining walls along the west and south sides of the property, slope stability is not considered an issue with respect to site development. However, as part of our geotechnical review of the proposed segmental geogrid retaining walls and pile walls, a global slope stability analysis will be performed once the segmental wall designs are completed. The results will be presented in a future retaining wall plan review letter.

2.9 Expansion Potential
Expansion potential testing of representative on-site soil samples indicates that the on-site soils have a very low to low expansion potential (Appendix C). Although some of the near surface soils (Sespe Formation claystone layers) may have a medium to high expansion potential, we would anticipate the mixture and redistribution of site soils will result in a low expansion potential for the site. The as-graded soil conditions of the proposed building pads should be verified with confirmatory observation, sampling, and testing after site grading is completed and prior to the construction of the structures.

2.10 Soluble Sulfate and Corrosivity of the On-Site Soils Laboratory testing of representative on-site soils indicated the on-site soils tested had soluble sulfate contents that ranged from 0.005 to 0.007 percent (Appendix C). As a result, the on-site soils should be considered to have a negligible degree of corrosivity to concrete and have an Exposure Class of S0 in accordance with ACI 318R-14 Table 19.3.1.1. The as-graded sulfate content of the finish grade soils on the building pads should be verified upon completion of grading.

Minimum resistivity, pH, and chloride content tests were also performed on two representative soil samples obtained during our subsurface investigation. These corrosion tests resulted in a minimum resistivity of 1,300 to 1,700 ohm-centimeters, a pH of 7.82 to

8.15, and a chloride content of 125 to 140 ppm (Appendix C). Based on these results, the onsite soils should be considered moderately corrosive to buried metals in contact with the onsite soils.

2.11 Excavation Characteristics
The site is underlain by near surface soils consisting of silty fine to coarse sands, clayey to fine sandy silts, silty clay, siltstone/claystone, and sandstone layers. It is anticipated that the on-site materials can be excavated with conventional heavy-duty construction equipment and that difficult excavation and/or blasting is not anticipated. In addition, the anticipated site excavation and the proposed construction will not have an adverse impact on the adjacent properties.

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2.12 Earthwork Shrinkage and Bulking
The volume change of excavated on-site materials upon recompaction as fill is expected to vary with materials and location. Typically, the surficial soils and bedrock materials vary significantly in natural and compacted density, and therefore, accurate earthwork shrinkage/bulking estimate cannot be determined. However, the following factors (based on the results of our subsurface investigation and previous investigations of the site, laboratory testing, geotechnical analysis, and professional experience on nearby sites) are provided in Table 2 as guideline estimates. If possible, we suggest an area where site grades can be adjusted be provided as a balance area.

Table 2
Earthwork Shrinkage and Bulking Estimates
Geologic Unit Estimated
Shrinkage/Bulking
Artificial Fill and upper 1 to 2 feet of the site 3 to 7 percent shrinkage Sespe Formation 0 to 5 percent bulking

2.12 Stormwater Infiltration/Percolation
Based on our understanding of site development, on-site storm water will flow into proprietary underground biofiltration BMP structures that will treat the storm water and then discharge it into the on-site storm drain system that is connected to the storm drain system in Mill Creek Drive. We also understand that site infiltration is not currently proposed.

However, a future percolation/infiltration study may be required to determine the feasibility of storm water subsurface infiltration for the site.

Our limited subsurface investigation of the site that was performed on May 8, 2024 and consisted of the excavation, sampling, and logging of six small diameter hollow-stem borings excavated to depths ranging from approximately 10.5 to 20.5 feet, indicated the near surface soils consist of fill soils and Tertiary-Aged Sespe Formation. As encountered, the Sespe Formation soils consisted of fine to coarse sandstone, silty and clayey fine to medium sandstone, and sandy to clayey siltstone with little to no pebbles. Based on our professional experience with similar soils, infiltration of these sandy soils are likely feasible; however, the results will likely have a relatively low infiltration rate (slightly above the typical minimum required rate of 0.5 inches per hour). Infiltration into the fill soils and along the north, northeast, and east sides of the site are not recommended due to the presence of descending slopes, large retaining walls, and fill soils that will have a reduced factor-of-safety as the result of subsurface groundwater.

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Once the final storm water infiltration design is determined for the site, a percolation/infiltration study (in accordance with the City of Laguna Hills/County of Orange requirements) should be performed to determine the actual percolation/infiltration rate(s) at the proposed storm water infiltration locations and appropriate factor-of-safeties.

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3.0 CONCLUSIONS
Based on the results of our geotechnical investigation, evaluation, and review; it is our professional opinion that the proposed site development is feasible from a geotechnical standpoint, provided the recommendations included in this report are incorporated into the project plans and specifications, and followed during site grading and construction. Our geotechnical conclusions are as follows:
 Review of available aerial photographs, historical Google Earth images, old topography maps, and geotechnical reports of adjacent properties (Appendix A) indicate that the site (and general vicinity) was rough graded in the early 1980’s and the site was precise graded in 1986. The asgraded geotechnical reports and grading plans specific to 23161 Mill Creek were not available at the City of Laguna Hills; and consequently were not reviewed by us.  Based on our subsurface exploration and review of the available previous geotechnical reports for the property and pertinent geologic literature and maps, the bedrock unit at the site is the Tertiaryaged Sespe Formation that is overlain by artificial older fills. The fill soils are a mixture of silty to clayey sands, silty fine to coarse sands, clayey to fine sandy silts, and silty clay. The Sespe Formation generally consisted of massive to thickly bedded fine to coarse sandstone, silty and clayey fine to medium sandstone, and sandy to clayey siltstone with little to no pebbles. The fill soil layers encountered in our current geotechnical investigation were found to be competent and suitable for support of proposed structures, provided the recommendations of this report are followed during site grading and construction.
 After the removal of the existing buried underground utilities has been made, the trench locations should be surveyed, and the excavations should be replaced with fill soils compacted to a minimum 90 percent relative compaction (based on ASTM D1557). Where these trenches are located within the limits of the proposed multi-family building foundation footprints, special consideration should be made as the majority of the site is cut and the trenches will create cut/fill transition conditions.

Mitigation measures may include overexcavation of the upper 5 feet of the pad and replacement with compacted fill or backfilling the trenches with a 2-sack sand/cement slurry.  The existing on-site soils appear to be suitable material for use as fill provided, they are relatively free of rocks (larger than 8 inches in maximum dimension), organic material, and debris.
 The on-site formational material is anticipated to be massive to thickly bedded. The bedding observed in the Sespe Formation ranges from N68W to N65E dipping 5 to 33 degrees to the south (Lawmaster & Co, Inc., 1989). As a result, bedding is dipping into-the-slope and is considered favorable in regard to slope stability.
 There are no known landslides or other slope instability issues impacting the site.  Review of available groundwater related internet web sites (Appendix A) indicates that groundwater is likely greater than 50 feet below the ground surface at the site. Groundwater was not encountered during our recent subsurface investigation. Consequently, groundwater is not expected to have an impact on the proposed development.

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 Based on the topography of the site, surface water is anticipated to flow across the sheet-graded pad from the west to southeast.
 Due to the elevation of the site relative to existing drainages, flooding at the site is not considered an issue for the site.
 Active or potentially active faults are not known to exist on the site.  The site is not located within the Alquist-Priolo Earthquake Fault Zone (CGS, 2018). The closest known Holocene active faults to the site are the San Joaquin blind thrust Hills fault located approximately 1 mile (1.7 kilometers) to the northeast, the Newport-Inglewood fault zone located approximately 7 miles (11.5 kilometers) to the southwest, and the Elsinore fault zone located approximately 16.5 miles (26.5 kilometers) to the northeast.  The main seismic hazard that may affect the site is ground shaking from one of the active regional faults.
 Based on the relatively dense nature of the proposed compacted fill soils and existing formational material and lack of a permanent shallow groundwater condition, liquefaction and/or dynamic settlement at the site is considered very low to nil.
 Due to the elevation of the proposed development at the site with respect to sea level and its distance from large open bodies of water, the potential of seiches and/or tsunami is considered to be nil.
 Based on the massive to thickly bedded Sespe Formation on the site, generally favorable geologic bedding conditions, and the construction of the proposed segmental geogrid retaining walls along the north and west sides of the property, slope stability is not considered an issue with respect to site development. However, as part of our geotechnical review of the proposed geogrid retaining walls and pile walls, a global slope stability analysis will be performed once the wall designs are completed. The results will be presented in a future retaining wall plan review letter.
 Expansion potential testing of representative samples of the on-site soils indicate those soils have a very low to low expansion potential (Appendix C). Although some of the near surface soils may have a medium to high expansion potential, most of the soils on the site have a low expansion potential. The as-graded soil conditions of the proposed building pads should be verified with confirmatory observation, sampling, and testing after site grading is completed and prior to the construction of the structures.
 Laboratory testing of representative on-site soils indicated the on-site soils should be considered to have a negligible degree of corrosivity to concrete and have an Exposure Class of S0 in accordance with ACI 318R-14 Table 19.3.1.1.
 Minimum resistivity, pH, and chloride content tests were also performed on the two representative soil samples obtained during our subsurface investigation and these results indicate the on-site soils should be considered moderately corrosive to buried metals in contact with the on-site soils.

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 It is anticipated that the on-site materials can be excavated with conventional heavy-duty construction equipment and that difficult excavation and/or blasting is not anticipated.  The anticipated site excavation and the proposed construction will not have an adverse impact on the adjacent properties.
 The multi-family residential structures may be designed to be supported by post-tension or mat foundation systems.
 In order to reduce the potential for differential settlement in areas of cut/fill transitions, we recommend the upper 5 feet of the building pad be overexcavated and replaced with properly compacted fill to mitigate the transition condition beneath the proposed structure. This condition is likely along the north and west sides of the property, where existing buried utility lines that are abandoned and the trenches replace with compacted fill, and possibly in the eastern portion of the site along the property boundary.
 Based on our professional experience with similar soils, infiltration of the on-site sandy formational soils are likely feasible; however, a percolation/infiltration study (in accordance with the City of Laguna Hills/County of Orange requirements) should be performed to determine the actual percolation/infiltration rate(s) at the proposed storm water infiltration locations and appropriate factor-of-safeties.

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4.0 RECOMMENDATIONS

4.1 Site Earthwork
We anticipate that earthwork at the site will consist of site preparation and remedial grading and construction of site perimeter retaining walls followed by construction of the proposed slab-on-grade type foundations and associated improvements. We recommend that earthwork on-site be performed in accordance with the recommendations herein, the City of Laguna Hills grading requirements, and the General Earthwork and Grading Specifications for Rough Grading included in Appendix E. In case of conflict, the recommendations in the following sections shall supersede those included as part of Appendix E.

4.1.1 Site Preparation
Prior to grading of the area to receive structural fill or engineered structures, the ground surface should be cleared of obstructions, debris, potentially compressible material (such as undocumented fill soils, dry, disturbed, or desiccated documented fill and formational material and stripped of vegetation). Vegetation and debris should be removed and properly disposed of offsite. Holes resulting from the removal of buried obstructions or utilities, which extend below finished site grades, should be replaced with suitable compacted fill material. Areas to receive fill and/or other surface improvements should be scarified to a minimum depth of 6 inches, brought to a nearoptimum moisture condition, and recompacted to at least 90 percent relative compaction (based on American Standard of Testing and Materials [ASTM] Test Method D1557).

4.1.2 Removal and Recompaction
The upper portion of the site is underlain by potentially compressible/collapsible or unsuitable soils (i.e., desiccated existing fills, and formational material) which may settle under the addition of water, under the surcharge of fill, and/or foundation loads.

Compressible materials not removed by the planned grading should be excavated to competent material (as determined by the geotechnical consultant) and replaced with compacted fill soils. From a geotechnical perspective, soil that is removed may be placed as fill provided the material is relatively free from rocks (greater than 8-inches in maximum dimension), organic material and construction debris; is moistureconditioned or dried (as needed) to obtain above-optimum moisture content; and then recompacted prior to additional fill placement or construction.

All disturbed or desiccated fills underlying or within the influence of the proposed development should be removed to competent soils. The actual depth and extent of the required removals should be determined during grading operations by the geotechnical consultant; however, the estimated remedial removals are as follows:
we anticipate removals of up to 3 feet below existing grades; however, localized, deeper removals should be anticipated where deemed necessary by the geotechnical consultant based on observations during grading.

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4.1.3 Cut/Fill Transition Condition
In order to reduce the potential for differential settlement of proposed buildings located across cut/fill transitions, we recommend the entire cut portion of the transition building pads be overexcavated to a minimum depth of 5 feet and replaced with properly compacted fill to mitigate the transition condition beneath the proposed structure; or the building foundations deepened so that all foundation footings are founded on formational material. Where existing buried utility lines that will be abandoned are located with the limits of the proposed building foundation footprint, special consideration should be made as the majority of the site is likely cut and the trenches will create cut/fill transition conditions. Mitigation measures may include overexcavation of the upper 5 feet of the pad and replacement with compacted fill or backfilling the trenches with a 2-sack sand/cement slurry.

4.1.4 Shrinkage/Bulking
Based on the encountered site soils; the existing fills and upper 1 to 2 feet of the site is anticipated to shrink while the formational materials are anticipated to bulk. The preliminary estimated shrinkage and bulking factors are presented in Table 2 (in Section 2.12 of this report). The value ranges are preliminary rough estimates which will vary with depth of removal, stripping losses, field conditions at the time of grading, etc. In addition, handling losses is not included in the estimates. If possible, we suggest an area where site grades can be adjusted be provided as a balance area.

4.1.5 Temporary Excavation Stability
In general, all excavations should be performed in accordance with project plans, specifications, and all Occupational Safety and Health Administration (OSHA) requirements. Excavations should be laid back or shored in accordance with OSHA requirements before personnel or equipment are allowed to enter. Soil conditions should be mapped and frequently checked by a representative of LGC to verify conditions are as anticipated. The contractor shall be responsible for providing the “competent person” required by OSHA standards to evaluate soil conditions. Close coordination with the geotechnical engineer should be maintained to facilitate construction while providing safe excavations. Excavation safety is the responsibility of the contractor.

Temporary excavations may be cut vertically up to five feet. Excavations over five feet should be slot-cut, shored, or cut no steeper than 1:1 (horizontal to vertical) slope gradient. If a block wall along the western property line adjacent to the existing off -site building is planned, shoring of the western property line will need to be provided to for support of the wall backcut and to maintain lateral support for the off-site structure.

Surface water should be diverted away from any exposed cut, and not be allowed to pond on top of the excavations. Temporary cuts should not be left open for an extended period of time. Planned temporary conditions should be reviewed by the geotechnical consultant of record in order to reduce the potential for sidewall failure. The geotechnical consultant may provide recommendations for controlling the length of sidewall exposed.

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4.1.6 Temporary Shoring
The following preliminary geotechnical parameters may be utilized by the shoring consultant for design of the temporary shoring system along the southern property boundary, as necessary. Temporary shoring is generally considered to have a service life of two years or less. The geotechnical conditions outside of the perimeter of the proposed site have not been investigated as part of this report. The recommendations provided herein with regard to shoring of the proposed excavation are based on assumed conditions, extrapolated from the data gathered from our review of the subject site and adjacent sites. The shoring designer should independently evaluate the parameters provided and conduct an additional investigation if they consider necessary.

Prior to construction, the contractor should verify underground clearance of any existing utility lines or structures that must be removed or protected in place during construction, or may conflict with any proposed shoring system. Any tieback anchors and/or soil nails that extend beyond the site property limits will require permission from the adjacent property owner. Special attention will be required to protect existing settlement sensitive improvement in close proximity to the proposed excavation, such as any adjacent structures or streets located along the boundary of the site.

Typical cantilever temporary shoring, where deflection of the shoring will not impact the performance of adjacent structures or streets, may be designed using the active equivalent fluid pressures of 40 pounds per square foot (psf) per foot of depth (or pcf) for a level condition, and a 50 pcf for a 2:1 (horizontal to vertical) sloping condition.

Braced (i.e. internal bracing -rakers) or tied-back shoring is recommended in areas where the shoring will be located close to existing structures or streets in order to limit shoring defections or required due to the proposed depth of excavation. Braced or tied-back shoring with a level backfill may be designed using an active trapezoidal soil pressure of 24H in pounds per square foot (psf) per foot of depth (or pcf) for level condition and 30 pcf for a 2:1 (horizontal to vertical) sloping condition, where H is equal to the depth in feet of the excavation being shored (shape of the trapezoid should be 0.2H, 0.6H, 0.2H).

Any building, equipment, or traffic loads located within a 1:1 (horizontal to vertical) projection from the base of the shoring should be added to the applicable lateral earth pressure. A minimum additional uniform lateral pressure of 100 psf for the upper 10 feet should be added to the appropriate lateral earth pressures to account for typical vehicle traffic loading. The proposed shoring should be designed for a maximum shoring deflection of up to 1-inch adjacent to the street (non-surcharged condition) and up to a maximum of 0.5-inches adjacent to existing buildings (surcharged condition).

Surcharge loads on basement walls and shoring systems from existing structures located within the 1:1 (h:v) surcharge influence zone of the excavation, shoring, and basement should be determined and considered in the design.

If temporary gravity grouted tie-backs are used anchors may be designed using a preliminary bond stress of 400 pounds per square foot (psf), and if pressure/postgrouted tieback anchors are used, anchors may be designed using a preliminary bond

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stress of up to 2,500 pounds per square foot (psf). However, the tieback designer should make an independent evaluation in order to verify the preliminary bond stress is adequate for site conditions. Tieback bond stress should be verified by field testing.

Tieback anchors should be designed, constructed, and tested in accordance with the requirements of the Post-Tensioning Institute (PTI).

For design purposes, tieback should obtain their load-carrying capacity from the soil behind a plane taken to be 3 horizontal feet from the bottom of the shoring facing and inclined at an angle of 60 degrees measured from the horizontal extending to the top of the excavation. Passive resistance of soldier piles (drilled or driven) may be assumed to be an equivalent fluid pressure of 350 pcf to a maximum value of 3,500 psf. The passive earth pressure may be increased by 100 percent for isolated piles. Piles with spacing greater than 3 times of pile diameter can be considered as isolated piles. In order to develop full lateral resistance, firm contact between the soldier pile and undisturbed soils must be assured. For vertical shoring capacity, an allowable skin friction of 500 psf may be used for the portion of pier below the proposed development excavation.

End bearing should be neglected. Drilling of shafts for solider piles may require casing or drilling mud to prevent caving.

Due to the nature of the site soils, it is expected that continuous lagging between soldier piles will be required. The time between lagging excavation and lagging placement should be as short as possible. Soldier piles should be designed for the full-anticipated pressures. Due to arching in the soils, the pressure on the lagging will be less. However, it is recommended that the lagging be designed for the full design active fluid pressure but be limited to a maximum of 400 psf. Therefore, the design lagging pressure should consider a parabolic earth pressure distribution with an active equivalent fluid pressure of 40 pounds per square foot (psf) per foot of depth (or pcf) up to a maximum of 400 psf. The maximum span for lagging for this project should be 10 feet.

The components of the shoring system should be designed by a California licensed structural and/or civil engineer specializing in the design of shoring systems. Field pullout testing should be performed during construction to verify the estimated pullout resistance used in the design and/or post grout tubes should be used to ensure adequate design capacities are obtained. Ultimately, it is the specialty contractor’s responsibility to obtain the required pullout capacity, which may require design and/or field modifications. LGC should review the shoring plans prior to construction to verify that geotechnical recommendations are properly implemented into the project plans.

It is highly recommended that a program of documentation and monitoring be devised and put into practice before the onset of any groundwork. The contractor should establish survey points on the shoring, adjacent streets, and neighboring buildings within 100 feet of the excavation perimeter prior to any excavation. These survey points should be used to monitor the movement of the shoring and existing improvements during construction excavation.

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The monitoring program should include, but not necessarily be limited to detailed documentation of the existing improvements, buildings and utilities around the excavation, with particular attention to any distress that is already present prior to the start of work. A licensed surveyor should be retained to establish monuments on the shoring and the surrounding ground prior to excavation. Such monuments should be monitored for horizontal and vertical movement during construction. Results of the monitoring program should be provided immediately to the project structural (shoring) engineer and LGC for review and evaluation.

4.1.7 Fill Placement and Compaction
From a geotechnical perspective, the on-site soils are suitable for use as compacted fill, provided they are screened of rocks greater than 8-inches in maximum dimension, organic material, and construction debris. Areas prepared to receive structural fill and/or other surface improvements should be scarified to a minimum depth of 6-inches, brought to at least optimum-moisture content, and recompacted to at least 90 percent relative compaction (based on ASTM Test Method D1557). The optimum lift thickness to produce a uniformly compacted fill will depend on the type and size of compaction equipment used. In general, fill should be placed in uniform lifts generally not exceeding 8-inches in loose thickness. Placement and compaction of fill should be performed in accordance with local grading ordinances under the observation and testing of the geotechnical consultant.

If possible, imported soils should contain no materials over 3- to 8-inches in maximum dimension and have a very low to low expansion potential.

4.1.8 Trench Backfill and Compaction
The on-site soils may generally be suitable as trench backfill provided, they are screened of rocks and other material over 3- to 6-inches in diameter and organic matter.

Trench backfill should be compacted in uniform lifts (generally not exceeding 8-inches in compacted thickness) by mechanical means to at least 90 percent relative compaction (per ASTM Test Method D1557).

If trenches are shallow and the use of conventional equipment may result in damage to the utilities; clean sand, having sand equivalent (SE) of 30 or greater, should be used to bed and shade the utilities. Sand backfill should be densified. The densification may be accomplished by jetting or flooding and then tamping to ensure adequate compaction.

A representative from LGC should observe, probe, and test the backfill to verify compliance with the project specifications.

4.2 Foundation Design

4.2.1 General Foundation Selection
Recommendations for preliminary foundation design and construction are presented

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herein. Based on the results of representative expansion potential laboratory testing of the representative on-site soils, the proposed structures should be designed for a low or medium expansion potential (i.e., a 20 to 90 Expansion Index). The following post-tension and mat slab foundation recommendations are provided.

The information and recommendations presented in this section are not meant to supersede design by the project structural engineer or civil engineer specializing in the structural design nor impede those recommendations by a corrosion consultant. Should conflict arise, modifications to the foundation design provided herein can be provided.

4.2.2 Bearing Capacity
Shallow foundations may be designed for a maximum allowable bearing capacity of 2,000 lb/ft2(gross), for continuous footings a minimum of 18-inches wide and 12- inches deep; and spread footings 24-inches wide and 18-inches deep, into certified compacted fill or competent formational material. A factor of safety greater than 3 was used in evaluating the above bearing capacity value. This value may be increased by 300 psf for each additional foot in depth and 150 psf for each additional foot of width to a maximum value of 4,000 psf.

Lateral forces on footings may be resisted by passive earth resistance and friction at the bottom of the footing. Foundations may be designed for a coefficient of friction of

0.35, and a passive earth pressure of 250 lb/ft2/ft. The passive earth pressure incorporates a factor-of-safety of greater than 1.5.

All footing excavations should be cut square and level as much as possible, and should be free of sloughed materials including sand, rocks and gravel, and trash debris. Subgrade soils should be pre-moistened for the assumed medium or high expansion potential (to be confirmed at the completion of grading). These allowable bearing pressures are applicable for level (ground slope equal to or flatter than 5:1[horizontal to vertical]) conditions only.

Bearing values indicated above are for total dead loads and frequently applied live loads. The above vertical bearing may be increased by one-third for short durations of loading which will include the effect of wind or seismic forces.

4.2.3 Post-Tension Foundation
Based on our review, the site may be considered suitable for the support of the proposed structure using a post-tensioned slab-on-grade foundation system for the anticipated low to medium expansion potential. The following section summaries our recommendations for the foundation system. Table 3 contains the geotechnical recommendations for the construction of a PT slab-on-grade foundation. The structural engineer should design the foundation system based on these parameters including the foundation settlement as indicated in the following section to the allowable deflection criteria determined by the structural engineer/architect.

As indicated above, the underslab vapor/moisture retarder (i.e., an equivalent

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capillary break method) may consist of a minimum 15-mil vapor barrier in conformance with ASTM E 1745 Class A material, placed in general conformance with ASTM E1643, underlain by a minimum 1-inch of sand, as needed. The sand layer requirements above the vapor barrier are the purview of the foundation engineer/structural engineer and should be provided in accordance with ACI Publication 302 “Guide for Concrete Floor and Slab Construction”. These recommendations must be confirmed (and/or altered) by the foundation engineer, based upon the performance expectations of the foundation. Ultimately, the design of the moisture retarder system and recommendations for concrete placement and concrete mix design, which will address bleeding, shrinkage, and curling are the purview of the foundation engineer, in consideration of the project requirements provided by the architect and developer. The underslab vapor/moisture retarder described above is considered a suitable alternative in accordance with the Capillary Break Section 4.505.2.1 of the CAL Green code.

