131 Calle Iglesia, Suite 200, San Clemente, CA 92672 (949) 369-6141 www.lgcgeotechnical.com December 2, 2025 Project No. 23106-01
Ms. Crystal Villalpando
Related California
18201 Von Karman Avenue, Suite 900
Irvine, CA 92612
Subject: Updated Preliminary Geotechnical Subsurface Evaluation, Proposed Multi-Family Residential Podium Development, 340 St Ann’s Drive, Laguna Beach, California In accordance with your request, LGC Geotechnical, Inc. is providing an updated preliminary geotechnical subsurface evaluation for the proposed multi-family residential podium development located at 340 St Ann’s Drive in the City of Laguna Beach, California. This report presents the results of our limited subsurface explorations and geotechnical analysis and provides a summary of our conclusions and preliminary recommendations relative to the proposed site development.
Should you have any questions regarding this report, please do not hesitate to contact our office. We appreciate this opportunity to be of service.
Respectfully,
LGC Geotechnical, Inc.
Ryan Douglas, PE, GE 3147 Katie Maes, CEG 2216
Vice President of Engineering Director of Geology
RLD/BTZ/KTM/MDP/amm
Distribution: (1) Addressee (electronic copy)
Attachment 11
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TABLE OF CONTENTS
Section Page
1.0 INTRODUCTION ...................................................................................................................................... 1
1.1 Purpose and Scope of Services ........................................................................................................... 1
1.2 Background ............................................................................................................................................... 1
1.3 Project Description................................................................................................................................. 1
1.4 Subsurface Exploration........................................................................................................................ 4
1.5 Laboratory Testing ................................................................................................................................. 4
2.0 GEOTECHNICAL CONDITIONS............................................................................................................. 6
2.1 Regional Geology .................................................................................................................................... 6
2.1.1 Older Artificial Fill(Map Symbol – afo)............................................................................ 6
2.1.2 Quaternary Terrace Deposits (Map Symbol - Qt)........................................................ 6
2.1.3 Tertiary Topanga Formation(Map Symbol - Tt)......................................................... 6
2.2 Generalized Subsurface Conditions................................................................................................. 7
2.3 Groundwater............................................................................................................................................. 7
2.4 Field Infiltration Testing...................................................................................................................... 7
2.5 Seismic Design Parameters................................................................................................................. 8
2.6 Faulting....................................................................................................................................................... 9
2.6.1 Liquefaction and Dynamic Settlement...........................................................................10
2.6.2 Lateral Spreading ...................................................................................................................10
2.6.3 Tsunamis and Seiches...........................................................................................................11
2.7 Oversized Material................................................................................................................................11
2.8 Expansion Potential..............................................................................................................................11
3.0 CONCLUSIONS........................................................................................................................................12
4.0 RECOMMENDATIONS..........................................................................................................................14
4.1 Site Earthwork .......................................................................................................................................14
4.1.1 Clearing and Grubbing ..........................................................................................................15
4.1.2 Removal and Recompaction Depths and Limits ..........................................................15
4.1.3 Temporary Excavations........................................................................................................16
4.1.4 Removal Bottoms and Subgrade Preparation ..............................................................17
4.1.5 Material for Fill ........................................................................................................................17
4.1.6 Placement and Compaction of Fills...................................................................................18
4.1.7 Trench and Retaining Wall Backfill and Compaction.................................................19
4.1.8 Footing Exavations .................................................................................................................20
4.2 Preliminary Foundation Design Parameters .............................................................................20
4.2.1 Building Structure..................................................................................................................20
4.2.2 Ground Improvement Alternative for Building Structure......................................21
4.2.3 Slab Underlayment Guidliens ............................................................................................21
4.3 Lateral Resistance ................................................................................................................................22
4.4 Lateral Earth Pressures for Basement/Retaining Walls .......................................................22
4.5 Temporary Shoring..............................................................................................................................25 493
TABLE OF CONTENTS (Cont’d)
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4.6 Soil Corrosivity ......................................................................................................................................26
4.7 Preliminary Pavement Recommendations.................................................................................26
4.8 Nonstructural Concrete Flatwork ..................................................................................................27
4.9 Control of Surface Water and Drainage Control.........................................................................28
4.10 Subsurface Water Infiltration..........................................................................................................29
4.11 Pile Shafts for Shoring.........................................................................................................................29
4.12 Pier Shafts for Temporary Shoring................................................................................................29
4.13 Geotechnical Plan Review..................................................................................................................30
4.14 Pre-Construction Monitoring...........................................................................................................30
4.15 Geotechnical Observation and Testing During Construction ................................................30
5.0 LIMITATIONS .........................................................................................................................................31
LIST OF TABLES, ILLUSTRATIONS, & APPENDICES
Tables
Table 1 – Summary of Field Infiltration Testing (Page 8) Table 2 – Seismic Design Parameters (Page 9)
Table 3 – Allowable Soil Bearing Pressures (Page 20)
Table 4A – Lateral Earth