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Table 3
Preliminary Geotechnical Parameters for Post-Tensioned Foundation Design Parameter Value
Expansion Classification (Assumed to be confirmed at
the completion of grading): Low and Medium Expansion
Thornthwaite Moisture Index (from Figure 3.3): -20
Constant Soil Suction (from Figure 3.4): PF 3.6
Center Lift
Edge moisture variation distance (from Figure 3.6), em:

Center lift, ym:

Low

9.0 feet

0.35 inches
Medium

9.0 feet

0.5 inches
Edge Lift
Edge moisture variation distance (from Figure 3.6), em:

Edge lift, ym:

Low

5.2 feet

0.65 inches
Medium

5.0 feet

1.1 inches
Expansion Potential: Low
(21-50)
Medium
(51-90)
Soluble Sulfate Content for Design of Concrete Mix in
Contact with Site Soils in Accordance with American
Concrete Institute Standard 318, Section 4.3:

Negligible Exposure
(Exposure Class S0)
Corrosivity of Earth Materials to Ferrous Metals: Corrosive Modulus of Subgrade Reaction, k (assuming
presaturation as indicated below):
100 pci (low)
85 pci (medium to high)
Additional Recommendations:

1. Presaturate slab subgrade to at least 1.2 times optimum moisture to minimum depth of 12 for low expansion potential and at least 1.2 times optimum moisture to a minimum depth of 18 inches below ground surface for medium expansion potential.

2. Install a 15-mil moisture/vapor barrier in direct contact with the concrete (unless superseded by the Structural/Post-tension Engineer*) with minimum 1 inches of sand below the moisture/vapor barrier.

3. Minimum perimeter foundation embedment below finish grade for moisture cut off should be 12 and 18 inches, respectively for low and medium expansion potentials, respectively.

4. Minimum slab thickness should be 5 inches.
* The above sand and moisture/vapor barrier recommendations are traditionally included with geotechnical foundation recommendations although they are generally not a major factor influencing the geotechnical performance of the foundation. The sand and moisture/vapor barrier requirements are the purview of the foundation engineer/corrosion engineer (in accordance with ACI Publication 302 “Guide for Concrete Floor and Slab Construction”) and the homebuilder to ensure that the concrete cures more evenly than it would otherwise, is protected from corrosive environments, and moisture penetration of through the floor is acceptable to future homeowners. Therefore, the recommendations provided herein may be superseded by the requirements of the previously mentioned parties.

4.2.4 Mat Foundations
A mat foundation can be used for support of proposed residential buildings. An

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allowable soil bearing pressure of 1,500 psf may be used for the design of the mat at the surface under the slab area.
for the design of the mat at the surface under the slab area.

The allowable bearing value is for total dead loads and frequently applied live loads and may be increased by one-third for short durations of loading which will include the effect of wind or seismic forces. A coefficient of vertical subgrade reaction, k, of 85 pounds per cubic inch (pci) may be used to evaluate the pressure distribution beneath the mat foundation.

The magnitude of total and differential settlements of the mat foundation will be a function of the structural design and stiffness of the mat. Based on assumed structural loads, we estimate that total static settlement will be on the order of an inch at the center of the mat foundation. Post construction differential settlement can be taken as one-half of the maximum estimated settlement.

Resistance to lateral loads can be provided by friction acting at the base of foundations and by passive earth pressure. Foundations may be designed for a coefficient of friction of 0.35.

Coordination with the structural engineer will be required in order to ensure structural loads are adequately distributed throughout the mat foundation to avoid localized stress concentrations resulting in potential settlement. The foundation plan should be reviewed by LGC to confirm preliminary estimated total and differential static settlements.

4.2.5 Foundation Settlement
Based on our current understanding of the project, the results of our site investigation and the recommended remedial grading with shallow foundations embedded into compacted fills or competent bedrock, we estimate the post-construction static settlement of the site to be less than 1-inch with a differential settlement of approximately of 0.5-inches in 30 feet.

For buildings located above the proposed segmental wall, with a portion of the building underlain by the geogrid reinforced soils, the proposed foundation should be designed for a minimum of a medium expansion potential and for a differential settlement of up to 2-inches in 30 feet. Recommendations to reduce the potential for differential settlements in the vicinity of the segmental walls are provided herein in Section 4.4.

4.2.6 Building Clearance and Foundation Setbacks
All building foundations located close to slopes should have a minimum setback per Figure 1808.7.1 of the 2022 CBC. The setback distances should be measured from competent materials on the outer slope face, excluding any weathered and loose materials.

Per the 2022 CBC Section 1808.7.1 and Figure 1808.7.1, building clearance from the

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toe of an ascending slope should be equal one-half of the total slope height to a maximum setback of 15 feet. Retaining walls may be constructed at the base of the slope to achieve the required building clearances.

Per the 2022 CBC Section 1808.7.2 and Figure 1808.7.1, the building foundation constructed on or near a descending slope should be setback or deepened to provide a minimum footing setback equal to the total height of slope (H) divided by 3 (H/3).

The footing setback should be a minimum of 5 feet for slopes up to 15 feet in height and vary up to 40 feet for slopes up to 120 feet in height. The footing setbacks should be measured from the edge of the footing to the competent materials on the outer slope face.

4.3 Lateral Earth Pressures for Retaining Walls
The following lateral earth pressures may be used for the design of any future site retaining walls. Due to the expansive nature of some of the on-site clayey formational materials, we recommend site retaining walls be backfilled with either the very low expansive bedrock or sandy soils (with minus 3-inch rock) or approved select soils. Approved select soils should consist of clean, granular soils (less than 15 percent passing the No. 200 sieve) of very low expansion potential (expansion index 20 or less based on UBC. 18-2). The recommended lateral pressures for approved select soils for level or sloping backfill are presented in Table 4.

Table 4
Lateral Earth Pressures for Retaining Walls
Conditions
Equivalent Fluid Weight (pcf)
Level Backfill 2:1 Backfill Sloping
Upwards Dynamic Load
Increment
(pcf) * Approved Select
Material
Approved Select
Material
Active 35 50 Level -10H
2 2H:1V - 17H
2 At Rest 55 80 16H
2 Passive 250 -- --
* For walls with greater than 6-feet in backfill height, the above seismic earth pressure should be added to the static pressures given in the table above. The seismic earth pressure should be considered as a triangular distribution with the resultant acting at 0.4H in relation to the base of the retaining wall footing (where H is the retained height). The incremental seismic load was determined in general accordance with the standard of practice in the industry for determining earth pressures as a result of seismic events.

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For design purposes, the recommended equivalent fluid pressure for each case for walls founded above the static ground water and backfilled with approved select soils is provided in Table 4. The equivalent fluid pressure values assume free-draining conditions. If conditions other than those assumed above are anticipated, the equivalent fluid pressure values should be provided on an individual-case basis by the geotechnical engineer. Surcharge loading effects from the adjacent structures should be evaluated by the geotechnical and structural engineers.

Retaining wall structures should be provided with appropriate drainage and appropriately waterproofed. The outlet pipe should be sloped to drain to a suitable outlet. Typical wall drainage design is illustrated in Figure 3. It should be noted that the recommended subdrain does not provide protection against seepage through the face of the wall and/or efflorescence.

Efflorescence is generally a white crystalline powder (discoloration) that results when water, which contains soluble salts, migrates over a period of time through the face of a retaining wall and evaporates. If such seepage or efflorescence is undesirable, retaining walls should be waterproofed to reduce this potential.

Lateral earth pressures are provided as equivalent fluid unit weights, in psf/ft of depth or pcf.

These values do not contain an appreciable factor of safety. A soil unit weight of 120 pcf may be assumed for calculating the actual weight of soil. For sliding resistance, a friction coefficient of 0.35 may be used at the concrete and soil interface. Wall footings should be designed in accordance with structural considerations. Refer to Section 4.2.2 for passive resistance and allowable soil bearing.

4.4 Segmental Retaining Wall Recommendations
Segmental retaining walls that may be constructed on the site are anticipated to have a level or up to a 2:1 (horizontal to vertical) sloping backfill above the walls. The zone of influence for geogrid-reinforced modular block walls is defined by a 1:1 (horizontal to vertical) projection from the heel of the bottom geogrid to the finished ground surface overlying the wall. Any building or vehicle loads within this zone should be considered in the wall design.

The following geotechnical parameters presented in Table 5 may be utilized by the wall engineer in design of the on-site segmental walls. Design of segmental retaining walls should be per the National Concrete Masonry Association (NCMA) guidelines (or equivalent guidelines).

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Table 5
Design Soil Strength Parameters for Segmental Retaining Walls Cohesion (psf)
Friction Angle
Peak/Ultimate
(Degrees)
Unit Weight (pcf)
Infill (Reinforced) Soil 50 35/30 120
Retained (Backfill) Soil 100 35/30 120
Foundation Soil 100 35/30 120
The design acceleration of 0.411g (or 2/3 PGAm), should be used for the proposed design. A Pseudo-Static Coefficient of 0.28g should be used for Slope Stability Analysis. Once the wall designer designs the wall considering external, internal, and local wall stability, LGC will then check the global slope stability. Where global slope stability is the controlling factor, additional geogrid will be added to the design and/or the geogrid will be lengthened, as needed. Thus, the final design is expected to satisfy both the “conventional method” of modular wall design as well as global slope stability.

All excavations should be made in accordance with Cal OSHA, as a general guideline. The backfill soils (having an expansion index less than 30 per UBC. 18-I-B) should be compacted to at least 90 percent relative compaction (based on ASTM Test Methods D2922 and D3017). The walls should be constructed and backfilled as soon as possible after back-cut excavation.

Prolonged exposure of back-cut slopes may result in some localized slope instability.

Excavation safety is the sole responsibility of the contractor.

The subject walls may be backfilled using the on-site native soils. For closed face walls we recommend a minimum 1-foot-wide drainage gallery be constructed immediately behind the face of the wall using Class II Permeable material and augmented with a perforated 4-inch PVC pipe, or per the wall manufactures specifications. This drainage layer and drain is not a requirement for open faced walls. The remainder of the wall may be backfilled using the onsite native soils. The subject segmental retaining walls should be constructed founded onto competent soils (i.e., compacted fills or competent native soils), or per manufactures specifications. For preliminary purposes, the allowable bearing capacities to be used in the wall design is 1,500 pounds per square foot.

From a geotechnical perspective, the on-site soils are generally suitable for use as compacted fill, provided they are screened of rocks greater than 8 inches in maximum dimension, organic materials, and construction debris. Fill soils should be brought to at least optimum-moisture content, and recompacted to at least 90 percent relative compaction (based on ASTM Test Method D1557). The optimum lift thickness to produce a uniformly compacted fill will depend on the type and size of compaction equipment used. In general, fill should be placed in uniform lifts generally not exceeding 8 inches in compacted thickness. Placement and compaction of fill should be performed in accordance with local grading ordinances under full-time observation

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and testing of the geotechnical consultant. The geotechnical consultant shall review and approve all fill materials, including on-site and import materials.

Prior to placement of the geogrid, the surface of the compacted fill shall be prepared such that it has a maximum variation of 6 vertical inches over a distance of 15 feet. Each geogrid layer shall be pulled taut and secured in-place prior to placing backfill material on the geogrid. The geogrid layers shall be continuous and no splice and/or connection system will be accepted. The contractor shall not operate tracked construction equipment directly upon the geogrid reinforcement but shall use rubber tired equipment. All passes with tracked equipment for the purposes of obtaining compaction shall be done in straight lines and shall minimize the turning movements of the equipment to reduce the potential for displacing and/or damaging the geo-grids.

The manufacturer shall provide the owner with quality control testing for each lot of blocks which are shipped to the site. The contractor shall install the block per the manufacturer’s recommended procedures.

All excavations should be made in accordance with Cal OSHA, as a general guideline. All excavations should be made at 1:1 inclinations or flatter. Once excavation has been initiated, the segmental retaining wall should be constructed as soon as possible after back-cut excavation. Prolonged exposure of back-cut slopes may result in some localized slope instability. Excavations should be planned so that they are not initiated without sufficient time to backfill them prior to weekends, holidays, or forecasted rain. Excavation safety is the sole responsibility of the contractor.

We recommend the contractors proposed plan of operations be reviewed by this office prior to initiation of work and closely monitored by representatives of this office during excavation and construction.

A backdrain should be installed at the heel of the wall back-cut consisting of a 4-inch PVC pipe surrounded by ¾-inch crushed rock and wrapped in a filter fabric and outletted through the wall face or to another suitable outlet. If water seepage is encountered along the wall back-cut, a continuous chimney drain consisting of a one-foot layer Caltrans Class II permeable material shall be placed at the heel along the back-cut behind the geogrid, as necessary. The chimney drains should be outletted through the backdrain at the heel of the cut. The outlet pipes should be constructed at the low points of the subdrains and have a minimum 2 percent fall to the outlet location. Additional subdrains may be needed if seepage and/or areas of potential seepage are encountered during grading operations.

Positive drainage of surface water away from the base and top of the proposed segmental retaining walls are important. A concrete V-ditch shall be constructed behind the top of each of the proposed walls to prevent surface water from infiltrating the backfill soil. The V-ditch shall be designed and placed by the project civil engineer in accordance with the local codes.

Where proposed residential structures are located above the proposed segmental walls, where the proposed reinforced zones will encroach into the proposed buildings, the following recommendations should be considered in the design and site construction. The fill behind the wall within the reinforced zone should be comprised of on-site sandy granular soils with

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a low expansion potential. Sandy/granular soils will interlock with the geogrid layers which is expected to reduce the potential for long-term, creep-type lateral deformation of the segmental wall, beyond the initial elastic deformation. As a result, the long-term differential settlement potential behind/above the segmental wall is expected to be reduced. Further, the backcut for wall construction should be excavated at a gradient no steeper than 2:1 (horizontal to vertical). This will help reduce the differential fill thickness beneath the proposed structures. The fills outside the reinforced zone should also consist of soils with relatively low expansion potentials and should be compacted to a minimum 93 percent relative compaction.

4.5 Soldier Pile Wall Recommendations
The following preliminary geotechnical parameters may be utilized by the soldier pile wall consultant for design of the permanent wall system. The recommendations provided herein with regard to the proposed wall design are based on assumed conditions, extrapolated from the data gathered from our site investigation and geotechnical analysis. The wall designer should independently evaluate the parameters provided and conduct an additional investigation if they consider necessary.
based on assumed conditions, extrapolated from the data gathered from our site investigation and geotechnical analysis. The wall designer should independently evaluate the parameters provided and conduct an additional investigation if they consider necessary.

Typical cantilever soldier pile wall design, where deflection of the wall will not impact the performance of adjacent structures or streets, may be designed using the active equivalent fluid pressures of 40 pounds per square foot (psf) per foot of depth (or pcf). Restrained walls (with soil nails or tied-back) is recommended to limit defections or required due to the proposed wall height. Restrained or tied-back shoring with a level backfill may be designed using an active trapezoidal soil pressure of 38H in pounds per square foot (psf), where H is equal to the depth in feet of the wall (shape of the trapezoid should be 0.2H, 0.6H, 0.2H) or may be designed using an active triangular soil pressure of 60 pounds per square foot (psf).

Any building, equipment, or traffic loads located within a 1:1 (horizontal to vertical) projection from the base of the wall should be added to the applicable lateral earth pressure.

A minimum additional uniform lateral pressure of 100 psf for the upper 10 feet should be added to the appropriate lateral earth pressures to account for typical vehicle traffic loading. the appropriate lateral earth pressures to account for typical vehicle traffic loading. he appropriate lateral earth pressures to account for typical vehicle traffic loading.

A seismic earth pressure of 17 pcf should be added to the static pressures given in Table 4 above. The seismic earth pressure should be considered as an inverted triangular distribution with the resultant acting at 0.6H in relation to the base of the retaining wall footing (where H is the retained height).

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Passive resistance of soldier piles may be assumed to be an equivalent fluid pressure of 350 pcf for level and 150 pcf for sloping down conditions to a maximum value of 3,500 psf. The passive earth pressure may be increased by 100 percent for isolated piles. Piles with spacing greater than 3 times of pile diameter can be considered as isolated piles. In order to develop the full lateral resistance, firm contact between the soldier pile and undisturbed soils must be assured. For vertical capacity, an allowable skin friction of 500 psf may be used for the embedded depth. End bearing should be neglected.

4.6 Preliminary Pavement Recommendations
Preliminary pavement sections utilizing asphalt concrete (AC), Portland Cement Concrete Pavement PCCP), and vehicular concrete pavers, are presented in the following sections.

4.6.1 Asphalt Concrete (AC) Pavement
Based on an assumed R-value of 7 (obtained during the preliminary investigation of an adjacent property), we utilized an assumed R-Value of 7 and recommend the following preliminary minimum street sections for Traffic Indices of 5, 6, and 7 (as indicated in Table 6). These recommendations should be confirmed with R-value testing of representative near-surface soils at the completion of grading. Final AC sections should be confirmed by the project civil engineer based upon the projected Traffic Index. In addition, additional sections can be provided based on other traffic indices.

Table 6
Preliminary AC Pavement Design Sections
Assumed Traffic Index 5 6 7
R-Value Subgrade 7 7 7
AC Thickness 4.0 inches 4.0 inches 4.0 inches
Aggregate Base Thickness 7.0 inches 12.0 inches 15.0 inches The aggregate base material should conform to the specifications for Crushed Aggregate Base or Crushed Miscellaneous Base (Standard Specifications for Public Works Construction –SSPWC Section 200-2). The subgrade should achieve a minimum relative compaction of 95 percent. The base material should be compacted to achieve a minimum relative compaction of 95 percent. Aggregate base and subgrade materials should be moisture-conditioned to a relatively uniform moisture content at or slightly over optimum.

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4.6.2 Portland Cement Concrete Pavement
Portland Cement Concrete Pavement (PCCP) may be designed using a minimum of 8- inches of Portland Cement Concrete over 8-inches of compacted aggregate base.

The modulus of rupture of the PCCP should be a minimum of 500 pounds per square inch (psi) at 28 days. Contraction joints should be placed at maximum 15-foot spacing.

Where the outer edge of a concrete pavement connects to an asphalt pavement, the concrete slab should be thickened by 50 percent at a taper not to exceed a slope of 1 in

10. In addition, additional sections can be provided based on other desired anticipated traffic loadings.

The aggregate base material should conform to the specifications for Crushed Aggregate Base or Crushed Miscellaneous Base (Standard Specifications for Public Works Construction - SSPWC Section 200-2). The subgrade should achieve a minimum relative compaction of 95 percent. The base material should be compacted to achieve a minimum relative compaction of 95 percent. Base and subgrade materials should be moisture-conditioned to a relatively uniform moisture content at or slightly over optimum.

4.6.3 Vehicular Concrete Paver Pavement
Typical vehicular pavers are 3-1/8 inches in thickness and the manufacturers usually recommend that the pavers be underlain by a 1-inch-thick sand layer. Based on ASCE 58-10 for interlocking pavers and considering a Traffic Index (TI) of 6 and an R-Value of 7 for the subgrade soils, we recommend that the vehicular pavers and sand layer be underlain by a minimum of 16-inches of aggregate base.

The aggregate base material should conform to the specifications for Crushed Aggregate Base or Crushed Miscellaneous Base (Standard Specifications for Public Works Construction –SSPWC Section 200-2). The subgrade should achieve a minimum relative compaction of 95 percent per ASTM- D1557. The base material should be compacted to achieve a minimum relative compaction of 95 percent. Base and subgrade materials should be moisture-conditioned to a relatively uniform moisture content at or slightly over optimum.

4.7 Nonstructural Concrete Flatwork
Preliminary nonstructural concrete flatwork designs are presented in the following sections.

Portland Cement Concrete (PCC) flatwork (such as sidewalks, walkways, patios, entryways, etc.) have a high potential for cracking due to changes in soil volume related to soil-moisture fluctuations because these slabs are typically much thinner than foundation slabs and are not reinforced with the same dynamics as foundation elements. To reduce the potential for excessive cracking and lifting, concrete may be designed in accordance with the minimum guidelines outlined in Table 7. These guidelines will reduce the potential for irregular cracking and promote cracking along construction joints but will not eliminate all cracking

Page 1092 of 1727 ends

Project No. 244006-01 Page 32 August 15, 2024
or lifting. Thickening the concrete and/or adding reinforcement will further reduce cosmetic distress.

Table 7
Nonstructural Concrete Flatwork
Private Sidewalks Patio/Entryways
Minimum Thickness
(in inches) 4 5
Presaturation Presoak to 12-inches prior
to placement
Presoak to 12-inches prior
to placement
Reinforcement --
No. 3 at 24 inches on
centers or 6x6 No. 6 by No.
6 Welded Wire Mesh
Crack Control
Saw cut or deep tool joint
to a minimum of 1/3 the
concrete thickness
Saw cut or deep tool joint
to a minimum of 1/3 the
concrete thickness
Maximum Joint Spacing 5 feet 6 feet
Aggregate Base -- 2 inches

4.8 Corrosivity to Concrete and Metal
The National Association of Corrosion Engineers (NACE) defines corrosion as “a deterioration of a substance or its properties because of a reaction with its environment.” From a geotechnical viewpoint, the “environment” is the prevailing foundation soils and the “substances” are the reinforced concrete foundations or various buried metallic elements such as rebar, piles, pipes, etc., which are in direct contact with or within close vicinity of the foundation soil.

In general, soil environments that are detrimental to concrete have high concentrations of soluble sulfates and/or pH values of less than 5.5. ACI 318R-14 Table 19.3.1.1, provides specific guidelines for the concrete mix design when the soluble sulfate content of the soils exceeds 0.1 percent by weight or 1,000 ppm. The minimum amount of chloride ions in the soil environment that are corrosive to steel, either in the form of reinforcement protected by concrete cover, or plain steel substructures such as steel pipes or piles, is 500 ppm per California Test 532.

Laboratory testing of representative on-site soils indicated that the on-site soils tested are

Page 1093 of 1727 ends

Project No. 244006-01 Page 33 August 15, 2024
classified as having a Sulfate Exposure Class of S0 (per Table 19.3.1.2 of the ACI 318-19).

As a preliminary recommendation, concrete in contact with on-site soils should be designed in accordance with ACI 318-19 Table 19.3.2.1 for the S0/negligible or not applicable category. It is also our opinion that on-site soil should be considered moderately corrosive to buried metals. Site grading will redistribute the materials, which may result in soils with different corrosion potentials. Therefore, the as-graded soil conditions should be verified with confirmatory sampling and testing during the grading phase of the project.

Despite the minimum recommendation above, LGC is not a corrosion-engineering firm.

Therefore, we recommend that after site grading, consultation with a competent corrosion engineer be initiated to evaluate the actual corrosion potential of the site and to provide recommendations to reduce the corrosion potential with respect to the proposed improvements, as necessary. The recommendations of the corrosion engineer may supersede the above requirements.

4.9 Freestanding Walls
Freestanding wall footings should be founded a minimum of 24-inches below the lowest adjacent grade. To reduce the potential for unsightly cracks, we recommend inclusion of construction joints at 10- to 20-foot intervals.

Due to the potential creep of soils, where free standing walls are constructed close to a topof-slope, some tilt of the wall should be anticipated. To reduce the amount of tilt, a combination of grade beam and caisson foundations may be used to support the wall. The system should consist of a minimum of 12-inch diameter caissons placed at 8 feet maximum on centers, and each 8 feet long and connected together at top with 12-inch by 12-inch grade beam.

4.10 Control of Surface Water and Drainage Control
Positive drainage of surface water away from structures is very important. No water should be allowed to pond adjacent to buildings. Positive drainage may be accomplished by providing drainage away from the building at a gradient of at least 2-percent for a distance of at least 5 feet, and further maintained by a swale or drainage path at a gradient of at least 1-percent.

Where necessary, drainage paths may be shortened by use of area drains and collector pipes.

Planters with open bottoms adjacent to buildings should be avoided. Planters should not be designed adjacent to buildings unless provisions for drainage, such as catch basins, liners, and/or area drains, are made. Overwatering must be avoided.

4.11 Construction Observation and Testing
The recommendations provided in this report are based on limited subsurface observations and geotechnical analysis. The interpolated subsurface conditions should be checked in the field during construction by a representative of LGC.

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Project No. 244006-01 Page 34 August 15, 2024
Geotechnical observation and testing should be performed by the geotechnical consultant during site excavations, subgrade for slab/foundation, backfill of utility trenches, preparation of any subgrade and placement of aggregate base, or when any unusual soil conditions are encountered at the site. Grading plans, foundation plans, and final project drawings should be reviewed by this office prior to construction.

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5.0 LIMITATIONS
Our services were performed using the degree of care and skill ordinarily exercised, under similar circumstances, by reputable engineers and geologists practicing in this or similar localities. No other warranty, expressed or implied, is made as to the conclusions and professional advice included in this report. The samples taken and submitted for laboratory testing, the observations made, and the in-situ field testing performed are believed representative of the entire project; however, soil and geologic conditions revealed by excavation may be different than our preliminary findings. If this occurs, the changed conditions must be evaluated by the project soils engineer and geologist and design(s) adjusted as required or alternate design(s) recommended.

This report is issued with the understanding that it is the responsibility of the owner, or of his/her representative, to ensure that the information and recommendations contained herein are brought to the attention of the architect and/or project engineer and incorporated into the plans, and the necessary steps are taken to see that the contractor and/or subcontractor properly implements the recommendations in the field. The contractor and/or subcontractor should notify the owner if they consider any of the recommendations presented herein to be unsafe.

The findings of this report are valid as of the present date. However, changes in the conditions of a property can and do occur with the passage of time, whether they be due to natural processes or the works of man on this or adjacent properties.

In addition, changes in applicable or appropriate standards may occur, whether they result from legislation or the broadening of knowledge. Accordingly, the findings of this report may be invalidated wholly or partially by changes outside our control.

Page 1096 of 1727 ends

1 2
3 4
5 7
6 8
91011 28 29 30 31 32 33 34 35 36 37 38 40 41 42 43 16 15 14 13 12 21 20 19 18 39 252627 242322 17 B-4 B-5 B-6 TD=10.5' TD=10.5' TD=10.5' L-B-1 L-B-2 TD=56' N-B-2TD=? B-1 B-3 TD=20.5' TD=20.5' B-2 TD=11.0' ?
?
?
?
? TD=60' Ts Ts Ts Ts Afo Ts Ts N-B-2 30N36W @10.0' 33N68W @13.9' 5N48W @22.5'
5 ?
N65E @53.0'
?
? Afo Afo Ts Ts Ts
?
?
?
?
? Legend Afo Artificial Older Fill Ts Tertiary-aged Sespe Formation, circled where buried Approximate limits of fill, queried where uncertain Approximate Boring Location by LGC Valley (2024)Approximate Boring Location by Lawmaster & Co. (1986)Approximate Boring Location by G. A. Nichol (1986)Approximate Bedding Attitude Base Map: 2024-07-30, Site Plan Laguna Hills Mill Creek 2.4 Acre Site, Sheet 1 of 1, by Wilson Mikami Corporation.

Geotechnical Map 23161 Mill Creek Drive Laguna Hills, California 244006-01 Toll/23161 Mill Creek BIH/RKW 1" = 50' August 15, 2024 Project Name Project No. Eng. / Geol. Scale Figure 2 Date 0 25 50 100
? B-6 TD=10.5' L-B-2 TD=60' N-B-2 TD=? 33N68W

Page 1097 of 1727 ends

FENCE

WALL HEIGHT, H

EXTENT OF FREE DRAINING SAND BACKFILL, MINIMUM
HEEL WIDTH OR H/2 WHICH EVER IS GREATER

BACKCUT PER OSHA
1' MINIMUM

WATER PROOFING PER CIVIL ENGINEER

FOOTING/WALL DESIGN PER CIVIL ENGINEER
MINIMUM 1 CUBIC FOOT PER LINEAR FOOT

BURRITO TYPE SUBDRAIN, CONSISTING OF
3/4 INCH CRUSHED ROCK WRAPPED IN
MIRAFI 140N OR APPROVED EQUIVALENT

NATIVE BACKFILL COMPACTED
TO MINIMUM 90% RELATIVE
COMPACTION PER ASTM1557-D

FREE DRAINING SAND BACKFILL
SE 30 OR GREATER
4 INCH DIAMETER, SCHEDULE 40 PERFORATED

PVC PIPE TO FLOW TO DRAINAGE DEVICE
Project Name
Eng. / Geol.

Date
Scale
Project No.

Backfill
Detail, Sand
Retaining Wall
Figure 3:

August 15, 2024
Not-To-Scale

BIH/RKW
244006-01
Toll/Laguna Hills

Page 1098 of 1727 ends

Project No. 244006-01 Page A-1 August 15, 2024

APPENDIX A
References
American Concrete Institute (ACI), 1985, Manual of Concrete Practice, Parts 1 and 2.

American Concrete Institute (ACI), 2019, Building Code Requirements for Structural Concrete (ACI 318-19) and Commentary, an ACI Standard, reported by ACI Committee 318.

American Society of Civil Engineers (ASCE), 2017, Minimum Design Loads for Buildings and Other Structures, ASCE/SEI 7-16, with Supplement 1, Effective December 12, 2018.

ASCE 7 Hazard Tool, https://asce7hazardtool.online/, accessed August 2024.

Bock & Clark Corporation, 2022, ALTA/NSPS Land Title Survey Map, Project No. 202201282-005 AAC, dated May 23, 2022.

California Building Standards Commission, 2022, California Building Code, California Code of Regulations Title 24, Volumes 1 and 2, dated July 2022.

California Department of Conservation Geologic Energy Management Division (CalGEM), 2023, Well Finder at https://www.concervation.ca.gov/calgem/Pages/WellFinder.aspx, accessed May 2024.

California Department of Water Resources (CDWR), 2023, Water Data Library (WDL) Station Map, at https://wdl.water.ca.gov, accessed May 2024.

CDWR, 2023, Sustainable Groundwater Management Act (SGMA) Data Viewer, at https://sgma.water.ca.gov/webgis/?appid=SGMADataViewer#gwlevels, accessed May 2024.

California Geological Survey (CGS), 1997, Guidelines for Evaluating and Mitigating Seismic Hazards in California, dated March 13, 1997, SP 117.

CGS, 2001, Earthquake Zones of Required Investigation, San Juan Capistrano Quadrangle, dated December 21, 2001.

CGS, 2006, Seismic Hazard Zone Report for the San Juan Capistrano 7.5-minute Quadrangle, Orange County, California, Seismic Hazard Zone Report 053, dated 2000, revised January 17, 2006.

CGS, 2018, Earthquake Fault Zones; A Guide for Government Agencies, Property Owners/Developers, and Geoscience Practitioners for Assessing Fault Rupture Hazards in California, Special Publication 42, dated January 2018.

CGS, 2023, California Earthquake Hazards Zone Application (EQ Zapp) Online Map at https://maps.conservation.ca.gov/cgs/EQZApp/app/, accessed August 2024.

Page 1099 of 1727 ends

Project No. 244006-01 Page A-2 August 15, 2024
References (continued)
California State Water Resources Control Board (CSWRCB), 2023, GeoTracker at https://geotracker.waterboards.ca.gov, accessed August 2024.

EJN & Associates, Inc., 1986, Preliminary Soils Investigation, Tentative Parcel Map No. 85-367, Orange County, California, Job No. 86-155-1, dated March 18, 1986.

EJN Geotechnical, 1988, Final Compaction Report, Landmark Lake Hills, 23422 Mill Creek Drive, Laguna Hills, California, Grading Permit No. 86-146836, Job No. 86-155, dated March 2, 1988.

Google Earth at https://earth.google.com, accessed May 2024.

Google Maps and Street View at https://www.googlemaps.com, accessed May 2024.

Historical Aerials, 2023, Historical Aerial Photographs from 1946 and Historical Topography Maps from 1896, at https://www.historicalaerials.com, accessed May 2024.

Irvine Soils Engineering Inc., 1983a, Geotechnical Investigation, Proposed Two (2) Three-Story Office Buildings, Mill Creek Drive, Lots 9 and 10, Laguna Hills, California, Job No. 2405-00, dated June 10, 1983, revised July 25, 1983.

Irvine Soils Engineering Inc., 1983b, Soils Compaction Report, Rough Grading, Retaining Wall Grading, 23272 Mill Creek Road, Laguna Hills, California, Grading Permit No. 424,854, Job No. 2405-10, dated December 19, 1983.

Ishihara, K., 1985, “Stability of Natural Deposits During Earthquakes”. Proceedings of the Eleventh International Conference on Soil Mechanics and Foundation Engineering. A.A. Bakema Publishers, Rotterdam, Netherlands.

Jennings, C.W., and Bryant, W.A., 2010a, Fault Activity Map of California: California Geological Survey Geologic Data Map No. 6, Scale 1:750,000.

Jennings, C.W., and Bryant, W.A., 2010b, An Explanatory Text to Accompany the 2010 Fault Activity Map of California, 98 p.

Jennings, C.W., Gutierrez, C., Bryant, W., Saucedo, G., and Wills, C., 2010, Geologic Map of California, CGS Geologic Data Map 2, Scale: 1:750,000.

Lawmaster & Co., Inc, 1986, Geotechnical Investigation, Proposed Office Building (Mill Creek Plaza), 23091 Mill Creek Drive, Laguna Hills, California, File No. 86-10789, dated June 24, 1986.

Lawmaster & Co, Inc., 1989, Laguna Hills Office Building, Responses to Orange County Geologic Review Sheet dated July 14, 1989, File No. 89-11524-R, dated July 21, 1989.

Page 1100 of 1727 ends

Project No. 244006-01 Page A-3 August 15, 2024
References (continued)
LGC Valley, Inc., 2024a, Preliminary Geotechnical Investigation, Proposed Residential Development, 23272 and 23282 Mill Creek Drive, Laguna Hills, California, Project No. 233016-01, dated November 17, 2023, revised January 16, 2024.

LGC Valley Inc., 2024b, Geotechnical Due Diligence Review of the 23161 Mill Creek Drive, Assessor Parcel Number 588-142-07, Laguna Hills, California, Project No. 244006-01, dated May 28, 2024.

Morton, D.M., Hauser, R.M., and Ruppert, K.R., 1999, Preliminary digital geologic map of the Santa Ana 30' X 60' quadrangle, southern California, U.S. Geological Survey, Open-File Report OF99-172, Scale 1:100,000.

Morton, D.M. and Miller, F.K., 2006, Geologic Map of the San Bernardino and Santa Ana 30’x60’ Quadrangle, USGS OFR-2006-1217, Scale 1:100,000.

Morton, P.K., Miller, R.V., and Evans, J.R., 1976, Environmental Geology of Orange County, California., California Division of Mines and Geology, Open-File Report OFR-79-08, Scale 1:48,000.

National Association of Corrosion Engineers (NACE), 1984, Corrosion Basics: An Introduction, 353 pages.

Post-Tensioning Institute, 2010, Design of Post Tensioned Slabs-on-Ground, Third Addition, Addendum 1 dated May 2007, and Addendum 2 dated May 2008, with Errata February 4, 2010.

Pradel, D., 1998, “Procedure to Evaluate Earthquake Induced Settlements in Dry Sandy Soils”, Journal of Geotechnical and Geoenvironmental Engineering, Vol. 124, No. 4, April 1998.

Sadigh, K., Chang, C.-Y., Egan, J.A., Makdisi, F., and Youngs, R.R. (1997), "Attenuation Relations for Shallow Crustal Earthquakes Based on California Strong Motion Data," Seismological Research Letters, Vol. 68, No. 1, pp. 180-189.

Secor International Inc., 1997, Final Quarterly Groundwater Monitoring, 23552 Moulton Parkway, Laguna Hills, California, 92653, OCHCA Case # 96UT13, 24 p., dated February 20, 1997.

Seed, H.B., Tokimatsu, K., Harder, L.F., and Chungh, R.M., 1985, “Influence of SPT Procedures in Soil Liquefaction Resistance Evaluations,” Journal of Geotechnical Engineering, Vol. 111, No. 12, December 1985.

United States Geological Survey (USGS), 2008, “2008 National Seismic Hazard Maps – Fault Parameters” at https://earthquake.usgs.gov/cfusion/hazfaults_2008_search/query_main.cfm, accessed October 2023.

USGS, 2013, U.S. Seismic Design Maps, at
http://geohazards.usgs.gov/designmaps/us/batch.php#csv, accessed August 2024.

Page 1101 of 1727 ends

Project No. 244006-01 Page A-4 August 15, 2024
References (continued)
USGS, 2014, “2008 Interactive Deaggregations (Beta),” at: https://geohazards.usgs.gov/deaggint/2008/, accessed August 2024.

USGS and CGS, 2020, Quaternary Fault and Fold Database of the United States at https://www.usgs.gov/programs/earthquake-hazards/faults, last update September 2, 2020, accessed August 2024.

Wilson Mikami Corporation, 2024, Site Plan, Laguna Hills Mill Creek 2.4 Acre Site, Sheet 1 of 1, dated July 30, 2024.

Page 1102 of 1727 ends

Project No. 244006-01 Page B-1 August 15, 2024

APPENDIX B
Geotechnical Boring Logs (Current Study)

Page 1103 of 1727 ends

0 5
10 298
293
288Elevation (ft) Depth (ft) Graphic Log Sample Number Blow Count Dry Density (pcf) Moisture (%) USCS Symbol

DESCRIPTION
Logged By: MET
Sampled By: MET Type of Test
Date:

Project Name:

Drilling Company:

Drive Weight:

Elevation of Top of Hole:

Project Number:

Type of Rig:

Drop:

Hole Location:

Hole Dia:

Page:

Geotechnical Boring Log
= Ring Sample
= SPT
THIS SUMMARY APPLIES ONLY AT THE LOCATION OF THIS BORING AND AT THE TIME OF DRILLING. SUBSURFACE CONDITIONS MAY DIFFER AT OTHER LOCATIONS AND MAY CHANGE AT THIS LOCATION WITH THE PASSAGE OF TIME. THE DATA PRESENTED IS A SIMPLIFICATION OF THE ACTUAL CONDITIOND ENCOUNTERED. LGC VALLEY, INC.

B-1
May 8, 2024 1 of 1
Toll/23161 Mill Creek
Martini Drilling
140 pounds
+298 Feet
244006-01
Hollow Stem Auger
30 inches
See Geotechnical Map
8 inches
@ 0' 4.5-inches of asphalt concrete over
8-inches of aggregate base
Sespe Formation (Ts):
@ 5' Silty fine to medium sandy CLAYSTONE
to silty fine to coarse SANDSTONE, very minor
gravel; dark brown to red brown, damp, hard
to very dense
Total Depth = 20.5 Feet
No Ground Water Encountered
Backfilled 5/8/2024
with Native Soil and Concrete Plug
Artificial Fill, Older (Afo):
@ 1' Silty to clayey fine to medium SAND,
very minor gravel; red brown to dark brown,
damp, medium dense
SM
1 2
50/6"
50/6"
B1
@1'-5'
110.9 6.9 CL/SM
15283
20278
3 50/2"
@ 6' Silty fine to medium SANDSTONE, very
minor gravel; red brown, damp, very dense
@ 10' Silty fine to medium SANDSTONE,
minor gravel; pale red brown, slightly damp,
very dense; sample disturbed - rock in
sampler
4 50/6"
5 50/4"
@ 15' Silty fine to medium SANDSTONE,
minor gravel; red brown, damp, very dense
SM
B2
@10'-15'
COR,
AL, EI
DS
110.5 8.2
114.2 2.0
Project No. 244006-01 Figure B - 1 August 15, 2024

Page 1104 of 1727 ends

0 5
10 306
301
296Elevation (ft) Depth (ft) Graphic Log Sample Number Blow Count Dry Density (pcf) Moisture (%) USCS Symbol

DESCRIPTION
Logged By: MET
Sampled By: MET Type of Test
Date:

Project Name:

Drilling Company:

Drive Weight:

Elevation of Top of Hole:

Project Number:

Type of Rig:

Drop:

Hole Location:

Hole Dia:

Page:

B-2
May 8, 2024 1 of 1
Toll/23161 Mill Creek
Martini Drilling
140 pounds
+306 Feet
244006-01
Hollow Stem Auger
30 inches
See Geotechnical Map
8 inches
50/6" 111.3 1
@ 0' 5.5-inches of asphalt concrete over
6-inches of aggregate base
@ 5' Becomes a very silty fine to medium

SANDSTONE
Total Depth = 11 Feet
No Ground Water Encountered
Backfilled 5/8/2024
with Native Soil and Concrete Plug
Sespe Formation (Ts):
@ 1' Silty fine to medium SANDSTONE, very
minor gravel; red brown, damp, very dense

14.0 SM
2 3
86/8.5"
88/9" @ 10' Silty fine SANDSTONE to fine sandy
SILTSTONE; red brown to dark red brown,
damp, very dense to hard
SM/ML
B1
@1'-6'
111.7 12.4
116.0 12.2
Project No. 244006-01 Figure B - 2 August 15, 2024

Page 1105 of 1727 ends

0 5
10 15
20 297
292
287
282
277Elevation (ft) Depth (ft) Graphic Log Sample Number Blow Count Dry Density (pcf) Moisture (%) USCS Symbol

DESCRIPTION
Logged By: MET
Sampled By: MET Type of Test
Date:

Project Name:

Drilling Company:

Drive Weight:

Elevation of Top of Hole:

Project Number:

Type of Rig:

Drop:

Hole Location:

Hole Dia:

Page:

B-3
May 8, 2024 1 of 1
Toll/23161 Mill Creek
Martini Drilling
140 pounds
+297 Feet
244006-01
Hollow Stem Auger
30 inches
See Geotechnical Map
8 inches
1 69
@ 0' 5.5-inches of asphalt concrete over
8-inches of aggregate base
Total Depth = 20.5 Feet
No Ground Water Encountered
Backfilled 5/8/2024
with Native Soil & Concrete Plug
Artificial Fill, Older (Afo):
@ 1.1' Silty fine to coarse SAND, minor gravel
and minor clay; red brown, damp, medium
dense
SM
2 3
4 5
6 82
50/5"
@ 10' Increase in coarse sand
@ 20' Decrease in coarse sand
@ 5' Silty fine to coarse SANDSTONE, very
minor gravel; red brown, damp, dense
B1
@1'-6'
50/6"
50/6"
50/5"
SM
Sespe Formation (Ts):
@ 2.5' Silty fine to coarse SANDSTONE, very
minor gravel and minor clay; red brown,
damp, dense
119.3 5.7
119.6 4.2
119.1 7.5
110.4 5.7
Project No. 244006-01 Figure B - 3 August 15, 2024

Page 1106 of 1727 ends

0 5
10 308
303
298Elevation (ft) Depth (ft) Graphic Log Sample Number Blow Count Dry Density (pcf) Moisture (%) USCS Symbol

DESCRIPTION
Logged By: MET
Sampled By: MET Type of Test
Date:

Project Name:

Drilling Company:

Drive Weight:

Elevation of Top of Hole:

Project Number:

Type of Rig:

Drop:

Hole Location:

Hole Dia:

Page:

B-4
May 8, 2024 1 of 1
Toll/23161 Mill Creek
Martini Drilling
140 pounds
+308 Feet
244006-01
Hollow Stem Auger
30 inches
See Geotechnical Map
8 inches
50/6" 113.4

EI, RDS,
COR
1 @ 0' 3-inches of asphalt concrete over
5-inches of aggregate base
@ 1.5' Clayey fine to coarse SAND, very minor
gravel; dark brown to red brown, damp,
medium dense
Total Depth = 10.5 Feet
No Ground Water Encountered
Backfilled 5/8/2024
with Native Soil and Concrete Plug
Artificial Fill, Older (Afo):
@ 0.8' Silty fine to medium SAND, very minor
gravel; dark red brown, damp, medium dense

12.1 SC/SM
2 3
86/9"
50/6"
@ 10' Becomes a very silty fine to coarse

SANDSTONE
Sespe Formation (Ts):
@ 3' Silty fine to coarse SANDSTONE; pale red
brown, damp, very dense
SM
B1
@1'-3'
113.9 8.8
110.3 9.4
CN
Project No. 244006-01 Figure B - 4 August 15, 2024

Page 1107 of 1727 ends

0 5
10 317
312
307Elevation (ft) Depth (ft) Graphic Log Sample Number Blow Count Dry Density (pcf) Moisture (%) USCS Symbol

DESCRIPTION
Logged By: MET
Sampled By: MET Type of Test
Date:

Project Name:

Drilling Company:

Drive Weight:

Elevation of Top of Hole:

Project Number:

Type of Rig:

Drop:

Hole Location:

Hole Dia:

Page:

B-5
May 8, 2024 1 of 1
Toll/23161 Mill Creek
Martini Drilling
140 pounds
+317 Feet
244006-01
Hollow Stem Auger
30 inches
See Geotechnical Map
8 inches
1 52 CN
@ 0' 8-inches of Asphalt over 5-inches of
aggregate base
Sespe Formation (Ts):
@3.5' Silty fine to medium SANDSTONE, very
minor gravel; red brown, damp, very dense
Total Depth = 10.5 Feet
No Ground Water Encountered
Backfilled 5/8/2024
with Native Soil and Concrete Plug
Artificial Fill, Older (Afo):
@ 1.1' Silty fine to medium SAND, very minor
gravel, slightly clayey; red brown, damp,
medium dense
SM
2 4
85/9"
50/6"
SM
3 50/6"
SW
@7.5' Becomes a silty fine to medium

SANDSTONE
@10' Fine to coarse SANDSTONE; red brown
to gray brown, damp, very dense
115.8 13.4
115.6 9.6
111.3 8.4
105.2 6.5
Project No. 244006-01 Figure B - 5 August 15, 2024

Page 1108 of 1727 ends

0 5
10 312
307
302Elevation (ft) Depth (ft) Graphic Log Sample Number Blow Count Dry Density (pcf) Moisture (%) USCS Symbol

DESCRIPTION
Logged By: MET
Sampled By: MET Type of Test
Date:

Project Name:

Drilling Company:

Drive Weight:

Elevation of Top of Hole:

Project Number:

Type of Rig:

Drop:

Hole Location:

Hole Dia:

Page:

B-6
May 8, 2024 1 of 1
Toll/23161 Mill Creek
Martini Drilling
140 pounds
+312 Feet
244006-01
Hollow Stem Auger
30 inches
See Geotechnical Map
8 inches
86/11"
SA, SE
1 Total Depth = 10.5 Feet
No Ground Water Encountered
Backfilled 5/8/2024
with Native Soil and Concrete Plug
Sespe Formation (Ts):
@ 2.5' Silty fine to coarse gravelly
SANDSTONE, minor fine cobbles; red brown,
damp, very dense
SW
2 3
80/8.5"
50/6"
B1
@2.5'-5'
SM
@ 5' Silty fine to coarse SANDSTONE, very
minor gravel; red brown, damp, very dense
SW
@ 0' 8-inches of asphalt concrete over
5-inches of aggregate base
Artificial Fill, Older (Afo):
@ 1.1' Silty fine to coarse gravelly SAND,
minor fine cobbles; dark red brown, damp,
medium dense
118.1 6.0
111.9 9.9
105.1 9.8
Project No. 244006-01 Figure B - 6 August 15, 2024

Page 1109 of 1727 ends

Symbol Laboratory Test
SA Sieve Analysis
H Hydrometer Anlysis
SHA Sieve & Hydrometer Analysis
-200 Percent Passing #200 Sieve
AL Atterburge Limits
MAX Maximum Density
DS Undisturbed Direct Shear
RDS Remolded Direct Shear
SE Sand Equivalent
EI Expansion Index
P Permeability
CN Consolidation
COL Collapse
UC Unconfined Compression
S Sulfate Content
pHR pH & Resistivity
COR Corrosion Suite (pH, Resistivity, Chloride, Sulfate) RV R-Value
Key to Boring Logs
Approximate Groundwater Level
Aggregate Base Approximate Seepage Location
Asphalt Concrete
GW
GP MH
SW
SP
SM
SC
CL
OH
ML
CH
PT
Gravel Sand Silt Clay
OL
Organics
Project No. 244006-01 Figure B - 7 August 15, 2024

Page 1110 of 1727 ends

Project No. 244006-01 Page C-1 August 15, 2024

APPENDIX C
Laboratory Testing Procedures and Test Results (Current Study) The laboratory testing program was directed towards providing quantitative data relating to the relevant engineering properties of the soils. Samples considered representative of site conditions were tested in general accordance with American Society for Testing and Materials (ASTM) procedure and/or California Test Methods (CTM), where applicable. The following summary is a brief outline of the test type, and the results are presented on the following pages. LGC has reviewed the laboratory test data, procedures, and results with respect to the subject site, concurs with, and accepts responsibility as geotechnical engineer of record for their work (laboratory testing).

Soil Classification: Soils were classified according to the Unified Soil Classification System (USCS) in accordance with ASTM Test Methods D2487 and D2488. This system relies on the Atterberg limits and grain size distribution of a soil. The soil classifications (or group symbol) are shown on the laboratory test data and boring logs.

Atterberg Limits: The liquid and plastic limits (“Atterberg limits”) were determined in accordance with ASTM Test Method D4318 for engineering classification of fine-grained material and presented on the following table:

Sample Location Sample Description
Liquid
Limit
(%)
Plastic
Limit
(%)
Plasticity
Index
(%)
B-1 #B1 @ 1-5’ Silty to clayey fine to medium SAND 27 15 12 Chloride Content: Chloride content was tested in accordance with CTM 422. The results are presented below:

Sample Location Sample Description
Chloride
Content
(ppm)
Potential Degree
of Chloride
Attack*
B-1 #B1 @ 1-5’ Silty to clayey fine to medium SAND 125 Negligible B-4 #B1 @ 1-3’ Clayey fine to medium SAND 140 Negligible * Extrapolation from California Test Method 532, Method for Estimating the Time to Corrosion of Reinforced Concrete Substructures and previous experience.

Page 1111 of 1727 ends

Project No. 244006-01 Page C-2 August 15, 2024
Laboratory Testing Procedures and Test Results (Current Study) (continued) Consolidation: Consolidation tests were performed on selected, relatively undisturbed ring samples (per Modified ASTM Test Method D2435). Samples (2.42 inches in diameter and 1 inch in height) were placed in a consolidometer and increasing loads were applied. The samples were allowed to consolidate under “double drainage” and total deformation for each loading step was recorded. The percent consolidation for each load step was recorded as the ratio of the amount of vertical compression to the original sample height. The consolidation pressure curves are presented on the attached figures at the end of this appendix.

Direct Shear (Remolded or Undisturbed): Direct shear tests were performed on selected remolded and/or undisturbed samples, which were soaked for a minimum of 24 hours under a surcharge equal to the applied normal force during testing. After transfer of the sample to the shear box, and reloading the sample, pore pressures set up in the sample due to the transfer were allowed to dissipate for a period of approximately 1 hour prior to application of shearing force. The samples were tested under various normal loads, a motor-driven, strain-controlled, direct-shear testing apparatus at a strain rate of less than 0.001 to 0.5 inch per minute (depending upon the soil type). The test results are presented on the following table and/or on the attached figures at the end of this appendix.

Sample
Location Sample Description
Peak/Ultimate
Friction
Angle
(degrees)
Peak/Ultimate
Apparent
Cohesion (psf)
B-1 #4 @15’ Undisturbed 29/29 278/96
B-4 #B1 @ 1-3’ Clayey fine to medium SAND (Remolded) 30/30 227/198 Expansion Index Tests: The expansion potential of selected materials was evaluated by the Expansion Index Test, UBC Standard No. 18-I-B and/or ASTM D4829. Specimens are molded under a given compactive energy to approximately the optimum moisture content and approximately 50 percent saturation or approximately 90 percent relative compaction. The prepared 1-inch thick by 4-inch diameter specimens are loaded to an equivalent 144 psf surcharge and are inundated with tap water until volumetric equilibrium is reached. The results of these tests are presented in the table below:

Sample Location Sample Description Expansion
Index
Expansion
Potential
B-1 #B1 @ 1-5’ Silty to clayey fine to medium SAND 14 Very Low B-4 #B1 @ 1-3’ Clayey fine to medium SAND 38 Low

Page 1112 of 1727 ends

Project No. 244006-01 Page C-3 August 15, 2024
Laboratory Testing Procedures and Test Results (Current Study) (continued) Maximum Dry Density Tests: The maximum dry density and optimum moisture content of typical materials were determined in accordance with ASTM Test Method D1557. The results of these tests are presented in the table below:

Sample
Location Sample Description
Maximum
Dry Density
(pcf)
Optimum
Moisture
Content (%)
B-4 #B1 @ 1-3’ Clayey fine to medium SAND 133.5 8.0
Moisture and Density Determination Tests: Moisture content (ASTM D2216) and dry density determinations (ASTM D2937) were performed on relatively undisturbed samples obtained from the test borings. The results of these tests are presented on the boring logs. Where applicable, only moisture content was determined from undisturbed or disturbed samples.

Grain Size Distribution/Sieve Analysis: Representative samples were dried, weighed, and soaked in water until individual soil particles were separated (per ASTM D421) and then washed on a No. 200 sieve. The portion retained on the No. 200 sieve was dried and then sieved on a U.S. Standard brass sieve set in accordance with ASTM D422 (CTM 202). The sieve analysis curve is presented on the attached figure at the end of this appendix. The percent passing the #200 sieve is presented on the following table:

Sample Location Sample Description Percent Passing
#200 Sieve
B-6 #B1 @2.5-5’ Silty fine to coarse gravelly SAND 26.5

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Project No. 244006-01 Page C-4 August 15, 2024
Laboratory Testing Procedures and Test Results (Current Study) (continued) Minimum Resistivity and pH Tests: Minimum resistivity and pH tests were performed in general accordance with CTM 643 and standard geochemical methods. The electrical resistivity of a soil is a measure of its resistance to the flow of electrical current. As a result of soil’s resistivity decreases corrosivity increases. The results are presented in the table below:

Sample Location Sample Description pH
Minimum
Resistivity
(ohms-cm)
Potential
Degree of
Corrosivity*
B-1 #B1 @ 1-5’
Silty to clayey fine to medium
SAND 7.82 1,700 Moderately Corrosive
B-4 #B1 @ 1-3’ Clayey fine to medium SAND 8.15 1,300 Moderately Corrosive
* NACE Corrosion Basics, 1984.

Sand Equivalent: The sand equivalent (SE) of selected samples was determined in accordance with ASTM D2419. The sand equivalent results are used to determine the applicability of material for use as backfill and to assess whether flooding or jetting is a suitable compaction method. The results are presented in the table below:

Sample Location Sample Description Sand Equivalent
Value
B-6 #B1 @2.5-5’ Silty fine to coarse gravelly SAND 14
Soluble Sulfates: The soluble sulfate contents of selected samples were determined by standard geochemical methods (CTM417). The soluble sulfate content is used to determine the appropriate cement type and maximum water-cement ratios. The test results are presented in the table below:

Sample
Location Sample Description
Sulfate
Content
(% by
weight)
Exposure Class
(Exposure
Severity)*
B-1 #B1 @ 1-5’ Silty to clayey fine to medium SAND 0.007 S0 (Not Applicable) B-4 #B1 @ 1-3’ Clayey fine to medium SAND 0.005 S0 (Not Applicable) * Per ACI 318-19 Table 19.3.2.1 (ACI, 2019).

Page 1114 of 1727 ends

Project Name:

Toll / Mill Creek 2
Client: LGC Valley, Inc.

Job No.: 244006-01
EGLAB Project No.: 24-059-009
08/24 Figure
Symbol Boring
No.

Sample
No.

Depth
(Ft.)
Soil
Type
Init. Moisture
Content (%)
B-4 1 2.5 SM 12.1
EGLAB, INC.

CONSOLIDATION
(ASTM D2435)
Init. Dry Density
(PCF)
Init. Void
Ratio
115.1 0.463
0 1
2 3
4 5
6 7
8 9
10 11
12 13
14 15
16 17
18 19
20 0.1 1 10 100
DEFORMATION (%)

COMPRESSIVE STRESS (KSF)

SATURATED
Project No. 244006-01 Figure C-1 August 15,

Page 1115 of 1727 ends

20024
Project Name:

Toll / Mill Creek 2
Client: LGC Valley, Inc.

Job No.: 244006-01
EGLAB Project No.: 24-059-009
08/24 Figure
Symbol Boring
No.

Sample
No.

Depth
(Ft.)
Soil
Type
Init. Moisture
Content (%)
B-5 1 2.5 CL/SC 13.4
EGLAB, INC.

CONSOLIDATION
(ASTM D2435)
Init. Dry Density
(PCF)
Init. Void
Ratio
118.4 0.423
0 1
2 3
4 5
6 7
8 9
10 11
12 13
14 15
16 17
18 19
20 0.1 1 10 100
DEFORMATION (%)

COMPRESSIVE STRESS (KSF)

SATURATED
Project No. 244006-01 Figure C-2 August 15,

Page 1116 of 1727 ends

20024
gd S
(pcf) (%)
1000 102.8 92
2000 103.5 92
4000 104.8 90
Boring No. Sample No. Depth (ft) Sample
Type
Soil Type Symbol Cohesion
(PSF)
Friction
Angle
B-1 4 15.0 Ring SM 227 30
198 30
Project Name:

EGLAB, INC.

Toll / Mill Creek 2

7.9 20.3 DIRECT SHEAR
Normal
Stress (psf)
Initial
Moisture (%)
Final
Moisture (%)
Client: LGC Valley, Inc.

Project No.: 244006-01
08/24 (ASTM D3080) Figure

7.9 21.8 EGLAB Project No.: , California 24-059-009

7.9 21.3
0 500
1000
1500
2000
2500
3000
3500
4000
4500
5000
0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000

SHEAR STRESS (PSF)

NORMAL PRESSURE (PSF)
Peak Ultimate
Project No. 244006-01 Figure C-3 August 15,

Page 1117 of 1727 ends

20024
Note: Sample was remolded to 90 % maximum relative density and optimum moisture Maximum Dry Density: 133.5 pcf Optimum Moisture: 8.0 %
Toll / Mill Creek 2
Client: LGC Valley, Inc.

Project No.: 244006-01
500 EGLAB Project No.: 24-059-009
1000
2000
Normal
Stress
(psf)
B-4 B1 1.0-3.0 SC
EGLAB, INC.

19.0 Cohesion
(PSF) Boring No.

Sample
No.

Symbol
96 Bulk
Depth (ft)
Figure
Initial
Moisture
(%)
Final
Moisture
(%)

18.1 7.8 19.5

7.8 7.8
29 (ASTM D3080)
Sample
Type
08/24
278
Friction
Angle
29 DIRECT SHEAR
Project Address:

Soil Type
0 500
1000
1500
2000
2500
3000
0 500 1000 1500 2000 2500 3000

SHEAR STRESS (PSF)

NORMAL PRESSURE (PSF)
Peak
Ultimate
Project No. 244006-01 Figure C-4 August 15,

Page 1118 of 1727 ends

20024

SYMBOL BORING
NO.

SAMPLE
NO.

DEPTH
(FT)
SAMPLE
TYPE
SOIL
TYPE
LIQUID
LIMIT
B-6 B1 2.5-5.0 Bulk SC N/A
Gravel: 23.3%
Sand: 50.2%
Fine: 26.5%
Client Job No.:

Client Name:

EGLAB Project No.:

GRAIN SIZE

DISTRIBUTION CURVE
08/07/24 (ASTM D422) FIGURE
24-059-009
EGLAB, INC.

LGC Valley, Inc.
244006-01

PLASTICITY
INDEX
N/A
Project Name:

Toll / Mill Creek 2
0 10
20 30
40 50
60 70
80 90
100
100 10 1 0.1 0.01

PERCENT FINER BY WEIGHT
GRAIN SIZE (mm)
U.S STANDARD SIEVE OPENING U.S. STANDARD SIEVE NUMBER HYDROMETER

GRAVEL SAND

COARSE FINE COAR MEDIUM FINE

SILT OR CLAY
3" 1.5" 1" 3/4" 1/2" 3/8" #4 #10 #20 #40 #60 #100 #200
Project No. 244006-01 Figure C-5 August 15,

Page 1119 of 1727 ends

20024
Boring No: B-4
Sample: B1
(ASTM D1557) Date :

Client Name:
24-059-009
Job No.:

Maximum Dry Density = 133.5
Toll / Mill Creek 2
Figure
LGC Valley, Inc.

Modified Proctor
EGLAB, INC.
pcf
Optimum Moisture Content = 8.0 %
Method "A"
Aug-24
244006-01
Project Name:

Description : Clayey sand (SC), reddish brown,
trace of gravel
Depth : 1.0-3.0 feet
EGLAB Project No.:
90 100
110
120
130
140
150
0 5 10 15 20 25 30 35
Dry Density, pcf
Moisture Content %
Gs=2.95
Gs=2.85
Gs=2.75
Gs=2.65
Project No. 244006-01 Figure C-6 August 15,

Page 1120 of 1727 ends

20024
Project No. 244006-01 Page D-1 August 15, 2024

APPENDIX D
Previous Geotechnical Borings Logs (by Others)

Page 1121 of 1727 ends

~ ;' .
•
•
•
•
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•
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so· n.:;L
~
. .
.
sr,• p =''·J
~ Dre\1~/reddlsh brown CU11Y.&Y Sl\llll
Br.;·..,ll/tliddish brcl/n SI\IIOV Sll.T,
132/50/lB.I P s•
Liqht ~~ddJ &h bro!ltl 571.'1'\' F:r!I£-'HtDIUI! 511!10 Droun/ruddhh bro~m SII-S't(it;r
130/M/:\.4) 0 25 I .
110 GROUt:oiiATER ·
UO CAVING.
~l:lllll
Q - Undbturb~d· core G~pho .'
(\Sand/\ silt/~ cl'a~•) @ :sample. dnptl:t
ii.S,;C• - llrtifLQd soi1 c1aaUt!c.iUon 5,\filtem Group Sl'lOhoi.

DrY \ J.lointUrtl p.,nn!tt• l!!:r U • .G.c.
sc
tiL
ro l2S
15 ill
111
20 . 112
112
10 l.lS
121
9 ill
1 lti
tiLl: No, •BS,.l07B9
j\, V. \li,',!\W.'liliU co,, 1liC,
Project No. 244006-01 Figure D - 1 August 15, 2024

Page 1122 of 1727 ends

•
•
•
•
•
•
•
•
•
••
. · .. / :]
l:""""!"--------~-----'!""""-----....... -------------1--·· _.....,._.., Soil claosiflcAtion
tiTtTUMt.c . Bro•'ll/reddbh bro\m St.IID\' SlLT,
~y ll2/SC/lBI @ IJ!
t.lqht qrayish brown SMlD,STOUt
Ydlowish br""''ll S]tTSTOII£/SIIIIOSTOIIt
UO GROUUDithTtil
liD 'CAVliiC
\ lloJatllra
11 12
10 l.l
12 10
6 '
io
B
11 . .
cry
Danoltt• p.:C
ll!i
112
1U
119
102
. 102.
114
U.l
115
116
.l!.s.c.
sc
,£it£ llo. · BS-10789
,II. v. Lt.,.'>Wi'n:A, t. co. I liiC •
Project No. 244006-01 Figure D - 2 August 15, 2024

Page 1123 of 1727 ends

LGC Valley, Inc.

General Earthwork and Grading Specifications

Page 1 of 5 ends

APPENDIX E
General Earthwork and Grading Specifications for Rough Grading

1.0 General

1.1 Intent: These General Earthwork and Grading Specifications are for the grading and earthwork shown on the approved grading plan(s) and/or indicated in the geotechnical report(s). These Specifications are a part of the recommendations contained in the geotechnical report(s). In case of conflict, the specific recommendations in the geotechnical report shall supersede these more general Specifications. Observations of the earthwork by the project Geotechnical Consultant during the course of grading may result in new or revised recommendations that could supersede these specifications or the recommendations in the geotechnical report(s).

1.2 The Geotechnical Consultant of Record: Prior to commencement of work, the owner shall employ a qualified Geotechnical Consultant of Record (Geotechnical Consultant).

The Geotechnical Consultant shall be responsible for reviewing the approved geotechnical report(s) and accepting the adequacy of the preliminary geotechnical findings, conclusions, and recommendations prior to the commencement of the grading.

Prior to commencement of grading, the Geotechnical Consultant shall review the "work plan" prepared by the Earthwork Contractor (Contractor) and schedule sufficient personnel to perform the appropriate level of observation, mapping, and compaction testing.

During the grading and earthwork operations, the Geotechnical Consultant shall observe, map, and document the subsurface exposures to verify the geotechnical design assumptions. If the observed conditions are found to be significantly different than the interpreted assumptions during the design phase, the Geotechnical Consultant shall inform the owner, recommend appropriate changes in design to accommodate the observed conditions, and notify the review agency where required.

The Geotechnical Consultant shall observe the moisture-conditioning and processing of the subgrade and fill materials and perform relative compaction testing of fill to confirm that the attained level of compaction is being accomplished as specified. The Geotechnical Consultant shall provide the test results to the owner and the Contractor on a routine and frequent basis.

1.3 The Earthwork Contractor: The Earthwork Contractor (Contractor) shall be qualified, experienced, and knowledgeable in earthwork logistics, preparation, and processing of ground to receive fill, moisture-conditioning and processing of fill, and compacting fill.

The Contractor shall review and accept the plans, geotechnical report(s), and these Specifications prior to commencement of grading. The Contractor shall be solely responsible for performing the grading in accordance with the project plans and specifications. The Contractor shall prepare and submit to the owner and the Geotechnical Consultant a work plan that indicates the sequence of earthwork grading,

Page 1124 of 1727 ends

LGC Valley, Inc.

General Earthwork and Grading Specifications

Page 2 of 5 ends

the number of “equipment” of work and the estimated quantities of daily earthwork contemplated for the site prior to commencement of grading. The Contractor shall inform the owner and the Geotechnical Consultant of changes in work schedules and updates to the work plan at least 24 hours in advance of such changes so that appropriate personnel will be available for observation and testing. The Contractor shall not assume that the Geotechnical Consultant is aware of all grading operations.

The Contractor shall have the sole responsibility to provide adequate equipment and methods to accomplish the earthwork in accordance with the applicable grading codes and agency ordinances, these Specifications, and the recommendations in the approved geotechnical report(s) and grading plan(s). If, in the opinion of the Geotechnical Consultant, unsatisfactory conditions, such as unsuitable soil, improper moisture condition, inadequate compaction, insufficient buttress key size, adverse weather, etc., are resulting in a quality of work less than required in these specifications, the Geotechnical Consultant shall reject the work and may recommend to the owner that construction be stopped until the conditions are rectified. It is the contractor’s sole responsibility to provide proper fill compaction.

2.0 Preparation of Areas to be Filled

2.1 Clearing and Grubbing: Vegetation, such as brush, grass, roots, and other deleterious material shall be sufficiently removed and properly disposed of in a method acceptable to the owner, governing agencies, and the Geotechnical Consultant.

The Geotechnical Consultant shall evaluate the extent of these removals depending on specific site conditions. Earth fill material shall not contain more than 1 percent of organic materials (by volume). No fill lift shall contain more than 10 percent organic matter. Nesting of organic materials shall not be allowed.

If potentially hazardous materials are encountered, the Contractor shall stop work in the affected area, and a hazardous material specialist shall be informed immediately for proper evaluation and handling of these materials prior to continuing to work in that area.

As presently defined by the State of California, most refined petroleum products (gasoline, diesel fuel, motor oil, grease, coolant, etc.) have chemical constituents that are considered to be hazardous waste. As such, the indiscriminate dumping or spillage of these fluids onto the ground may constitute a misdemeanor, punishable by fines and/or imprisonment, and shall not be allowed. The contractor is responsible for all hazardous waste relating to his work. The Geotechnical Consultant does not have expertise in this area. If hazardous waste is a concern, then the Client should acquire the services of a qualified environmental assessor.

2.2 Processing: Existing ground that has been declared satisfactory for support of fill by the Geotechnical Consultant shall be scarified to a minimum depth of 6 inches. Existing ground that is not satisfactory shall be overexcavated as specified in the following section. Scarification shall continue until soils are broken down and free from oversize

Page 1125 of 1727 ends

LGC Valley, Inc.

General Earthwork and Grading Specifications

Page 3 of 5 ends

material and the working surface is reasonably uniform, flat, and free from uneven features that would inhibit uniform compaction.

2.3 Overexcavation: In addition to removals and overexcavations recommended in the approved geotechnical report(s) and the grading plan, soft, loose, dry, saturated, spongy, organic-rich, highly fractured, or otherwise unsuitable ground shall be overexcavated to competent ground as evaluated by the Geotechnical Consultant during grading.

2.4 Benching: Where fills are to be placed on ground with slopes steeper than 5:1 (horizontal to vertical units), the ground shall be stepped or benched. Please see the Standard Details for a graphic illustration. The lowest bench or key shall be a minimum of 15 feet wide and at least 2 feet deep, into competent material as evaluated by the Geotechnical Consultant. Other benches shall be excavated a minimum height of 4 feet into competent material or as otherwise recommended by the Geotechnical Consultant.

Fill placed on ground sloping flatter than 5:1 shall also be benched or otherwise overexcavated to provide a flat subgrade for the fill.

2.5 Evaluation/Acceptance of Fill Areas: All areas to receive fill, including removal and processed areas, key bottoms, and benches, shall be observed, mapped, elevations recorded, and/or tested prior to being accepted by the Geotechnical Consultant as suitable to receive fill. The Contractor shall obtain a written acceptance from the Geotechnical Consultant prior to fill placement. A licensed surveyor shall provide the survey control for determining elevations of processed areas, keys, and benches.

3.0 Fill Material

3.1 General: Material to be used as fill shall be essentially free from organic matter and other deleterious substances evaluated and accepted by the Geotechnical Consultant prior to placement. Soils of poor quality, such as those with unacceptable gradation, high expansion potential, or low strength shall be placed in areas acceptable to the Geotechnical Consultant or mixed with other soils to achieve satisfactory fill material.

3.2 Oversize: Oversize material defined as rock, or other irreducible material with a maximum dimension greater than 8 inches, shall not be buried or placed in fill unless location, materials, and placement methods are specifically accepted by the Geotechnical Consultant. Placement operations shall be such that nesting of oversized material does not occur and such that oversized material is completely surrounded by compacted or densified fill. Oversize material shall not be placed within 10 vertical feet of finish grade or within 2 feet of future utilities or underground construction.

3.3 Import: If importing of fill material is required for grading, proposed import material shall meet the requirements of Section 3.1. The potential import source shall be given to the Geotechnical Consultant at least 48 hours (2 working days) before importing begins so that its suitability can be determined, and appropriate tests performed.

Page 1126 of 1727 ends

LGC Valley, Inc.

General Earthwork and Grading Specifications

Page 4 of 5 ends

4.0 Fill Placement and Compaction

4.1 Fill Layers: Approved fill material shall be placed in areas prepared to receive fill (per Section 3.0) in near-horizontal layers not exceeding 8 inches in loose thickness. The Geotechnical Consultant may accept thicker layers if testing indicates the grading procedures can adequately compact the thicker layers. Each layer shall be spread evenly and mixed thoroughly to attain relative uniformity of material and moisture throughout.

4.2 Fill Moisture Conditioning: Fill soils shall be watered, dried back, blended, and/or mixed, as necessary to attain a relatively uniform moisture content at or slightly over optimum. Maximum density and optimum soil moisture content tests shall be performed in accordance with the American Society of Testing and Materials (ASTM Test Method D1557-91).

4.3 Compaction of Fill: After each layer has been moisture conditioned, mixed, and evenly spread, it shall be uniformly compacted to not less than 90 percent of maximum dry density (ASTM Test Method D1557-91). Compaction equipment shall be adequately sized and be either specifically designed for soil compaction or of proven reliability to efficiently achieve the specified level of compaction with uniformity.

4.4 Compaction of Fill Slopes: In addition to normal compaction procedures specified above, compaction of slopes shall be accomplished by backrolling of slopes with sheeps-foot rollers at increments of 3 to 4 feet in fill elevation, or by other methods producing satisfactory results acceptable to the Geotechnical Consultant. Upon completion of grading, relative compaction of the fill, out to the slope face, shall be at least 90 percent of maximum density per ASTM Test Method D1557-91.

4.5 Compaction Testing: Field tests for moisture content and relative compaction of the fill soils shall be performed by the Geotechnical Consultant. Location and frequency of tests shall be at the Consultant's discretion based on field conditions encountered.

Compaction test locations will not necessarily be selected on a random basis. Test locations shall be selected to verify adequacy of compaction levels in areas that are judged to be prone to inadequate compaction (such as close to slope faces and at the fill/bedrock benches).

4.6 Frequency of Compaction Testing: Tests shall be taken at intervals not exceeding 2 feet in vertical rise and/or 1,000 cubic yards of compacted fill soils embankment. In addition, as a guideline, at least one test shall be taken on slope faces for each 5,000 square feet of slope face and/or each 10 feet of vertical height of slope. The Contractor shall assure that fill construction is such that the testing schedule can be accomplished by the Geotechnical Consultant. The Contractor shall stop or slow down the earthwork construction if these minimum standards are not met.

4.7 Compaction Test Locations: The Geotechnical Consultant shall document the approximate elevation and horizontal coordinates of each test location. The Contractor shall coordinate with the project surveyor to assure that sufficient grade stakes are established so that the Geotechnical Consultant can determine the test locations with

Page 1127 of 1727 ends

LGC Valley, Inc.

General Earthwork and Grading Specifications

Page 5 of 5 ends

sufficient accuracy. At a minimum, two grade stakes within a horizontal distance of 100 feet and vertically less than 5 feet apart from potential test locations shall be provided.

5.0 Subdrain Installation
Subdrain systems shall be installed in accordance with the approved geotechnical report(s), the grading plan, and the Standard Details. The Geotechnical Consultant may recommend additional subdrains and/or changes in subdrain extent, location, grade, or material depending on conditions encountered during grading. All subdrains shall be surveyed by a land surveyor/civil engineer for line and grade after installation and prior to burial. Sufficient time should be allowed by the Contractor for these surveys.

6.0 Excavation
Excavations, as well as over-excavation for remedial purposes, shall be evaluated by the Geotechnical Consultant during grading. Remedial removal depths shown on geotechnical plans are estimates only. The actual extent of removal shall be determined by the Geotechnical Consultant based on the field evaluation of exposed conditions during grading. Where fill-over-cut slopes are to be graded, the cut portion of the slope shall be made, evaluated, and accepted by the Geotechnical Consultant prior to placement of materials for construction of the fill portion of the slope, unless otherwise recommended by the Geotechnical Consultant.

7.0 Trench Backfills

7.1 The Contractor shall follow all OHSA and Cal/OSHA requirements for safety of trench excavations.

7.2 All bedding and backfill of utility trenches shall be done in accordance with the applicable provisions of Standard Specifications of Public Works Construction.

Bedding material shall have a Sand Equivalent greater than 30 (SE>30). The bedding shall be placed to 1 foot over the top of the conduit and densified by jetting. Backfill shall be placed and densified to a minimum of 90 percent of maximum from 1 foot above the top of the conduit to the surface.

7.3 The jetting of the bedding around the conduits shall be observed by the Geotechnical Consultant.

7.4 The Geotechnical Consultant shall test the trench backfill for relative compaction. At least one test should be made for every 300 feet of trench and 2 feet of fill.

7.5 Lift thickness of trench backfill shall not exceed those allowed in the Standard Specifications of Public Works Construction unless the Contractor can demonstrate to the Geotechnical Consultant that the fill lift can be compacted to the minimum relative compaction by his alternative equipment and method.

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Project No. 244006-01 Figure E - 1 August 15, 2024

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Project No. 244006-01 Figure E - 2 August 15, 2024

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Project No. 244006-01 Figure E - 3 August 15, 2024

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Project No. 244006-01 Figure E - 4 August 15, 2024

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Toll West Coast, LLC
350 Commerce, Suite 200, Irvine, CA
Office: (714) 347-1300

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July 25, 2025
Mr. Evan Carey
Fire Prevention Analyst
Orange County Fire Authority
1 Fire Authority Road
Irvine, CA 92602
Subject: Response to Service Code: PR105 Site Development Review for SR25002714/ Dear Mr. Evan Carey:

On June 24, 2025, Toll West Coast LLC (“Toll Brothers”), received a site development review for OCFA Service Request SR 25002714 for our proposed development at 23161 Mill Creek Drive.

It was noted that OCFA has reviewed the project, and the initial assessment has not returned and significant concerns. The review included the conditions of approval listed below with our responses.

CONDITIONS OF APPROVAL:

Plan Submittal: The applicant or responsible party shall submit the plan(s) listed below to the Orange County Fire Authority for review. Approval shall be obtained on each plan prior to the event specified.

Prior to OCFA clearance of a final map or issuance of a precise grading permit or a building permit, if a grading permit is not required:
 fire master plan (service code PR145)
Response: Noted.

Prior to issuance of a precise grading permit or a building permit, if a grading permit is not required:
 gates (service code PR180)
Response: Noted.

Prior to the issuance of a building permit:
 Underground piping for private hydrants and fire sprinkler systems if present (service code PR470-PR475)
Response: An Underground Fire Protection Plan should not be required since all on-site hydrants will be public, not private, and all units will be protected by an NFPA 13-D system.

 fire sprinkler system (service codes PR400-PR465)
Response: Noted.

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Toll West Coast, LLC
350 Commerce, Suite 200, Irvine, CA
Office: (714) 347-1300

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Temporary/Final Occupancy Inspections:

Prior to issuance of temporary or final certificate of occupancy, all OCFA inspections shall be completed to the satisfaction of the OCFA inspector and be in substantial compliance with codes and standards applicable to the project and commensurate with the type of occupancy (temporary or final) requested. Inspections shall be scheduled at least five days in advance by calling OCFA Inspection Scheduling at 714-573-6150.

Response: Noted.

Lumber-drop Inspection:

After installation of required fire access roadways and hydrants, the applicant shall receive clearance from the OCFA prior to bringing combustible building materials on-site. Call OCFA Inspection Scheduling at 714-573-6150 with the Service Request number of the approved fire master plan at least five days in advance to schedule the lumber drop inspection.

Response: Noted.

We look forward to working further with you on this submittal. Should you have any questions or need additional information, please contact me at (949) 400-7214.

Sincerely,
Aylene Chu
Director of Land Entitlements
Toll West Coast, LLC
cc:

Salvador Avila, Toll West Coast LLC
Jason Certilman, Toll West Coast LLC
Peter Kim, Toll West Coast LLC
Alicia Guerra, Buchalter, PC
Braeden Mansouri, Buchalter, PC

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LAGUNA HILLS HILLSIDE PLAZA

REDEVELOPMENT PROJECT
Net Fiscal Impact Analysis
Prepared For: Toll Brothers, Inc.

January 2025
Prepared By:
1601 N. Sepulveda Blvd. #382
Manhattan Beach, CA 90266
www.kosmont.com

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Toll Brothers – Laguna Hills Hillside Plaza
Net Fiscal Impact Analysis
January 2025

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Table of Contents

3.0 Executive Summary ........................................................................................................3

3.0 Project Description .........................................................................................................6

3.0 Fiscal Impacts..................................................................................................................8

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Toll Brothers – Laguna Hills Hillside Plaza
Net Fiscal Impact Analysis
January 2025

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Executive Summary
Toll Brothers (“Client” / “Developer”) is currently pursuing entitlements for the development of a 36-unit duplex residential project (“Project”) on an approximately 2.43-acre property (APN 588- 142-07) (“Site”) located at 23161 Mill Creek Drive in the City of Laguna Hills (“City”). In order to assist the City’s evaluation of the proposed Project, Client requested that Kosmont Companies (“Kosmont”) prepare a Fiscal Impact Analysis (“Analysis”) to estimate the projected net fiscal impacts of the Project to the City. Kosmont’s Analysis also estimates the approximate impact of the existing office properties located on the Site, which would be redeveloped.

Kosmont’s Analysis demonstrates that the redevelopment of the Project has a potential financial benefit to the City General Fund, driving ~$58,500 in annual fiscal revenues and ~$48,700 in annual fiscal costs, resulting in an annual net fiscal benefit of approximately $9,800.

Annual Fiscal Impact
The Project is estimated to generate an annual fiscal revenue of approximately $58,500 at full buildout in 2024 dollars, largely due to the significant increase in property value – the existing office properties have an estimated value of $15,000,000, compared to the Project’s estimated value of $57,120,000 at completion.

The Project is expected to result in approximately $48,700 in General Fund expenditures, yielding a positive annual net fiscal impact of $9,800. The existing office properties are estimated to generate $18,500 in annual fiscal revenues and result in an estimated $24,400 in General Fund expenditures, yielding a current negative annual fiscal impact of ($5,900). In this regard, the Project compares favorably to the existing land use.

Fiscal revenues and expenses are summarized in the table on the following page.

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Net Fiscal Impact Analysis
January 2025

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Table 1.1: Summary of Annual Fiscal Impact
Source: Kosmont Companies, Laguna Hills, Toll Brothers

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Net Fiscal Impact Analysis
January 2025

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Other Benefits
In addition to General Fund revenues, the Project will provide indirect benefits to City, County, the Saddleback Valley Unified School District (“School District”), and the Moulton Niguel Water District (“Water District”).
• Local businesses will benefit from $1.85 million in increased spending from new residents, with an estimated $424,000 of taxable spending captured by businesses in the City of Laguna Hills;
• The City is estimated to receive one-time permit and plan check fees of ~$13,700 per unit, or ~$470,700;
• The School District is estimated to receive one-time developer school impact fees of ~$9,660 per unit, or ~$347,800.
• The Water District is estimated to receive one-time developer impact fees of ~$4,300 per unit, or ~$155,100.
• The School District is estimated to receive 47.73% of the increased basic 1% property tax levy, yielding an estimated $259,000 per year.
• The Orange County Fire Authority will receive 11.83% of the increased basic 1% property tax levy, yielding an estimated $64,200 per year.

As discussed above, the Project has indirect and direct benefits to the local community and City General Fund.

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Net Fiscal Impact Analysis
January 2025

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2.0 Project Description
The Project is planned to be developed on the ~2.43 acre Site at 23161 Mill Creek Drive, located north of the intersection of Mill Creek Drive and Ridge Route Drive in Laguna Hills, California. The Project is adjacent to small commercial / office buildings and is also proximate to residential neighborhoods.

Figure 2.1 Aerial Photo of Site and Immediate Neighborhood

2.2 Project Summary
The ~2.43-acre Site is currently occupied with a Class B office building (also known as Hillside Plaza) totaling ~48,800 SF (estimated current occupancy of 60%) built in 1987, as well as surface parking lots. The proposed Project will redevelop the site with 36 duplex housing units (with 2 of those units being affordable housing units). Figure 2.2 on following page shows the conceptual site plan.

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Toll Brothers – Laguna Hills Hillside Plaza
Net Fiscal Impact Analysis
January 2025

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Figure 2.2 Site Plan
Source: Toll Brothers

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Net Fiscal Impact Analysis
January 2025

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3.0 Fiscal Impacts
The Analysis evaluates the stabilized annual fiscal revenues expected for the City’s General Fund for the proposed Project at completion. Fiscal revenue estimates were derived from estimating the various taxes including property taxes (secured and unsecured), property transfer taxes, indirect sales taxes, and other taxes and revenue. The Analysis is based on information provided by the Client, City, County Property Tax Auditor-Controller’s Office, California Department of Finance (“DOF”), California Board of Equalization (“BOE”), CoStar, and ESRI.

3.1 General Assumptions
Given the uncertainty of actual development timing and future inflation rates for revenues and expenses, Kosmont has focused the fiscal analysis on annual impacts at stabilized occupancy in 2024 dollars.

3.2 Fiscal Revenue Analysis

3.2.1 Property Tax
Secured property tax revenues are estimated based on the anticipated assessed value of the Project upon full build-out and the applicable property tax rate for the City. The Site is located in County tax rate area (“TRA”) #31096. The City’s General Fund receives approximately 3.25% of the annual 1.0% secured property tax general levy placed by the County on the assessed value of the property ($0.03245131944 of each $1.00 of secured property tax revenue) within this TRA.

Additionally, unsecured property taxes are collected based on the assessed value of real property not affixed to the underlying land, such as business fixtures, and some types of vehicles. The rate of taxation and apportionment is generally the same as for secured property taxes. For the purposes of this Analysis, the assessed value of unsecured property associated with the Project is estimated to be 0.0% of the assessed value of secured property for the Project, and the assessed value of unsecured property associated with the existing office development is estimated to be 5.0% of the assessed value of secured property.

Based on an estimated average sale price of ~$1,680,000 per unit (and assuming an assessed value of $0 for the two affordable units), the Project is expected to yield an assessed value of ~$57,120,000 at completion. The Project is estimated to generate $17,600 in property taxes to the City. The current office property, when valued based on the transacted price of $15,000,000, is estimated to generate $4,900 in property taxes to the City.

Additionally, the Orange County Fire Authority General Fund receives 11.83% of the annual 1.0% secured property tax general levy ($0.11834584895 of each $1.00 of secured property tax revenue) to fund fire services, and the Saddleback Valley Unified School District General Fund

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Toll Brothers – Laguna Hills Hillside Plaza
Net Fiscal Impact Analysis
January 2025

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The analyses, projections, assumptions and any examples presented herein are for illustrative purposes and are not a guarantee of actual and/or future results. Actual results may differ from those expressed in this analysis, as results are difficult to predict as a function of market conditions, natural disasters, pandemics, significant economic impacts, legislation and administrative actions. receives 47.73% of the annual 1.0% secured property tax general levy ($0.47725744067 of each $1.00 of secured property tax revenue) to fund educational services.

Exhibit 3.2.1 Property Taxes
Source: Toll Brothers, County Assessor, Kosmont Companies

3.2.2 Taxes in Lieu of VLF
Prior to 2004, a percentage of State of California motor vehicle license fee (“VLF”) was distributed to cities. In 2005, the State instituted a revenue swap, guaranteeing that municipalities within California receive a distribution equal to the VLF collected, plus a percentage equal to the annual increase in assessed value. Property Tax In-Lieu of VLF resulting from the Project is estimated based on the incremental amount of assessed value the development will add to the City, thereby increasing the City’s apportionment or estimated VLF revenues of $22,500 in 2024 dollars. The current office property is estimated to generate $5,900 of VLF revenues in 2024 dollars.

Exhibit 3.2.2 Taxes in Lieu of VLF
Source: Toll Brothers, Kosmont Companies, City Budget and ACFR

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Net Fiscal Impact Analysis
January 2025

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3.2.3 Real Property Transfer Tax
Property transfer tax revenue is estimated based on the expected average rate of turnover of ownership of 15.0% for residential product (on average, each property selling once every seven years) and 5.0% for commercial product (on average, approximately once every 20 years), estimated $2024 values, and the City’s property transfer tax of 0.055% of gross sales price. The Project is estimated to generate an expected annual average of $4,500 in property transfer taxes to the City. The current office property, when valued based on the sale price of $15,000,000, is estimated to generate $400 in property transfer taxes to the City.

Exhibit 3.2.3: Property Transfer Tax
Source: Toll Brothers, Kosmont Companies, City Budget and ACFR

3.2.4 Sales Tax (Off-Site / Indirect)
The Project and the current office property are not expected to generate any direct / on-site sales tax.

Off-site / indirect sales tax revenue projections are estimated based on the taxable sales generated by the spending of Project residents, businesses and employees within the area.

Employee spending is based on average household incomes and BLS Consumer Expenditure Survey data, which provides spending habits of consumers based on household income, as well as resident consumption patterns and retail sales patterns within the City. Capture rates for spending by employees and residents within the City are approximated by Kosmont based on an evaluation of retail amenities within the local trade area.

Annual Use Tax is given to each City based fair share allocation of online sales taxes through County Pools, averaging ~15% of the local sales taxes generated.

In order to estimate annual spending potential, Kosmont examined the average household earnings for the City residents (i.e. $172,700), as well as for the Project’s Census Tract ($140,600)

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Net Fiscal Impact Analysis
January 2025

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The analyses, projections, assumptions and any examples presented herein are for illustrative purposes and are not a guarantee of actual and/or future results. Actual results may differ from those expressed in this analysis, as results are difficult to predict as a function of market conditions, natural disasters, pandemics, significant economic impacts, legislation and administrative actions. and assumed a mid-range household income value of $155,000 for the Project’s market-rate housing units and $70,000 for the Project’s affordable housing units, yielding a weighted average of ~$150,000.

At stabilized occupancy, the total annual resident taxable retail spending is estimated at an average of $1.41 million. Based on the Project’s location near Irvine, Laguna Woods, and Lake Forest, the Analysis assumes 30% Citywide capture rate for annual taxable spending.

Exhibit 4.2.4 shows the annual sales tax to the General Fund estimated at $4,900 per year as shown below. The current office property is estimated to generate $2,800 of off-site sales tax revenues in 2024 dollars (assuming office employee salaries of $95,000, 98 employees at the project, and a city capture rate of 10%).

Exhibit 3.2.4: Sales Tax (Off-Site/Indirect)
Source: ESRI and Kosmont Companies

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Net Fiscal Impact Analysis
January 2025

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3.2.5 Multiplier Based Revenues
In addition to the specific revenues identified above, a number of other City revenues are identified and evaluated generally based on a per resident, or per equivalent resident metric. These revenue sources include franchise fees, fines / forfeitures, charges for services, other taxes and fees, and miscellaneous revenue. These revenues are estimated based on historic City revenue metrics applied to the residents or equivalent residents attributed to the Project. These multiplier revenues to the General Fund generated by the Project are estimated at $9,000 per year as shown below.

The current office property is estimated to generate $4,500 of multiplier tax revenues in 2024 dollars
Exhibit 3.2.5 Multiplier-based Revenues
Source: Kosmont Companies, City Budget and ACFR, ESRI, CA Dept of Finance

3.3 Fiscal Expenditure Analysis
General Fund Expenditures such as public safety, public works, community services, and community development are estimated on a per capita basis using the City’s Fiscal Year 2024- 2025 Adopted Budget, and the 30,300 resident population and 16,800 local employees (per Census data / City ACFR) within the City, yielding a resident-equivalent service population of 38,800 as shown in Exhibit 3.3.1 below.

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Net Fiscal Impact Analysis
January 2025

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Exhibit 3.3.1 Citywide Service Population
Source: Kosmont Companies, City Budget and ACFR, CA Dept of Finance At stabilized occupancy assuming 2.72 average residents per housing unit (the Citywide average) and with 100% occupancy, there will be 98 residents at the Project. The existing office development is assumed to have an employee count of 98 people (60% occupancy, 300 SF per employee), which are weighted at 50% to yield a population of 49 equivalent residents. Kosmont reviewed each department to estimate the fixed and variable components of the 2023/24 budget in order to estimate the per capita cost impact of the new residents (as well as a comparison with the cost impact of employees at the current office building).

Total expenses related to the Project and the current office development are estimated based on the number of residents or equivalent residents attributed to each. These multiplier expenses to the General Fund generated by the Project are estimated at $48,700 per year as shown below.

The current office property is estimated to generate $24,400 of multiplier expenses in 2024 dollars Exhibit 3.3.2 Multiplier Based Expenses
Source: Kosmont Companies, City Budget and ACFR, ESRI, CA Dept of Finance

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Net Fiscal Impact Analysis
January 2025

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3.4 Annual Net Fiscal Impact
Based on the fiscal model discussed herein, the Project is estimated to generate approximately $58,500 in annual fiscal revenues (~$1,625 per unit) to the City’s General Fund, and drive approximately $48,700 in annual fiscal expenses (~$1,350 per unit). As a result, the Project is expected to generate net positive revenues to the City’s General Fund of approximately $9,800 per year.

The existing office development is estimated to generate approximately $18,500 in annual fiscal revenues to the City’s General Fund, and drive approximately $24,400 in annual fiscal expenses.

As a result, the existing office development generates net negative revenues to the City’s General Fund of ($5,900).

For reference, and as shown in Table 3.3 below, primary revenue drivers include property taxes and off-site sales tax, while primary expenses include public safety, public works, and community services.

Exhibit 3.4.1 Fiscal Benefit Comparison
Source: Toll Brothers, Laguna Hills, Kosmont Companies

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Phase I Cultural Resources Report
23161 Mill Creek Project, City of Laguna Hills,
Orange County, California
Prepared For:

City of Laguna Hills
24035 El Toro Road
Laguna Hills, California 92653
Prepared By:
2061 N. Los Robles Avenue, Suite 205
Pasadena, California 91104
Authors: Samantha Jovanovic, MS, MA, Kevin Hunt, BA, and Samantha Murray, MA, RPA September 2025

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Phase I Cultural Resources Report
23161 Mill Creek Project, Laguna Hills, Orange County
i September 2025
Table of Contents
Executive Summary ........................................................................................................................................................1 1 Introduction .............................................................................................................................................................2

1.1 Project Location...........................................................................................................................................2

1.2 Project Description .....................................................................................................................................5

1.3 Project Study Area ......................................................................................................................................6

1.4 Regulatory Setting......................................................................................................................................6 2 Environmental Setting....................................................................................................................................... 11 3 Cultural Setting.................................................................................................................................................... 12

3.1 Prehistoric Context.................................................................................................................................. 12

3.2 Ethnographic Context............................................................................................................................. 13

3.3 Historic Context........................................................................................................................................ 15 4 Background Research........................................................................................................................................ 19

4.1 CHRIS Records Search............................................................................................................................ 19

4.2 Native American Scoping...................................................................................................................... 22

4.3 Historical Topographic Map and Aerial Photograph Review.................................................. 24 5 Archaeological Survey....................................................................................................................................... 26

5.1 Methods and Results .............................................................................................................................. 26 6 Findings and Recommendations................................................................................................................... 31

6.1 Findings........................................................................................................................................................ 31

6.2 Standard Regulatory Requirements.................................................................................................. 31 7 Bibliography.......................................................................................................................................................... 32 Appendix A: Records Search Results Summary............................................................................................... 36 Appendix B: Native American Scoping............................................................................................................... 37 Appendix C: Preparer’s Qualifications................................................................................................................. 38

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Phase I Cultural Resources Report
23161 Mill Creek Project, Laguna Hills, Orange County
ii September 2025
Figures
Figure 1. Project Location ............................................................................................................................................3 Figure 2. Project Site Detail .........................................................................................................................................4 Tables
Table 1. Previous Cultural Resources Investigations Within 0.5-Mile of the Project Site ................. 19 Table 2. Summary of Native American Outreach............................................................................................. 23 Appendices
Appendix A: Records Search Results Summary
Appendix B: Native American Scoping
Appendix C: Preparer’s Qualifications

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Phase I Cultural Resources Report
23161 Mill Creek Project, Laguna Hills, Orange County
1 September 2025
Executive Summary
South Environmental was retained to complete a Phase I cultural resources assessment for the 23161 Mill Creek Project (proposed project, project site) located in the City of Laguna Hills, Orange County, California. This study includes the results of a California Historical Resources Information Center (CHRIS) records search of the project site and a one-half-mile radius; a California Native American Heritage Commission (NAHC) Sacred Lands File search and informational letters to local tribes; and an intensive-level pedestrian survey of the project site by a qualified archaeologist. This study was completed in compliance with the California Environmental Quality Act (CEQA), including Public Resources Code (PRC) Section 5024.1, Title 14 California Code of Regulations (CCR) Section 15064.5 of the CEQA Guidelines, and PRC Sections 21083.2 and 21084.1.

No cultural resources were identified within the project site as a result of the CHRIS records search, NAHC Sacred Lands File search, Native American coordination, and pedestrian survey by a qualified archaeologist. The entire project site has been disturbed by grading and previous development.

Therefore, while the project site is unlikely to contain intact buried archaeological deposits, it is always possible to encounter resources during project-related ground disturbance. Standard Regulatory Requirements for archaeological resources and human remains have been provided in Section 6.2.

With implementation of these requirements, impacts to archaeological and historical resources would be less than significant. No mitigation measures are required.

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Phase I Cultural Resources Report
23161 Mill Creek Project, Laguna Hills, Orange County
2 September 2025
1 Introduction
South Environmental was retained to complete a cultural resources assessment for the 23161 Mill Creek Project (proposed project, project site) located in the City of Laguna Hills, Orange County, California. This study includes the results of a California Historical Resources Information Center (CHRIS) records search of the project site and a one-half-mile radius; a California Native American Heritage Commission (NAHC) Sacred Lands File search and informational letters to local tribes; and an intensive-level pedestrian survey of the project site by a qualified archaeologist. This study was completed in compliance with the California Environmental Quality Act (CEQA), including Public Resources Code (PRC) Section 5024.1, Title 14 California Code of Regulations (CCR) Section 15064.5 of the CEQA Guidelines, and PRC Sections 21083.2 and 21084.1.

This report was prepared by South Environmental Archaeologist Samantha Jovanovic, MA, MS, Principal Archaeologist Kevin Hunt, BA, and Archaeological Principal Investigator Samantha Murray, MA, RPA, who meets the Secretary of the Interior's Professional Qualification Standards for Prehistoric and Historic Archaeology. Resumes for all authors are provided in Appendix C.

1.1 Project Location
The project site falls within the United States Geological Survey (USGS) San Juan Capistrano, California

7.5-minute quadrangle map in Section 29 of Township 06 South and Range 08 West (Figure 1). The project site encompasses approximately 2.43 acres occupying Assessor’s Parcel Number (APN) 588- 142-07, located at 23161 Mill Creek Drive in the City of Laguna Hills in Orange County, California (Figure 2). The project site is bound by Mill Creek Road to the east and north, parking lots and commercial buildings to the south, and residential development to the west. A school is located across Mill Creek Road to the east. Veeh Reservoir is downslope to the east, below other commercial buildings within Lake Hills Corporate Park.

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Source: ESRI USA Topo Maps and World Topo Map 2024
Figure 1. Project Location Map
¯
0 1,000 2,000 Feet
Project Location is within Laguna Hills, California, in Orange County on the USGS San Juan Capistrano 7.5-minute quadrangle map in Section 29 of Township 06 South and Range 08 West
Center Coordinate (Decimal Degrees):

Latitude: 33.6259973N Longitude: -117.7356113W
Project Site Scale: 1:24,000
23161 Mill Creek Project

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Source: Bing Aerial Imagery 2024
Figure 2. Project Site Detail Map
¯
0 50 100 Feet
Project Site Scale: 1:1,000
23161 Mill Creek Project

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Phase I Cultural Resources Report
23161 Mill Creek Project, Laguna Hills, Orange County
5 September 2025

1.2 Project Description
The proposed project consists of the demolition of the existing office building and associated surface parking lot and landscaping to construct 36 single-family attached condominium residential units, parking, on-site roadways, and associated infrastructure at a density of 14.8 dwelling units per acre (du/ac). Two units will be deed-restricted for very low-income households, while the remaining 34 units are designated as above-moderate income. The proposed project would be constructed on the 2.43- acre parcel located at 23161 Mill Creek Drive. The project site has a City of Laguna Hills General Plan land use designation of Mixed Use and is zoned MXU – Mixed Use.

Architecture
The 36 residential units will feature two plan types – Plan 1 and Plan 2. Each plan type will feature four bedrooms and four bathrooms. Eighteen (18) units will consist of Plan 1, which has a total unit area of 1,991 square feet, while the remaining 18 units will consist of Plan 2, which will have a total unit area of 2,033 square feet. The proposed project has a density of 14.8 du/ac, 64 percent maximum lot coverage, 300 feet minimum lot width, and 360 feet minimum lot depth. The proposed project will also build to a minimum setback of 20 feet to the front, five feet to the side (interior), 20 feet to the side street, and 7.5 feet to the rear. The proposed project also includes 14,500 square feet of private open space in the form of balconies and private yards.

Landscaping
The proposed project includes a landscape coverage of 20 percent and a minimum building separation of 6.5 feet. Landscaping will be distributed throughout the project site in the form of large accent trees, medium accent trees, perimeter screening trees, small accent trees, shrub and groundcover, and vines and espaliers.

Walls/Fences
The proposed project is designed to include a concrete masonry block wall with cap or a mechanically stabilized earth wall surrounding the project site, a 3-foot 6-inch high steel cable guard rail along the western and southern project site boundaries, a 6-feet high split face block wall with precision cap in between each unit, and a 6-feet high tubular steel view fence along the northern and eastern project site boundaries. The entrance will include a 7-feet high cultured stone veneer entry wall with cap.

Utilities
The proposed project includes a series of area drains and catch basins to collect street flow. The southern half of the project site drains out to Mill Creek Drive through a proposed parkway culvert near the proposed driveway. The north half of the project site drains out to Mill Creek Drive through a second proposed parkway culvert near the northeast corner of the project site.

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Phase I Cultural Resources Report
23161 Mill Creek Project, Laguna Hills, Orange County
6 September 2025
Parking/Site Access
The proposed project is designed to provide 90 parking spaces in the forms of attached garages and uncovered parking stalls. Access to the project site is proposed via one full-access gated driveway along Mill Creek Drive. The existing driveway at the project site will be modified to include a gate entry with call box, a monument signage wall, separate entrance and exit points, and fire lane entrance signs.

The driveway will be a minimum of 40 feet wide and features a gated entry and exit.

1.3 Project Study Area
The archaeological study area is the entirety of the approximately 2.43-acre project site and includes all areas where ground disturbance is expected to occur as a result of new construction.

1.4 Regulatory Setting

1.4.1 State
California Register of Historical Resources
In California, the term “historical resource” includes but is not limited to “any object, building, structure, site, area, place, record, or manuscript which is historically or archaeologically significant, or is significant in the architectural, engineering, scientific, economic, agricultural, educational, social, political, military, or cultural annals of California” (California PRC Section 5020.1(j)). In 1992, the California legislature established the CRHR “to be used by state and local agencies, private groups, and citizens to identify the state’s historical resources and to indicate what properties are to be protected, to the extent prudent and feasible, from substantial adverse change” (California PRC Section 5024.1(a)).

The criteria for listing resources on the CRHR were expressly developed to be in accordance with previously established criteria developed for listing in the National Register of Historic Places (NRHP), enumerated below. According to California PRC Section 5024.1(c)(1–4), a resource is considered historically significant if it (i) retains “substantial integrity,” and (ii) meets at least one of the following criteria:
(1) Is associated with events that have made a significant contribution to the broad patterns of California’s history and cultural heritage.
(2) Is associated with the lives of persons important in our past. (3) Embodies the distinctive characteristics of a type, period, region, or method of construction, or represents the work of an important creative individual, or possesses high artistic values.
(4) Has yielded, or may be likely to yield, information important in prehistory or history.

In order to understand the historic importance of a resource, sufficient time must have passed to obtain a scholarly perspective on the events or individuals associated with the resource. A resource less than

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Phase I Cultural Resources Report
23161 Mill Creek Project, Laguna Hills, Orange County
7 September 2025
50 years old may be considered for listing in the CRHR if it can be demonstrated that sufficient time has passed to understand its historical importance (see 14 CCR 4852(d)(2)).

The CRHR protects cultural resources by requiring evaluations of the significance of prehistoric and historic resources. The criteria for the CRHR are nearly identical to those for the NRHP, and properties listed or formally designated as eligible for listing in the NRHP are automatically listed in the CRHR, as are the state landmarks and points of interest. The CRHR also includes properties designated under local ordinances or identified through local historical resource surveys.

California Environmental Quality Act
As described further below, the following CEQA statutes and CEQA Guidelines are of relevance to the analysis of archaeological, historic, and tribal cultural resources:
• California PRC Section 21083.2(g) defines “unique archaeological resource.” • California PRC Section 21084.1 and CEQA Guidelines Section 15064.5(a) define “historical resources.” In addition, CEQA Guidelines Section 15064.5(b) defines the phrase “substantial adverse change in the significance of an historical resource.” It also defines the circumstances when a project would materially impair the significance of an historical resource. • California PRC Section 21074(a) defines “tribal cultural resources.” • California PRC Section 5097.98 and CEQA Guidelines Section 15064.5(e) set forth standards and steps to be employed following the accidental discovery of human remains in any location other than a dedicated ceremony.
• California PRC Sections 21083.2(b)-(c) and CEQA Guidelines Section 15126.4 provide information regarding the mitigation framework for archaeological and historic resources, including examples of preservation-in-place mitigation measures; preservation-in-place is the preferred manner of mitigating impacts to significant archaeological sites because it maintains the relationship between artifacts and the archaeological context and may also help avoid conflict with religious or cultural values of groups associated with the archaeological site(s).

More specifically, under CEQA, a project may have a significant effect on the environment if it may cause “a substantial adverse change in the significance of an historical resource” (California PRC Section 21084.1; CEQA Guidelines Section 15064.5(b).) If a site is either listed or eligible for listing in the CRHR, or if it is included in a local register of historic resources or identified as significant in a historical resources survey (meeting the requirements of California PRC Section 5024.1(q)), it is a “historical resource” and is presumed to be historically or culturally significant for purposes of CEQA (California PRC Section 21084.1; CEQA Guidelines Section 15064.5(a)). The lead agency is not precluded from determining that a resource is a historical resource even if it does not fall within this presumption (California PRC Section 21084.1; CEQA Guidelines Section 15064.5(a)).

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A “substantial adverse change in the significance of an historical resource” reflecting a significant effect under CEQA means “physical demolition, destruction, relocation, or alteration of the resource or its immediate surroundings such that the significance of an historical resource would be materially impaired” (CEQA Guidelines Section 15064.5(b)(1); California PRC Section 5020.1(q)). In turn, CEQA Guidelines section 15064.5(b)(2) states the significance of an historical resource is materially impaired when a project:

1. Demolishes or materially alters in an adverse manner those physical characteristics of an historical resource that convey its historical significance and that justify its inclusion in, or eligibility for, inclusion in the California Register of Historical Resources; or

2. Demolishes or materially alters in an adverse manner those physical characteristics that account for its inclusion in a local register of historical resources pursuant to section 5020.1(k) of the PRC or its identification in an historical resources survey meeting the requirements of section 5024.1(g) of the PRC, unless the public agency reviewing the effects of the project establishes by a preponderance of evidence that the resource is not historically or culturally significant; or

3. Demolishes or materially alters in an adverse manner those physical characteristics of a historical resource that convey its historical significance and that justify its eligibility for inclusion in the California Register of Historical Resources as determined by a lead agency for purposes of CEQA.

Pursuant to these sections, the CEQA inquiry begins with evaluating whether a project site contains any “historical resources,” then evaluates whether that project will cause a substantial adverse change in the significance of a historical resource such that the resource’s historical significance is materially impaired.

If it can be demonstrated that a project will cause damage to a unique archaeological resource, the lead agency may require reasonable efforts be made to permit any or all of these resources to be preserved in place or left in an undisturbed state. To the extent that they cannot be left undisturbed, mitigation measures are required (California PRC Section 21083.2[a], [b], and [c]).

California PRC Section 21083.2(g) defines a unique archaeological resource as an archaeological artifact, object, or site about which it can be clearly demonstrated that without merely adding to the current body of knowledge, there is a high probability that it meets any of the following criteria:

1. Contains information needed to answer important scientific research questions and that there is a demonstrable public interest in that information.

2. Has a special and particular quality such as being the oldest of its type or the best available example of its type.

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3. Is directly associated with a scientifically recognized important prehistoric or historic event or person.

Impacts to non-unique archaeological resources are generally not considered a significant environmental impact (California PRC section 21083.2(a); CEQA Guidelines Section 15064.5(c)(4)).

However, if a non-unique archaeological resource qualifies as tribal cultural resource (California PRC Section 21074(c), 21083.2(h)), further consideration of significant impacts is required. CEQA Guidelines Section 15064.5 assigns special importance to human remains and specifies procedures to be used when Native American remains are discovered. As described below, these procedures are detailed in California PRC Section 5097.98.

California State Assembly Bill 52 (AB 52)
AB 52 amended PRC Section 5097.94 and added PRC Sections 21073, 21074, 21080.3.1, 21080.3.2, 21082.3, 21083.09, 21084.2, and 21084.3. Section 4 of AB 52 adds Sections 21074(a) and (b) to the PRC, which address tribal cultural resources and cultural landscapes. Section 21074(a) defines tribal cultural resources as one of the following:
(1) Sites, features, places, cultural landscapes, sacred places, and objects with cultural value to a California Native American tribe that are either of the following:
(A) Included or determined to be eligible for inclusion in the California Register of Historical Resources.
(B) Included in a local register of historical resources as defined in subdivision (k) of Section 5020.1.
(2) A resource determined by the lead agency, in its discretion and supported by substantial evidence, to be significant pursuant to criteria set forth in subdivision (c) of Section 5024.1. In applying the criteria set forth in subdivision (c) of Section 5024.1 for the purposes of this paragraph, the lead agency shall consider the significance of the resource to a California Native American tribe.

Section 1(a)(9) of AB 52 establishes that “a substantial adverse change to a tribal cultural resource has a significant effect on the environment.” Effects on tribal cultural resources should be considered under CEQA. Section 6 of AB 52 adds Section 21080.3.2 to the PRC, which states that parties may propose mitigation measures “capable of avoiding or substantially lessening potential significant impacts to a tribal cultural resource or alternatives that would avoid significant impacts to a tribal cultural resource.” California Health and Safety Code Section 7050.5
California law protects Native American burials, skeletal remains, and associated grave goods, regardless of their antiquity, and provides for the sensitive treatment and disposition of those remains.

California Health and Safety Code Section 7050.5 requires that if human remains are discovered in any

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place other than a dedicated cemetery, no further disturbance or excavation of the site or nearby area reasonably suspected to contain human remains can occur until the county coroner has examined the remains (Health and Safety Code Section 7050.5(b)). PRC Section 5097.98 also outlines the process to be followed in the event that remains are discovered. If the coroner determines or has reason to believe the remains are those of a Native American, the coroner must contact the NAHC within 24 hours (Health and Safety Code Section 7050.5(c)). The NAHC will notify the “most likely descendant.” With the permission of the landowner, the most likely descendant may inspect the site of discovery. The inspection must be completed within 48 hours of notification of the most likely descendant by the NAHC. The most likely descendant may recommend means of treating or disposing of, with appropriate dignity, the human remains and items associated with Native Americans.

1.4.2 Local
Laguna Hills General Plan
Conservation and Open Space Element
The Conservation and Open Space Element of the Laguna Hills General Plan (City of Laguna Hills 2009) includes discussion and policies regarding the preservation and value of cultural resources. Specifically, this element states “Cultural resources that reflect the history of a community, from descendants of the earliest Native Americans to later explorers, settlers, and immigrants, are important to the community and, therefore, warrant protection by the City.” “The City will continue to review City of Laguna Hills General Plan conservation and Open space COS15 future development proposals to ensure that cultural resources (including prehistoric, historic, and paleontological) are conserved in compliance with CEQA requirements” (City of Laguna Hills 2009).

Policy COS-1.15: Recognize that archaeological and paleontological resources are nonrenewable resources worthy of preservation.

Policy COS-2.7: Promote and expand the link between recreation and educational activities by exploring opportunities tied to sites of paleontological or archaeological interest and other environmentally sensitive areas.

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2 Environmental Setting
Regionally, the project site is located in south Orange County approximately 6.98 miles inland of the Pacific Ocean. Locally, the site is located 1.4 miles south of Interstate 405, 0.8-mile southwest of Interstate 5, 2.55 miles north of State Route 73, and 1.16 miles east of State Route 133. The project site is within a developed urban setting with an existing development throughout the entire project site that includes two office buildings, a parking lot, and ornamental landscaping throughout. The site is also surrounded by dense urban development with similar commercial buildings, parking lots, and a residential neighborhood. Prior to the region’s development, coastal sage scrub, grassland, and south oak woodland plant communities were likely present (Munz and Keck 1975).

The project site is at an elevation of approximately 335 feet above mean sea level (amsl) near the northern edge and slopes upward to 360 feet amsl near the center and south end (USGS 2024). The climate in the region is Mediterranean, with average summer high temperatures (°Fahrenheit) in the low-80s and average winter lows in the mid-40s. Average annual rainfall is approximately 14 inches with most of the precipitation occurring between December and March, with almost no precipitation between June and September (City of Laguna Hills 2024a; NOAA 2024).

The site is located on the eastern flank of the San Joaquin Hills, which are part of the Peninsular Range.

The Peninsular Ranges geomorphic province extends southward from the Los Angeles Basin to the tip of Baja California and is characterized by elongated northwest-trending mountain ranges separated by sediment-floored valleys (Yerkes et al. 1965). The site sits atop the Sespe Formation, a widespread fossiliferous non-marine sedimentary geologic unit intermixed with metamorphosed marine sedimentary rock that formed during the Miocene era. The Sespe Formation includes Oligocene-aged nonmarine (continental) sedimentary rocks, comprised of well consolidated sandstone, shale, and conglomerate Adjacent geologic units include generally unconsolidated, undifferentiated Quaternary alluvium and marine deposits of Pleistocene to Holocene age (California Department of Conservation 2015).

According to the United States Department of Agriculture (USDA) Soils Database there is one major soil complex within the study area (USDA/NRCS 2024): Alo variant clay, 15 to 30 percent slopes. These soils occur in the entire project site and have a parent material of residuum weathered from sedimentary rock (USDA/NRCS 2024).

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3 Cultural Setting

3.1 Prehistoric Context
While many chronological sequences have been developed to describe cultural changes in Southern California, the following builds on Wallace (1955, 1978), who developed a prehistoric chronology for the Southern California coastal region that is still widely used today. Four periods are presented in this sequence: Early Man, Milling Stone, Intermediate, and Late Prehistoric. The summary of prehistoric chronological sequences for Southern California coastal and near-coastal areas presented below is a combination of Wallace (1955) and Warren (1968) as well as more recent studies.

3.1.1 Early Man Horizon (ca. 10,000 – 6,000 B.C.)
Numerous pre-8,000 B.C. sites have been identified along the mainland coast and Channel Islands of Southern California (Moratto 1984; Erlandson 1991; Rick et al. 2001; Johnson et al. 2002; Jones and Klar 2007). The Arlington Springs site on Santa Rosa Island produced human femurs dated to approximately 13,000 years ago (Johnson et al. 2002). The most widely accepted dates for archaeological sites on the southern California coast are from two of the northern Channel Islands, located off the coast of Santa Barbara. On San Miguel Island, Daisy Cave clearly establishes the presence of people in this area about 10,000 years ago (Erlandson 1991:105).

Early Man Horizon sites are generally associated with a greater emphasis on hunting than later horizons. Recent data indicate that the Early Man economy was a diverse mixture of hunting and gathering, including a significant focus on aquatic resources in coastal areas and on inland Pleistocene lakeshores (Moratto 1984).

3.1.2 Milling Stone Horizon (6,000 – 3,000 B.C.)
Set during the Altithermal, which began around 6,000 B.C., the Milling Stone Horizon is characterized by changing subsistence strategies in response to drier climate. This included a greater emphasis on plant foods and small game. Extensive seed processing is evident in the dominance of stone grinding implements in contemporary archaeological assemblages; namely, milling stones (metates) and handstones (manos). The mortar and pestle, associated with acorns or other foods processed through pounding, were first used during the Milling Stone Horizon and increased dramatically in later periods (Wallace 1955, 1978; Warren 1968). Other food resources including small and large terrestrial mammals, sea mammals, birds, shellfish and other littoral and estuarine species, near-shore fishes, yucca, agave, and seeds and other plant products (Kowta 1969). Depending on the environmental setting (coastal or inland), food procurement strategies are found to be highly variable (Byrd and Raab 2007:220).

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3.1.3 Intermediate Horizon (3,000 B.C. – A.D. 500)
The Intermediate Horizon is characterized by a shift toward a hunting and maritime subsistence strategy, as well as greater use of plant foods. During the Intermediate Horizon, a noticeable trend occurred towards a greater adaptation to local resources including a broad variety of fish, land mammals, and sea mammals along the coast. This diversity was reflected in tool kits for hunting, fishing, and processing food and materials, with flake scrapers, drills, various projectile points, and shell fishhooks being manufactured. Mortars and pestles became more common during this period, gradually replacing manos and metates as the dominant milling tool. This change in milling stone technology indicates a transition from the processing and consumption of hard seed resources to the increased reliance on acorns (Glassow et al. 1988; True 1993).

3.1.4 Late Prehistoric Horizon (A.D. 500 – European Contact) The Late Prehistoric Horizon is characterized by an increased diversity of plant food resources and land and sea mammal hunting. Material culture became more complex as demonstrated through more diverse classes of artifacts. During this period, the northern Channel Islands populations further developed craft specializations, including shell bead manufacture, that sustained trade with mainland settlements and with further trading partners to the east, creating a regional economy. Steatite quarried on Santa Catalina Island was used to make stone bowls, pipes, comals, sucking tubes, pendants, beads, and effigies. The lack of pottery in coastal and near-coastal sites implies that ceramic technology was not widely used, or that ceramics were obtained by trade with neighboring groups to the south and east. The lack of widespread pottery manufacture may also be due to the utility of tightly woven and watertight basketry that functioned in much the same way as ceramic vessels.

In areas of inland settlement, by the end of the Intermediate Period, mobility and long-distance migration towards the coast from seasonal camps was replaced by the development of permanent settlements. The period between A.D. 500 and European contact is divided into three regional patterns:

Chumash (Santa Barbara and Ventura counties), Takic/Numic (Los Angeles, Orange, and western Riverside counties), and Yuman (San Diego County). Modern Gabrielino/Tongva, Juaneño, and Luiseño people in this region are considered to be the descendants of the Uto-Aztecan, Takic-speaking populations that settled along the California coast during this period (Warren 1968).

3.2 Ethnographic Context

3.2.1 Gabrielino/Tongva
The project is located within the southern edge of the Gabrielino/Tongva ethnographic territory, less than one mile northwest of Aliso Creek, which is considered the interface with the Juaneño/Acjachemen (Bean and Smith 1978:538; Kroeber 1925: Plate 57). Adjacent Native groups include the Chumash and Tataviam/Alliklik to the north, Serrano and Cahuilla to the east, and Juaneño to the south. Santa Catalina Island (Pimu) and San Clemente Island (Kinki) are located at the western

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extent of Gabrielino ethnographic territory, with the Chumash having occupied most of the northern Channel Islands. The project site is on the eastern flank of the San Joaquin Hills, in the southern end of the traditional Gabrielino/Tongva territory.

Archaeological, linguistic, and genetic evidence documents interaction between the Gabrielino and their neighbors in the form of intermarriage and trade. The term “Gabrielino” denotes those people who were administered by the Spanish at Mission San Gabriel, which included people from the traditional Gabrielino territory as well as other nearby groups (Bean and Smith 1978; Kroeber 1925).

Many modern Gabrielino who identify as descendants of the indigenous people who lived within the Los Angeles Basin refer to themselves as Tongva (King 1994:12), but this term is not universally used.

This term is used in the remainder of this section to refer to the contact period indigenous inhabitants of the Los Angeles Basin and southern Channel Islands and their descendants. Tongva lands encompassed the greater Los Angeles Basin and three Channel Islands: San Clemente, San Nicolas, and Santa Catalina (Bean and Smith 1978:538; Kroeber 1925:636).

The Tongva language belongs to the Takic branch of the Uto-Aztecan language family, which can be traced to the Great Basin region (Mithun 2004). This language family includes dialects spoken by the nearby Juaneño and Luiseño but is considerably different from those of the Chumash people living to the north and the Diegueño (including Ipai, Tipai, and Kumeyaay) people living to the south in modern San Diego and Imperial Counties. Tongva society was organized along patrilineal non-localized clans, a common Takic pattern. Each clan had a ceremonial leader and contained several lineages.

The Tongva established large permanent villages and smaller satellite camps in locations from the San Gabriel Mountains to the southern Channel Islands and throughout the Los Angeles Basin and Santa Ana Plain. Ethnohistoric work conducted by Stephen O’Neil (2002) suggests a total tribal population of nearly 10,000, roughly twice that of earlier estimates (Bean and Smith 1978:540). The Tongva village of Kengaa was located approximately nine miles west of the project site in the vicinity of modern Newport Beach’s back bay (Kroeber 1925; McCawley 1996). The Tongva village of Pasbenga was located approximately nine miles northwest of the project site in modern Santa Ana (Kroeber 1925; McCawley 1996).

Tongva subsistence was oriented around acorns supplemented by the roots, leaves, seeds, and fruits of a wide variety of plants. Meat sources included large and small mammals, freshwater and saltwater fish, shellfish, birds, reptiles, and insects (Bean and Smith 1978; Langenwalter et al. 2001; Kroeber 1925; McCawley 1996). The Tongva employed a wide variety of tools and implements to gather and hunt food. The digging stick, used to extract roots and tubers, was frequently noted by early European explorers (Rawls 1984). Other tools included the bow and arrow, traps, nets, blinds, throwing sticks and slings, spears, harpoons, and hooks. Like the Chumash, the Tongva made oceangoing plank canoes (known as a ti’at) capable of holding six to fourteen people and used for fishing, travel, and trade between the mainland and the Channel Islands. Tule reed canoes were employed for near-shore fishing (Blackburn 1963; McCawley 1996:117-127).

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Chinigchinich, the last in a series of heroic mythological figures, was central to Tongva religious life at the time of Spanish contact (Kroeber 1925:637–638). The religion was spreading south among other Takic-speaking groups at the same time the Spanish were establishing Christian missions. Elements of Chinigchinich suggest it was a syncretic mixture of native and Christian belief and practices (McCawley 1996:143-144).

Prior to European contact and subsequent assimilation, the Tongva practiced burial and cremation funerary traditions. Burial was more common on the Channel Islands and the adjacent mainland coast, while cremation was practiced primarily in the interior (Harrington 1942; McCawley 1996:157). After pressure from Spanish missionaries, cremation essentially ceased during the post-Contact period (McCawley 1996:157).

3.3 Historic Context
Post-Contact history for the state of California is generally divided into three periods: the Spanish Period (1769–1822), Mexican Period (1822–1848), and American Period (1848–present).

3.3.1 Spanish Period (1769–1822)
In search of the legendary Northwest Passage, Spanish explorer Juan Rodríquez Cabríllo stopped in 1542 at present-day San Diego Bay. Cabríllo explored the shorelines of present-day Catalina Island as well as San Pedro and Santa Monica Bays. Much of the present California and Oregon coastline was mapped and recorded in the next half-century by Spanish naval officer Sebastián Vizcaíno. Spain laid claim to California based on the surveys conducted by Cabríllo and Vizcaíno (Bancroft 1885:96–99; Gumprecht 1999:35).

The 1769 overland expedition by Captain Gaspar de Portolá marks the start of California’s Historic period. With a band of 64 soldiers, missionaries, Baja (lower) California Native Americans, and Mexican civilians, Portolá established the Presidio of San Diego, a fortified military outpost, as the first Spanish settlement in Alta California. In July of 1769, while Portolá was exploring southern California, Franciscan Father Junípero Serra founded Mission San Diego de Alcalá at Presidio Hill, the first of the 21 missions that would be established in Alta California by the Spanish and the Franciscan Order between 1769 and 1823.

By the time the Spanish started colonizing Alta California, they had developed an effective system for establishing resilient, long-lasting settlements. With the goal of reaching self-sustainability as quickly as possible, the Spanish used a three-pronged approach comprising military presence to enforce order and mount a defense against attack, commerce for the production and trade of necessary goods, and religion (Kimbro and Costello 2009). This approach was meant to build stable communities that could sustain and protect themselves. With time, these communities expanded into towns and, eventually, modern cities such as San Diego, Santa Barbara, Los Angeles, and San Jose (Kimbro and Costello 2009).

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In 54 years, the Spanish built twenty-one missions, four presidios and three pueblos in Alta California (Kimbro and Costello 2009). The mission system was fraught with successes and failures. As great churches and new crops rose from the ground, often the local Native American people and culture fell to disease and acculturation in droves (Kimbro and Costello 2009:1). However, experiences varied between the missions depending on the managerial personnel, tribal inclinations, and political and environmental events (Kimbro and Costello 2009:1).

In 1774, Juan Bautista de Anza led an overland expedition northward from Sonora, Mexico, to explore the inland areas of California and find an acceptable passage to Monterey in Alta California (National Park Service [NPS] 1996). In October 1775, de Anza led a group of 240 immigrants along the same 1,200-mile route, traversing the San Jacinto Valley and crossing the Santa Ana River near the modern City of Riverside before arriving at Mission San Gabriel in the first week of January 1776 (Anza Trail Foundation 2024). The group successfully made it to Monterey in April 1776 with only one fatality.

Some continued to San Francisco to establish the presidio and mission on the peninsula (NPS 1996).

3.3.2 Mexican Period (1822–1848)
After more than a decade of intermittent rebellion and warfare, New Spain (Mexico and the California territory) won independence from Spain in 1821. In 1822, the Mexican legislative body in California ended isolationist policies designed to protect the Spanish monopoly on trade, and decreed California ports open to foreign merchants (Dallas 1955:14).

Extensive land grants were established in the interior during the Mexican Period, in part to increase the population inland from the more settled coastal areas where the Spanish had first concentrated their colonization efforts (Dallas 1955). The secularization of the missions following Mexico’s independence from Spain resulted in the subdivision of former mission lands and establishment of many additional ranchos. During the supremacy of the ranchos (1834–1848), landowners largely focused on the cattle industry and devoted large tracts to grazing. Cattle hides became a primary southern California export, providing a commodity to trade for goods from the east and other areas in the United States and Mexico. The number of nonnative inhabitants increased during this period because of the influx of explorers, trappers, and ranchers associated with the land grants. The rising California population contributed to the introduction and rise of diseases foreign to the Native American population, who had no associated immunities.

In 1842, Rancho Niguel was established in a 13,000-acre land grant to Juan Avila that included modern day cities along Aliso Creek such as Laguna Hills, Aliso Viejo, Laguna Niguel, and Dana Point on which Avila raised cattle herds. After the Mexican-American War, Avila was able to patented his land claim with the United States government (Laguna Beach Historical Society 2024).

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3.3.3 American Period (1848–Present)
The Mexican–American War ended with the Treaty of Guadalupe Hidalgo in 1848, ushering California into its American Period. California officially became a state with the Compromise of 1850, which also designated Utah and New Mexico (with present-day Arizona) as U.S. Territories.

The Gold Rush began in 1848, and with the influx of people seeking gold, cattle were no longer desired mainly for their hides but also as a source of meat and other goods. During the 1850s cattle boom, rancho vaqueros drove large herds from southern to northern California to feed that region’s burgeoning mining and commercial boom. The cattle boom ended for southern California as neighbor states and territories drove herds to northern California at reduced prices. Operation of the huge ranchos became increasingly difficult, and droughts severely reduced their productivity (Cleland 2005:102–103).

Orange County
In July 1769, the Portolá expedition traversed the region that became Orange County (Smith 1965).

Portolá named the area El Valle de Santa Ana (the Valley of Santa Ana). After Mexican independence from Spain, few ranchos in the future Orange County were granted to Mexican citizens who would cultivate land for the government. After the secularization of the missions by the Mexican government in 1933, nine additional ranchos were granted between 1837 and 1846 (Middlebrook 2024).

The future Orange County remained dominated by ranches in the early American period. 1n 1862, however, a disastrous flood, smallpox outbreak, and subsequent drought resulted in many large ranch owners as well as farmers losing their properties through inability to pay taxes (Middlebrook 2024).

Many of the large ranches were broken up and townships plotted throughout the Santa Ana Valley including Anaheim (1857), Santa Ana (1870), and Orange (1870) (Dumke 1970[1944]:112-115). The Santa Fe Railroad reached Anaheim in 1887, the same year that the Southern Pacific Railroad reached Santa Ana.

The County of Orange was established in 1889 from a 780-acre portion of Los Angeles County that included 40 miles of coastline and some of the best citrus groves in Southern California (Dumke 1970[1944]:118).

Despite significant population growth throughout the early twentieth century, Orange County largely retained its agricultural character. After World War II, inadequate housing supply due to a population boom resulted in many of the agricultural fields and groves being replaced by suburban housing tracts.

Construction of the Santa Ana Freeway (Interstate 5) in the 1950s and the Riverside Freeway (State Highway 91) in the early 1960s established further transportation routes to and through Orange County. With its mild climate, miles of beach, and development of amusement parks such as Disneyland and Knott’s Berry Farm, the county became known as a tourist destination in the late

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twentieth century. In the twenty-first century Orange County continues development and redevelopment of aging urban and suburban areas.

Laguna Hills (post-1830s)
During Spanish and throughout Mexican occupation, the area around Laguna Hills was used for grazing herds of cows with large land grants forming Rancho San Joaquin, Rancho Loma de Santiago, and Rancho Niguel (City of Laguana Hills 2024b). When cattle became unprofitable, sheep took their place. Lewis Moulton from Boston leased Rancho Niguel in 1874 and purchased it in 1895 along with 9,000 more acres, increasing the Rancho from Don Juan Avila’s original 13,000 to 22,000 acres. Moulton and his business partner Jean Pierre Daguerre raised sheep, cattle, and crops on the land. This use was continued into the twentieth century until the 1960s when the land was broken up into smaller lots and developed for residential and commercial use (City of Laguna Hills 2024b). Laguna Hills became an official city in 1991 and annexed North Laguna Hills in 1995 (City of Laguna Hills 2024b).

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4 Background Research

4.1 CHRIS Records Search
On December 4, 2024, South Environmental archaeologist Samantha Jovanovic performed a cultural resources records search of the project site and a one-half-mile search radius at the South Central Coastal Information Center (SCCIC), which houses cultural resources records for Orange County. This search included their collections of mapped prehistoric and historic archaeological resources and historic built-environment resources, State of California Department of Parks and Recreation Site Records (DPR forms), technical reports, archival resources, and ethnographic references. Additional consulted sources include historical maps of the study area, the NRHP, the CRHR, the lists of California State Historical Landmarks, California Points of Historical Interest, and the Archaeological Determinations of Eligibility list. A summary of the results of the records search is presented in Appendix A.

4.1.1 Previously Conducted Cultural Resource Studies
The SCCIC records search results indicate that two previously conducted cultural resource studies intersect the project site. A summary of these studies is provided following Table 1. An additional 24 studies were identified outside the project site within the one-half-mile records search radius. A list of all previously conducted studies identified within the records search radius is provided in Table 1.

Table 1. Previous Cultural Resources Investigations Within 0.5-Mile of the Project Site SCCIC
Report
Number
Author Year Report Title Proximity to
Project Site
OR-00066 Desautels, Roger
J.
1976 Archaeological Survey Reports on Ridge Route Drive and Moulton Parkway (VEEH Reservoir) Road
Widening and Installation, Laguna Hills Area,
Orange County, California
Outside
(Approximately

0.33-mi E)
OR-00143 Desautels, Roger
J.
1976 Archaeological Survey Report on 85(+ Or -) Acres of Land Located in the Laguna Hills Area of the County
of Orange Tract No's 9610, 9611, 9612, and 9613
Outside
(Approximately

0.02-mi SW)
OR-00274 Anonymous 1978 Report of Archaeological Resources Survey Conducted for Laguna and Peter's Canyons
Outside
(Approximately

0.33-mi W)
OR-00305 Schroth, Adella 1979 The History of Archaeological Research on Irvine Ranch Property: The Evolution of a Company
Tradition
Outside
(Approximately

0.28-mi N)
OR-00737 Padon, Beth 1984 Cultural Resources Assessment Planning Area 34b Orange County, California
Outside
(Approximately

0.26-mi N)

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Table 1. Previous Cultural Resources Investigations Within 0.5-Mile of the Project Site SCCIC
Report
Number
Author Year Report Title Proximity to
Project Site
OR-00742 Padon, Beth 1984 Historic Property Survey Report for Irvine Center Drive Widening
Outside
(Approximately

0.26-mi N)
OR-00841 Mason, Roger D. 1986 Archaeological, Historical, and Paleontological Assessments for Planning Area 34b, City of Irvine
Outside
(Approximately

0.26-mi N)
OR-00847 Padon, Beth 1985 Archaeological Resource Inventory City of Irvine and its Sphere of Influence
Outside
(Approximately

0.37-mi N)
OR-00945 Van Horn, David
M.
1982 Rossmoor Business Park Liquidating Trust Properties Outside (Approximately

0.29-mi SE)
OR-01032 White, Robert S. 1990 Archaeological Resource Assessment Two Road Alignments Within Village 34 Lake Forest Drive and
Bake Parkway Orange County, California
Outside
(Approximately

0.49-mi NW)
OR-01109 Padon, Beth 1986 Addendum to the Historic Property Survey Report for Irvine Center Drive Widening
Outside
(Approximately

0.26-mi N)
OR-01127 Rosenthal, Jane 1991 Past to Present: Cultural and Scientific Resources, an Archival Inventory Irvine Ranch Open Space Reserve
Orange County, California
Outside
(Approximately

0.49-mi WSW)
OR-01129 Van Horn, David
M.
1982 Cultural Resource Assessment: the Koll Property
Near Laguna Hills; a Possible Annexation Area for
the City of Irvine and its Sphere of Influence
Within
OR-01344 Rosenthal, Jane 1993 Cultural Resources Element City of Laguna Hills, Orange County, California Within
OR-02225 Strozier, Hardy 1978 The Irvine Company Planning Process and California Archaeology- A Review and Critique
Outside
(Approximately

0.32-mi W)
OR-02267 Hunt, Kevin P. and
Brian F. Smith
2000 An Archaeological and Paleontological Survey of the Irvine Spectrum GPA Project
Outside
(Approximately

0.26-mi N)
OR-02336 Demcak, Carol R.
and Milos
Velechovsky
2000 Final Report on Archaeological and Paleontological Monitoring Program Conducted at Spectrum 5,
Irvine, Orange County, California
Outside
(Approximately

0.26-mi N)
OR-02406 Duke, Curt 2001 Review of Cingular Wireless Facility SC 008-02 Outside (Approximately

0.25-mile SE)
OR-02534 unknown 1976 Annual Report to The Irvine Company from Archaeological Research, Inc.

Outside
(Approximately

0.26-mi N)
OR-02626 Younger, Shannon
and Smith, Brooks
2003 Results of Archaeological Construction Monitoring
Planning Area 27 Needlegrass Creek Conservation
Area, Irvine, California
Outside
(Approximately

0.34-mi W)

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Phase I Cultural Resources Report
23161 Mill Creek Project, Laguna Hills, Orange County
21 September 2025
Table 1. Previous Cultural Resources Investigations Within 0.5-Mile of the Project Site SCCIC
Report
Number
Author Year Report Title Proximity to
Project Site
OR-02639 Drover,
Christopher E.
1998 A Cultural Resources Inventory in Planning Area 18 Irvine, California
Outside
(Approximately

0.32-mi W)
OR-03358 Archer, Gavin H.,
Sarah A. Siren,
Lawrence G.

Barnes, Andrew
Schmidt, and
Noelle Shaver
2005 Historical, Archaeological and Paleontological
Resources Identification and Evaluation for the
Planning Area 18 Project Including Impacts Analysis
and Mitigation Measures
Outside
(Approximately

0.32-mi W)
OR-03467 Bonner, Wayne H.
and Sarah A.

Williams
2006 Cultural Resource Records Search Results and Site
Visit for Cingular Telecommunications Facility
Candidate OC0175 (Laguna Village HOA) 23441
Avenida Costanero, Laguna Hills, Orange County,
California
Outside
(Approximately

0.3-mile SW)
OR-03743 Losee, Carolyn 2009 Cultural Resources Investigation for T-Mobile LA02880E "Maxwell" 88 Maxwell, Irvine, Orange
County, California 92618
Outside
(Approximately

0.33-mi N)
OR-04107 Archer, Gavin H.,
David C. Hanna,
and Mark R.

Deering
2007 Cultural Resources Field Assessment for the Lake
Forest Drive and Bake Parkway Extensions Project in
City of Irvine Planning Area 34
Outside
(Approximately

0.37-mi NW)
OR-04289 Stone, David and
Victorino, Ken
2012 Archaeological Survey Report Tertiary Treatment
Plant and Recycled Water Distribution System
Expansion Project Laguna Hills and Laguna Woods,
Orange County, California
Outside
(Approximately

0.18-mi NW)
OR-01129
Cultural Resource Assessment: the Koll Property Near Laguna Hills; a Possible Annexation Area for the City of Irvine and its Sphere of Influence (David M. Van Horn 1982). This study by Archaeological Associates includes a records search for three project areas and a pedestrian survey of one project area. The current project site was not surveyed as part of this study; however, the records search identified one prehistoric archaeological resource southeast of the current project site (P-30-000432 [CA-ORA-432]). This study included a field inspection of P-30-000432 and stated that the site was “completely destroyed by grading operations conducted in connection with construction of an office building complex.” The site is described in Section 4.1.2 below.

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Phase I Cultural Resources Report
23161 Mill Creek Project, Laguna Hills, Orange County
22 September 2025
OR-01344
Cultural Resources Element City of Laguna Hills, Orange County, California (Jane Rosenthal 1993). This study presents the results of a records search and literature review for the entire city of Laguna Hills.

The study includes the current project site; however, no survey was conducted as part of the study.

4.1.2 Previously Recorded Cultural Resources
The SCCIC records search results indicate that one previously recorded cultural resource (P-30-000432 [CA-ORA-432]) was located within one-half-mile of the project site; however, this resource was destroyed by development prior to 1982. No additional resources were identified within the 0.5-mile records search radius.

P-30-000432
This prehistoric archaeological site (also identified as CA-ORA-432) was recorded by C. Reeves and J.B.

Houser in 1973. The site is a surface scatter of flaked and ground stone tools, as well as one marine shell fragment. Flaked artifacts identified include choppers and a scraper plane. Ground stone artifacts include a mano and a metate rim fragment. One fragment of Pecten spp. marine shell was also observed. No site dimensions or sketch map were included in the record. David Van Horn’s (1982), “Cultural Resource Assessment: the Koll Property Near Laguna Hills; a Possible Annexation Area for the City of Irvine and its Sphere of Influence,” stated that P-30-000432 was completely destroyed and the “area graded off completely.”

4.2 Native American Scoping
A Native American Heritage Commission (NAHC) Sacred Lands File search was requested by South Environmental on November 15, 2024. The NAHC responded to the request on December 5, 2024, and reported negative results (i.e., no sacred lands or resources important to Native Americans are recorded in the vicinity of the project). The NAHC recommended contacting the Native American tribes listed in Table 1, for additional information or knowledge they may have regarding the presence of cultural resources that may be impacted by the proposed project. On December 5, 2024, South Environmental sent letters to each contact provided by the NAHC.

As summarized in Table 3, three tribal groups have responded to the outreach letters to date. No archaeological, historical, or tribal cultural resources were identified within the project site as a result of South Environmental’s coordination with tribes and none of the responses expressed concern regarding the proposed project (see Table 3 below). All Native American outreach completed by South Environmental is documented in Appendix B.

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Phase I Cultural Resources Report
23161 Mill Creek Project, Laguna Hills, Orange County
23 September 2025
Table 2. Summary of Native American Outreach
Native American Tribal Contact Method of
Notification/Date Response Received
Cahuilla Band of Indians
Anthony Madrigal, Tribal Historic
Preservation Officer
Cultural Affiliation: Cahuilla
Letter sent via email on
December 5, 2024.

BobbyRay Esparza responded on
December 18, 2024, behalf of Cahuilla
Band of Indians. See below.

Cahuilla Band of Indians
Erica Schenk, Chairperson
Cultural Affiliation: Cahuilla
Letter sent via email on
December 5, 2024.

BobbyRay Esparza responded on
December 18, 2024, behalf of Cahuilla
Band of Indians. See below.

Cahuilla Band of Indians
BobbyRay Esparza, Cultural Director
Cultural Affiliation: Cahuilla
Letter sent via email on
December 5, 2024.

Responded on December 18, 2024,
behalf of Cahuilla Band of Indians: “The
Cahuilla Bans will defer this project to
the Gabrielino/Tongva tribes.”
Gabrieleño Band of Mission Indians - Kizh
Nation
Christina Swindall Martinez, Secretary
Cultural Affiliation: Gabrieleño
Letter sent via email on
December 5, 2024.

No response to date.

Gabrieleño Band of Mission Indians - Kizh
Nation
Andrew Salas, Chairperson
Cultural Affiliation: Gabrieleño
Letter sent via email on
December 5, 2024.

No response to date.

Gabrieleño/Tongva San Gabriel Band of
Mission Indians
Anthony Morales, Chairperson
Cultural Affiliation: Gabrieleño
Letter sent via email on
December 5, 2024.

No response to date.

Gabrielino Tongva Indians of California
Tribal Council
Christina Conley, Cultural Resource
Administrator
Cultural Affiliation: Gabrielino
Letter sent via email on
December 5, 2024.

No response to date.

Gabrielino Tongva Indians of California
Tribal Council
Robert Dorame, Chairperson
Cultural Affiliation: Gabrielino
Letter sent via email on
December 5, 2024.

No response to date.

Gabrielino/Tongva Nation
Sandonne Goad, Chairperson
Cultural Affiliation: Gabrielino
Letter sent via email on
December 5, 2024.

No response to date.

Gabrielino-Tongva Tribe
Charles Alvarez, Chairperson
Cultural Affiliation: Gabrielino
Letter sent via email on
December 5, 2024.

No response to date.

Gabrielino-Tongva Tribe
Sam Dunlap, Cultural Resource Director
Cultural Affiliation: Gabrielino
Letter sent via email on
December 5, 2024.

No response to date.

Juaneño Band of Mission Indians
Sonia Johnston, Chairperson
Cultural Affiliation: Juaneño
Letter sent via email on
December 5, 2024.

No response to date.

Juaneño Band of Mission Indians
Acjachemen Nation - Belardes
Joyce Perry, Cultural Resource Director
Cultural Affiliation: Juaneño
Letter sent via email on
December 5, 2024.

No response to date.

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Phase I Cultural Resources Report
23161 Mill Creek Project, Laguna Hills, Orange County
24 September 2025
Table 2. Summary of Native American Outreach
Native American Tribal Contact Method of
Notification/Date Response Received
Juaneño Band of Mission Indians
Acjachemen Nation 84A
Heidi Lucero, Chairperson, THPO
Cultural Affiliation: Juaneño
Letter sent via email on
December 5, 2024.

No response to date.

La Jolla Band of Luiseno Indians
Norma Contreras, Chairperson
Cultural Affiliation: Luiseno
Letter sent on
December 6, 2024.

No response to date.

Pala Band of Mission Indians
Christopher Nejo, Legal Analyst/Researcher
Cultural Affiliation: Cupeno
Luiseno
Letter sent via email on
December 5, 2024.

Shasta Gaughen responded on behalf of
the Pala Band of Mission Indians on
December 12, 2024. See below.

Pala Band of Mission Indians
Alexis Wallick, Assistant THPO
Cultural Affiliation: Cupeno
Luiseno
Letter sent via email on
December 5, 2024.

Shasta Gaughen responded on behalf of
the Pala Band of Mission Indians on
December 12, 2024. See below.

Pala Band of Mission Indians
Shasta Gaughen, Tribal Historic Preservation
Officer
Cultural Affiliation: Cupeno
Luiseno
Letter sent via email on
December 5, 2024.

Responded on behalf of the Pala Band
of Mission Indians on December 12,
2024, stating the project is outside the
tribes’ Traditional Use Area and,
therefore they “have no objection to the
continuation of project activities as
currently planned and we defer to the
wishes of Tribes in closer proximity to
the project area.”
Pauma Band of Luiseno Indians
Temet Aguilar, Chairperson
Cultural Affiliation: Luiseno
Letter sent via email on
December 5, 2024.

No response to date.

Santa Rosa Band of Cahuilla Indians
Steven Estrada, Tribal Chairman
Cultural Affiliation: Cahuilla
Letter sent via email on
December 5, 2024.

Vanessa Minott responded on behalf of
the Santa Rosa Band on December 9,
2024. See below.

Santa Rosa Band of Cahuilla Indians
Vanessa Minott, Tribal Administrator
Cultural Affiliation: Cahuilla
Letter sent via email on
December 5, 2024.

Responded on behalf of the Santa Rosa
Band on December 9, 2024: “We defer
any comments to Soboba Band of
Luiseno Indians cultural resource
department.”
Soboba Band of Luiseno Indians
Joseph Ontiveros, Tribal Historic
Preservation Officer
Cultural Affiliation: Cahuilla, Luiseno
Letter sent via email on
December 5, 2024.

No response to date.

Soboba Band of Luiseno Indians
Jessica Valdez, Cultural Resource Specialist
Cultural Affiliation: Cahuilla, Luiseno
Letter sent via email on
December 5, 2024.

No response to date.

4.3 Historical Topographic Map and Aerial Photograph Review Historic topographic maps and aerial photographs of the project site were reviewed from Nationwide Environmental Title Research LLC and USGS National Geologic Map Database. These included

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Phase I Cultural Resources Report
23161 Mill Creek Project, Laguna Hills, Orange County
25 September 2025
topographic maps for the years 1901, 1902, 1904, 1942, 1943, 1947, 1948, 1949, 1956, 1957, 1959, 1960, 1963, 1965, 1966, 1968, 1969, 1974, 1983, and 1986; aerial imagery for the years 1938, 1946, 1952, 1963, 1967, 1972, 1980, 1981, 1985, 1987, 1988, 1992, and 1993, (NETR 2024, USGS 2024c).

The earliest topographic maps from 1901 depict the proposed project site as open space (USGS 2024c).

From the earliest aerial photograph (1932) through 1972 the project site and surrounding area were agricultural land (NETR 2024). Veeh Reservoir, to the east of the project site, is first depicted on the 1942 (1943 ed.) Santiago Peak, California topographic map. By 1980, the area west of Mill Creek Drive was developed with residences. The extant building in the project site is visible in the 1987 aerial photograph (NETR 2024).

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Phase I Cultural Resources Report
23161 Mill Creek Project, Laguna Hills, Orange County
26 September 2025
5 Archaeological Survey

5.1 Methods and Results
South Environmental cultural resource specialist Samantha Jovanovic MA, MS, conducted an intensivelevel pedestrian survey of the project site on December 4, 2024. Fieldwork included taking field notes, photography, and examination of close-scale field maps. Photographs were taken with an iPhone 12 camera and Solocator Photography app.

During the archaeological survey, all exposed ground surface for the presence of prehistoric artifacts (e.g., flaked stone tools, tool-making debris, ground stone artifacts tools), historical artifacts (e.g., metal, glass, ceramics), sediment discolorations that might indicate the presence of a cultural midden, depressions, and other features that might indicate the former presence of structures or buildings (e.g., post holes, foundations).

No archaeological resources were identified within the project site during the intensive-level pedestrian survey. The project site consists of a fully developed lot with a multi-story office building, a parking lot, and landscaped islands with non-native grasses, flowers, and trees (Photograph 1-5). There is a landscaped outdoor patio area east of the office building with an assortment of plants and decorative hardscaping (Photograph 6-7). Most of the project site is flat but for a steep grade drop at the northern edge of the project site (Photograph 8). Ground surface visibility was very poor, at approximately 5 percent throughout the project site due to the project site being a fully developed lot with existing building and a parking lot.

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Phase I Cultural Resources Report
23161 Mill Creek Project, Laguna Hills, Orange County
27 September 2025
Photograph 1 Overview along eastern side from southwest corner. View north.

Photograph 2 Overview of site from southwest corner. View northeast.

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Phase I Cultural Resources Report
23161 Mill Creek Project, Laguna Hills, Orange County
28 September 2025
Photograph 3 Overview along southern portion from southwest corner. View east.

Photograph 4 Overview along eastern portion from southeast corner. View north.

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Phase I Cultural Resources Report
23161 Mill Creek Project, Laguna Hills, Orange County
29 September 2025
Photograph 5 Overview from southeast corner. View northwest.

Photograph 6 Landscaped outdoor patio east of building.

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Phase I Cultural Resources Report
23161 Mill Creek Project, Laguna Hills, Orange County
30 September 2025
Photograph 7 Outdoor patio space east of building with decorative plants. View south.

Photograph 8 Steep drop-off north of building. View north.

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Phase I Cultural Resources Report
23161 Mill Creek Project, Laguna Hills, Orange County
31 September 2025
6 Findings and Recommendations

6.1 Findings
No archaeological resources were identified within the project site as a result of the CHRIS records search, NAHC Sacred Lands File search, Native American scoping, or pedestrian survey by a qualified archaeologist. Further, significant portions of the project site have been disturbed by grading and the development of the existing office building and parking lot. Therefore, while the project site is unlikely to contain intact buried archaeological deposits, it is always possible to encounter resources during project-related ground disturbance. The City’s Standard Regulatory Requirements for archaeological resources and human remains have been provided below. With implementation of these requirements, impacts to archaeological and historical resources would be less than significant. No mitigation measures are required.

6.2 Standard Regulatory Requirements
California Administrative Code, Title 14, Section 4308 (14 CCR § 4308) (Accommodation for Unanticipated Cultural/Paleontological Resources). In compliance with the California Code of Regulations, during ground disturbance or any other construction activity, no person shall remove, injure, deface, or destroy any object of archaeological, or historical interest or value.

California Health and Safety Code, and Public Resources Code (Human Remains). In the event that human remains are discovered, there shall be no disposition of such human remains, other than in accordance with the procedures and requirements set forth in California Health and Safety Code Section 7050.5 and Public Resources Code Section 5097.98. These code provisions require notification of the County Coroner and the Native American Heritage Commission, who in turn must notify those persons believed to be most likely descended from the deceased Native American for appropriate disposition of the remains. Excavation or disturbance may continue in other areas of the Project site that are not reasonably suspected to overlie adjacent remains or archaeological resources.

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23161 Mill Creek Project, Laguna Hills, Orange County
32 September 2025
7 Bibliography
Bancroft, Hubert Howe. 1885. History of California, Volume III: 1825-1840. A.L. Bancroft & Co., San Francisco.

Bean, Lowell John and Charles R. Smith. 1978. Gabrielino. In California, edited by Robert F. Heizer, pp. 538-549. Handbook of North American Indians, Vol. 8, W.C. Sturtevant, general editor, Smithsonian Institution, Washington, D.C.

Blackburn, Thomas. 1963. Ethnohistoric Descriptions of Gabrielino Material Culture. Annual Report, Archaeological Survey. University of California, Los Angeles.

Byrd, B.F. and L. Mark Raab. 2007. Prehistory of the Southern Bight: Models for a New Millennium. In California Prehistory, edited by Terry L. Jones and Kathryn A. Klar, pp. 215-228. Altamira Press, New York.

California Department of Conservation. 2015. Geologic Map of California. Interactive Online Map.

Online resource: https://maps.conservation.ca.gov/cgs/gmc/, accessed February 19, 2024.

Cleland, Robert Glass. 2005. The Cattle on a Thousand Hills: Southern California, 1850-80, second ed., sixth printing. The Huntington Library, San Marino, California.

Dallas, S. F. 1955. The Hide and Tallow Trade in Alta California 1822–1848. Ph.D. dissertation, Indiana University, Bloomington.

Dumke, Glenn S. 1944. The Boom of the Eighties in Southern California. Fifth printing, 1970.

Huntington Library Publications, San Marino, California.

Erlandson, J.M. 1991. Early Maritime Adaptations on the Northern Channel Islands. In HunterGatherers of Early Holocene Coastal California, edited by J. M. Erlandson and R. Colten.

Perspectives in California Archaeology, Vol. 1. Institute of Archaeology, University of California, Los Angeles.

Glassow, M.A., L. Wilcoxen, and J. M. Erlandson. 1988. Cultural and Environmental Change during the Early Period of Santa Barbara Channel Prehistory. In The Archaeology of Prehistoric Coastlines, edited by G. Bailey and J. Parkington pp. 64–77. Cambridge University Press, Cambridge, England.

Gumprecht, Blake. 1999. The Los Angeles River: Its Life, Death, and Possible Rebirth. The Johns Hopkins University Press, Baltimore, Maryland.

Harrington, John P. 1942. Fieldwork among the Indians of California. In: Explorations and Fieldwork of the Smithsonian Institution in 1934, pp. 81-84. Washington, DC. 1985 John P. Harrington Papers.

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Johnson, J. R., T. W. Stafford, Jr., H. O. Ajie, and D. P. Morris. 2002. Arlington Springs Revisited. In Proceedings of the Fifth California Islands Symposium, edited by D. Browne, K. Mitchell, and H.

Chaney, pp. 541–545. USDI Minerals Management Service and The Santa Barbara Museum of Natural History, Santa Barbara, California.

Jones, Terry L. and Kathryn A. Klar. 2007. California Prehistory: Colonization, Culture, and Complexity.

AltaMira Press, Lanham, Maryland.

Kimbro, Edna E. and Juila G. Costello. 2009. San Juan Capistrano. In The California Missions: History, Art, and Preservation, edited by Tevvy Ball. Getty Publications, Los Angeles.

King, Chester D. 1994. Native American Placenames in the Santa Monica Mountains National Recreational Area, Agoura Hills. Topanga Anthropological Consultants, Topanga, California.

Kowta, Makoto. 1969. The Sayles Complex, A Late Milling Stone Assemblage from the Cajon Pass and the Ecological Implications of its Scraper Planes. University of California Publications in Anthropology 6:35–69. Berkeley, California.

Kroeber, Alfred J. 1925. Handbook of the Indians of California. Bureau of American Ethnology Bulletin

78. Dover Publications, Inc., New York.

Laguna Hills, City of. 2009. Laguna Hills General Plan. Online resource: https://www.ci.lagunahills.ca.us/DocumentCenter/View/133/Laguna-Hills-General-Plan, accessed February 20, 2024 Laguna Hills, City of. 2024a. Laguna Hills Weather Fast Facts. Online resource:
https://lagunahills.com/weather/, accessed May 7, 2024.

Laguna Hills, City of. 2024b. History of Laguna Hills. Online resource: https://ci.lagunahills.ca.us/247/History-of-Laguna-Hills, accessed May 30, 2024.

Langenwalter, Paul E., II, Mathew A Boxt, Lawrence M. Boxt, M.D., and Theodore T. Miller, M.D. 2001. A Sea Otter (Enhydra lutris) Femur with Embedded Projectile Point Fragment from a Late Prehistoric Camp Site in Long Beach, California. Pacific Coast Archaeological Society Quarterly 37(1).

McCawley, William. 1996. The First Angelinos: The Gabrielino Indian of Los Angeles. Malki Museum Press, Banning, California.

Middlebrook, John-Robin. 2024. History of Orange County, California. Online resource:
https://www.legendsofamerica.com/ca-orangecounty/, accessed February 19, 2024.

Mithun, Marianne. 2004 [1999]. The Languages of Native North America. Reprinted 2004. Cambridge University Press, Cambridge, Massachusetts.

Moratto, Michael. 1984. California Archaeology. Academic Press, New York.

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Munz, Philip A. and David D. Keck. 1975. A California Flora and Supplement. Combined Second Edition Printing. University of California Press, Berkeley, California.

Nationwide Environmental Title Research LLC (NETR). 2024. Historic Aerial Photographs and Topographic Maps. https://www.historicaerials.com/viewer, accessed November 18, 2024.

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Electronic resource, https://www.ncei.noaa.gov/access/us-climate-normals/, accessed May 7, 2024.

O’Neil, Stephen. 2002. The Acjachemen in the Franciscan Mission System: Demographic Collapse and Social Change. Master’s thesis, Department of Anthropology, California State University, Fullerton.

Rawls, James J. 1984. Indians of California: The Changing Image. University of Oklahoma Press, Norman, Oklahoma.

Rick, T.C., Jon M. Erlandson, and René Vellanoweth. 2001. Paleocoastal Marine Fishing on the Pacific Coast of the Americas: Perspectives from Daisy Cave, California. American Antiquity 66:595–613.

Smith, Helen C. 1965. The Portola Camps Revisited. In The Portola Expedition 1769. Orange County Historic Society, California.

True, D.L. 1993. Bedrock Milling Elements as Indicators of Subsistence and Settlement Patterns in Northern San Diego County, California. In Pacific Coast Archaeological Society Quarterly 29(2):1–

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https://websoilsurvey.sc.egov.usda.gov/App/HomePage.htm, accessed November 18, 2024.

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Washington, DC. Online resource: http://ngmdb.usgs.gov/topoview/viewer/#4/40.01/-100.06, accessed May 30, 2024.

Van Horn, David. 1982. Cultural Resource Assessment: the Koll Property Near Laguna Hills; a Possible Annexation Area for the City of Irvine and its Sphere of Influence. Archaeological Associates. On file at the South Central Coastal Information Center, Fullerton, California.

Wallace, William J. 1955. Suggested Chronology for Southern California Coastal Archaeology.

Southwestern Journal of Anthropology 11:214–230.

Wallace, William J. 1978. Post-Pleistocene Archaeology, 9000 to 2000 B.C. In California, edited by Robert F. Heizer, pp. 25–36. Handbook of North American Indians, Vol. 8, William G. Sturtevant, general editor, Smithsonian Institution, Washington D.C.

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23161 Mill Creek Project, Laguna Hills, Orange County
35 September 2025
Warren, Claude N. 1968. Cultural Tradition and Ecological Adaptation on the Southern California Coast. In Archaic Prehistory in the Western United States, edited by Cynthia Irwin-Williams, pp. 1–

14. Eastern New Mexico University Contributions in Anthropology No. 1, Portales, New Mexico.

Yerkes, R.F., T. H. McCulloh, J. E. Schoellhamer, and J. G. Vedder. 1965. Geology of the Los Angeles Basin, California – an Introduction. U. S. Geological Survey Professional Paper 420-A, Pg. 57 .

Online resource: https://pubs.usgs.gov/pp/0420a/report.pdf, accessed May 30, 2024.

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Appendix A:

Records Search Results Summary

Page 1187 of 1727 ends

Report List
Report No. Other IDs Year Author(s) Title Affiliation Resources OR-00066 1976 Archaeological Survey Reports on Ridge
Route Drive and Moulton Parkway (VEEH
Resrvoir) Road Widening and Installation,
Laguna Hills Area, Orange County, California
Scientific Resource
Surveys, Inc.

Desautels, Roger J.

OR-00143 1976 Archaeological Survey Report on 85(+ Or -) Acres of Land Located in the Laguna Hills
Area of the County of Orange Tract No's
9610, 9611, 9612, and 9613
Scientific Resource
Surveys, Inc.

Desautels, Roger J.

OR-00274 1978 Report of Archaeological Resources Survey Conducted for Laguna and Peter's Canyons
Archaeological Resource
Management Corp.

Anonymous 30-000184, 30-000305, 30-000306,
30-000307, 30-000308, 30-000309,
30-000314, 30-000317, 30-000502,
30-000508, 30-000547, 30-000548,
30-000556, 30-000557, 30-000681,
30-000682, 30-000688, 30-000767,
30-000768, 30-000769
OR-00305 1979 The History of Archaeological Research on Irvine Ranch Property: the Evolution of a
Company Tradition
Archaeological Resource
Management Corp.

Schroth, Adella 30-000002, 30-000044, 30-000047,
30-000048, 30-000051, 30-000053,
30-000059, 30-000060, 30-000061,
30-000062, 30-000063, 30-000064,
30-000065, 30-000066, 30-000067,
30-000068, 30-000069, 30-000070,
30-000071, 30-000072, 30-000073,
30-000077, 30-000091, 30-000099,
30-000100, 30-000104, 30-000106,
30-000107, 30-000109, 30-000111
OR-00737 1984 Cultural Resources Assessment Planning
Area 34b Orange County, California
Paleo - Padon, Beth LSA Associates, Inc.

OR-00742 1984 Historic Property Survey Report for Irvine Center Drive Widening
Paleo - Padon, Beth LSA Associates, Inc.

OR-00841 1986 Archaeological, Historical, and
Paleontological Assessments for Planning
Area 34b, City of Irvine
Scientific Resource
Surveys, Inc.

Paleo - Mason, Roger D.

OR-00847 1985 Archaeological Resource Inventory City of Irvine and its Sphere of Influence
Padon, Beth LSA Associates, Inc. 30-000161, 30-000349, 30-000361, 30-000383, 30-000478, 30-000494,
30-000495, 30-000496, 30-000499,
30-000545, 30-000601, 30-000734,
30-000735, 30-000767, 30-000803,
30-000804, 30-000805, 30-000806,
30-000807, 30-000808
OR-00945 1982 Rossmoor Business Park Liquidating Trust
Properties
Van Horn, David M. Ultra Systems, Inc. 30-000610

Page 1 of 4 ends

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Report List
Report No. Other IDs Year Author(s) Title Affiliation Resources OR-01032 1990 Archaeological Resource Assessment Two
Road Alignments Within Village 34 Lake
Forest Drive and Bake Parkway Orange
County, California
Scientific Resource
Surveys, Inc.

White, Robert S. 30-001110
OR-01109 1986 Addendum to the Historic Property Survey
Report for Irvine Center Drive Widening
Padon, Beth LSA Associates, Inc.

OR-01127 1991 Past to Present: Cultural and Scientific
Resources, an Archival Inventory Irvine
Ranch Open Space Reserve Orange County,
California
Rosenthal, Jane LSA Associates, Inc. 30-000079, 30-000184, 30-000273, 30-000310, 30-000311, 30-000312,
30-000345, 30-000384, 30-000386,
30-000476, 30-000494, 30-000495,
30-000496, 30-000501, 30-000502,
30-000523, 30-000524, 30-000547,
30-000557, 30-000705, 30-000706,
30-000707, 30-000709, 30-000720,
30-000731, 30-000734, 30-000735,
30-000736, 30-000751, 30-000767,
30-000787, 30-000798, 30-000799,
30-000800, 30-000801, 30-000802,
30-000803, 30-000804, 30-000805,
30-000811, 30-000822, 30-000932,
30-000933, 30-000939, 30-000940,
30-000941, 30-000943, 30-000996,
30-000998, 30-001000, 30-001001,
30-001006, 30-001029, 30-001032,
30-001033, 30-001034, 30-001054,
30-001055, 30-001077
Paleo -
OR-01129 1982 Cultural Resource Assessment: the Koll
Property Near Laguna Hills; a Possible
Annexation Area for the City of Irvine and its
Sphere of Influence
Archaeological Associates,
Ltd.

Van Horn, David M. 30-000014, 30-000015, 30-000016,
30-000267, 30-000268, 30-000414,
30-000415, 30-000421, 30-000432,
30-000551, 30-000604, 30-000610,
30-000823, 30-000854, 30-001007
OR-01344 1993 Cultural Resources Element City of Laguna Hills, Orange County, California
Rosenthal, Jane LSA Associates, Inc. 30-000354, 30-000355, 30-000432, 30-000515, 30-000551, 30-000604,
30-000659, 30-000702, 30-000703,
30-000769, 30-000849
OR-02225 1978 The Irvine Company Planning Process and
California Archaeology- A Review and Critique
Other - Irvine Ranch Strozier, Hardy The Irvine Company

Page 2 of 4 ends

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Report List
Report No. Other IDs Year Author(s) Title Affiliation Resources OR-02267 2000 An Archaeological and Paleontological
Survey of the Irvine Spectrum GPA Project
Brian F. Smith and
Associates
Hunt, Kevin P. and Brian
F. Smith
30-000161, 30-000341, 30-000391,
30-000432, 30-000495, 30-000499,
30-000551, 30-000602, 30-000768,
30-000769, 30-000904, 30-001011,
30-001034, 30-001069, 30-001110,
30-100297, 30-100298
Paleo -
OR-02336 2000 Final Report on Archaeological and
Paleontological Monitoring Program
Conducted at Spectrum 5, Irvine, Orange
County, California
Archaeological Resource
Management Corp.

Demcak, Carol R. and
Milos Velechovsky
Paleo -
OR-02406 2001 Review of Cingular Wireless Facility SC 008- 02 Cellular - Duke, Curt LSA Associates, Inc.

OR-02534 1976 Annual Report to The Irvine Company from
Archaeological Research, Inc.

ARI 30-000051, 30-000064, 30-000099,
30-000100, 30-000106, 30-000119,
30-000130, 30-000184, 30-000196,
30-000197, 30-000484, 30-000518,
30-000575
OR-02626 2003 Results of Archaeological Construction
Monitoring Planning Area 27 Needlegrass
Creek Conservation Area, Irvine, California
Younger, Shannon and LSA Associates, Inc.

Smith, Brooks
OR-02639 1998 A Cultural Resources Inventory in Planning Area 18 Irvine, California
Drover, Christopher E. The Keith Companies, Inc. 30-000767, 30-000769, 30-001547 OR-03358 2005 Historical, Archaeological and Paleontological Resources Identification and Evaluation for
the Planning Area 18 Project Including
Impacts Analysis and Mitigation Measures
The Keith Companies,
Jones & Stokes
Archer, Gavin H., Sarah
A. Siren, Lawrence G.

Barnes, Andrew Schmidt,
and Noelle Shaver
30-000769, 30-001547, 30-100390,
30-179839
Paleo -
OR-03467 2006 Cultural Resource Records Search Results
and Site Visit for Cingular
Telecommunications Facility Candidate
OC0175 (Laguna Village HOA) 23441
Avenida Costanero, Laguna Hills, Orange
County, California
Michael Brandman
Associates
Bonner, Wayne H. and
Sarah A. Williams
30-000432, 30-001547
OR-03743 2009 Cultural Resources Investigation for T-Mobile LA02880E "Maxwell" 88 Maxwell, Irvine,
Orange County, California 92618
Archaeological Resources
Technology
Losee, Carolyn
OR-04107 2007 Cultural Resources Field Assessment for the Lake Forest Drive and Bake Parkway
Extensions Project in City of Irvine Planning
Area 34
Archer, Gavin H., David STANTEC
C. Hanna, and Mark R.

Deering

Page 3 of 4 ends

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Report List
Report No. Other IDs Year Author(s) Title Affiliation Resources OR-04289 2012 Archaeological Survey Report Tertiary
Treatment Plant and Recycled Water
Distribution System Expansion Project
Laguna Hills and Laguna Woods, Orange
County, California
Stone, David and Dudek
Victorino, Ken
30-000014, 30-000015, 30-000268

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Primary No. Trinomial
Resource List
Other IDs Type Age Attribute codes Recorded by Reports
P-30-000432 CA-ORA-000432 OR-01011, OR01129, OR-01344, OR-01995, OR02208, OR-02267,
OR-03467
Site Prehistoric AP02 1973 (REEVES, Archaeological
Research, Inc);
1982 (David Van Horn,
Archaeological Associates, ltd)

Page 1 of 1 ends

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Phase I Cultural Resources Report
23161 Mill Creek Project, Laguna Hills, Orange County
Appendix B:

Native American Scoping

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Sacred Lands File & Native American Contacts List Request Native American Heritage Commission
1550 Harbor Blvd, Suite 100
West Sacramento, CA 95691
916-373-3710
916-373-5471 – Fax
[email protected]
Information Below is Required for a Sacred Lands File Search Project: ______________________________________________________________________ County:______________________________________________________________________ USGS Quadrangle Name:_______________________________________________________ Township:__________ Range:__________ Section(s):__________ Company/Firm/Agency:_________________________________________________________ Street Address:________________________________________________________________ City:______________________________________________ Zip:______________________ Phone:_____________________________________________
Fax:_______________________________________________
Email:_____________________________________________
Project Description:

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Latitude: 33.6259973N Longitude: -117.7356113W
Project Site Scale: 1:24,000
23161 Mill Creek Project

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2061 N. Los Robles Avenue, Ste. 205 Pasadena, California 91104 / www.southenvironmental.com December 5, 2024
To all NAHC-listed Tribal Contacts
for the project identified below
RE: 23161 Mill Creek Project, City of Laguna Hills, Orange County, California Dear NAHC Tribal Contact:

South Environmental was retained to conduct a cultural resources inventory for the proposed 23161 Mill Creek Project (proposed project). The project site occupies an approximately 2.43-acre area located at 23161 Mill Creek in the City of Laguna Hills, California. The proposed project site is located on the United States Geological Survey (USGS) San Juan Capistrano, California 7.5-minute Quadrangle Map in Section 29 of Township 06 South and Range 08 West (see enclosed Figure 1). The project proposes to demolish the existing building (constructed in 1987) and develop 43 residential duplexes with attached garages, guest parking, and green space.

As part of the process of identifying potential cultural resources, South Environmental contacted the Native American Heritage Commission (NAHC) and requested a Sacred Lands File search on November 15, 2024. The NAHC responded to the request on December 5, 2024, reporting negative results. The NAHC also provided a list of tribal contacts who may have knowledge of the presence of cultural resources in the vicinity of the proposed project.

If you have any knowledge of cultural resources that may exist within or near the project site, please contact me at [email protected] or 562-900-8816, or via U.S. mail at the address above.

Please note that the request herein is for informational purposes only and does not constitute Assembly Bill 52 notification or initiation of consultation.

Respectfully Submitted,
_______________________
Samantha Jovanovic, MA, MS
Archaeologist
Attachment: Figure 1. Project Location Map

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Latitude: 33.6259973N Longitude: -117.7356113W
Project Site Scale: 1:24,000
23161 Mill Creek Project

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STATE OF CALIFORNIA Gavin Newsom, Governor

NATIVE AMERICAN HERITAGE COMMISSION

Page 1 of 1 ends

December 5, 2024
Samantha Jovanovic
South Environmental, LLC
Via Email to: [email protected]
Re: 23161 Mill Creek Project, Orange County
To Whom It May Concern:

A record search of the Native American Heritage Commission (NAHC) Sacred Lands File (SLF) was completed for the information you have submitted for the above referenced project. The results were negative. However, the absence of specific site information in the SLF does not indicate the absence of cultural resources in any project area. Other sources of cultural resources should also be contacted for information regarding known and recorded sites.

Attached is a list of Native American tribes who may also have knowledge of cultural resources in the project area. This list should provide a starting place in locating areas of potential adverse impact within the proposed project area. I suggest you contact all of those indicated; if they cannot supply information, they might recommend others with specific knowledge. By contacting all those listed, your organization will be better able to respond to claims of failure to consult with the appropriate tribe. If a response has not been received within two weeks of notification, the Commission requests that you follow-up with a telephone call or email to ensure that the project information has been received.

If you receive notification of change of addresses and phone numbers from tribes, please notify me. With your assistance, we can assure that our lists contain current information.

If you have any questions or need additional information, please contact me at my email address: [email protected].

Sincerely,
Andrew Green
Cultural Resources Analyst
Attachment

CHAIRPERSON
Reginald Pagaling
Chumash

VICE-CHAIRPERSON
Buffy McQuillen
Yokayo Pomo, Yuki,
Nomlaki

SECRETARY
Sara Dutschke
Miwok

PARLIAMENTARIAN
Wayne Nelson
Luiseño

COMMISSIONER
Isaac Bojorquez
Ohlone-Costanoan

COMMISSIONER
Stanley Rodriguez
Kumeyaay

COMMISSIONER
Laurena Bolden
Serrano

COMMISSIONER
Reid Milanovich
Cahuilla

COMMISSIONER
Bennae Calac
Pauma-Yuima Band of
Luiseño Indians

ACTING EXECUTIVE

SECRETARY
Steven Quinn

NAHC HEADQUARTERS
1550 Harbor Boulevard
Suite 100
West Sacramento,
California 95691
(916) 373-3710
[email protected]

Page 1198 of 1727 ends

Tribe Name Fed (F)
Non-Fed (N)
Contact Person Contact Address Phone # Fax # Email Address Cultural Affiliation Last Updated Cahuilla Band of Indians F Anthony Madrigal, Tribal Historic Preservation Officer
52701 CA Highway 371
Anza, CA, 92539
(951) 763-5549 [email protected] Cahuilla 6/28/2023 Cahuilla Band of Indians F Erica Schenk, Chairperson 52701 CA Highway 371 Anza, CA, 92539
(951) 590-0942 (951) 763-2808 [email protected] Cahuilla 2/1/2024 Cahuilla Band of Indians F BobbyRay Esparza, Cultural
Director
52701 CA Highway 371
Anza, CA, 92539
(951) 763-5549 [email protected] Cahuilla 6/28/2023 Gabrieleno Band of Mission Indians - Kizh
Nation
N Christina Swindall Martinez,
Secretary
P.O. Box 393
Covina, CA, 91723
(844) 390-0787 [email protected] Gabrieleno 8/18/2023 Gabrieleno Band of Mission Indians - Kizh
Nation
N Andrew Salas, Chairperson P.O. Box 393
Covina, CA, 91723
(844) 390-0787 [email protected] Gabrieleno 8/18/2023 Gabrieleno/Tongva San Gabriel Band of
Mission Indians
N Anthony Morales, Chairperson P.O. Box 693
San Gabriel, CA, 91778
(626) 483-3564 (626) 286-1262 [email protected] Gabrieleno 12/4/2023 Gabrielino Tongva Indians of California
Tribal Council
N Christina Conley, Cultural
Resource Administrator
P.O. Box 941078
Simi Valley, CA, 93094
(626) 407-8761 [email protected]
u
Gabrielino 3/16/2023
Gabrielino Tongva Indians of California
Tribal Council
N Robert Dorame, Chairperson P.O. Box 490
Bellflower, CA, 90707
(562) 761-6417 (562) 761-6417 [email protected] Gabrielino 3/16/2023 Gabrielino/Tongva Nation N Sandonne Goad, Chairperson 106 1/2 Judge John Aiso St., #231
Los Angeles, CA, 90012
(951) 807-0479 [email protected] Gabrielino 3/28/2023 Gabrielino-Tongva Tribe N Charles Alvarez, Chairperson 23454 Vanowen Street West Hills, CA, 91307
(310) 403-6048 [email protected] Gabrielino 5/30/2023 Gabrielino-Tongva Tribe N Sam Dunlap, Cultural Resource Director
P.O. Box 3919
Seal Beach, CA, 90740
(909) 262-9351 [email protected] Gabrielino 5/30/2023 Juaneno Band of Mission Indians N Sonia Johnston, Chairperson P.O. Box 25628 Santa Ana, CA, 92799
[email protected] Juaneno
Juaneno Band of Mission Indians
Acjachemen Nation - Belardes
N Joyce Perry, Cultural Resource
Director
4955 Paseo Segovia
Irvine, CA, 92603
(949) 293-8522 [email protected] Juaneno 3/17/2023
Juaneno Band of Mission Indians
Acjachemen Nation 84A
N Heidi Lucero, Chairperson,
THPO
31411-A La Matanza Street
San Juan Capistrano, CA, 92675
(562) 879-2884 [email protected] Juaneno 3/28/2023 La Jolla Band of Luiseno Indians F Norma Contreras, Chairperson 22000 Highway 76 Pauma Valley, CA, 92061
(760) 742-3771 Luiseno
Pala Band of Mission Indians F Christopher Nejo, Legal
Analyst/Researcher
PMB 50, 35008 Pala Temecula
Road
Pala, CA, 92059
(760) 891-3564 [email protected] Cupeno
Luiseno
11/27/2023
Pala Band of Mission Indians F Alexis Wallick, Assistant THPO PMB 50, 35008 Pala Temecula Road
Pala, CA, 92059
(760) 891-3537 [email protected] Cupeno
Luiseno
11/27/2023
Pala Band of Mission Indians F Shasta Gaughen, Tribal Historic Preservation Officer
PMB 50, 35008 Pala Temecula
Road
Pala, CA, 92059
(760) 891-3515 [email protected] Cupeno
Luiseno
11/27/2023
Pauma Band of Luiseno Indians F Temet Aguilar, Chairperson P.O. Box 369 Pauma Valley, CA, 92061
(760) 742-1289 (760) 742-3422 [email protected] Luiseno Orange,Riverside,San Diego Los Angeles,Orange,Riverside,San
Bernardino,San Diego
Orange,Riverside,San Diego
Orange,Riverside,San Bernardino,San Diego
Orange,Riverside,San Bernardino,San Diego
Orange,Riverside,San Bernardino,San Diego
Los Angeles,Orange,Riverside,San
Bernardino,Santa Barbara,Ventura
Los Angeles,Orange,Riverside,San
Bernardino,Santa Barbara,Ventura
Los Angeles,Orange,Riverside,San
Bernardino,Santa Barbara,Ventura
Orange,Riverside,San Diego
Los Angeles,Orange,Riverside,San
Bernardino,San Diego
Los Angeles,Orange,Riverside,San
Bernardino,Santa Barbara,Ventura
Los Angeles,Orange,Riverside,San
Bernardino,Santa Barbara,Ventura
Los Angeles,Orange,Riverside,San
Bernardino,Santa Barbara,Ventura
Los Angeles,Orange,Riverside,San
Bernardino,Santa Barbara,Ventura
Los Angeles,Orange,Riverside,San
Bernardino,Santa Barbara,Ventura
Native American Heritage Commission
Native American Contact List
Orange County
12/5/2024
Counties
Imperial,Los Angeles,Orange,Riverside,San
Bernardino,San Diego
Imperial,Los Angeles,Orange,Riverside,San
Bernardino,San Diego
Imperial,Los Angeles,Orange,Riverside,San
Bernardino,San Diego
12/05/2024 10:11 AM
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Laguna Hills City CouncilFebruary 10, 2026

Laguna Hills City Council
February 10, 2026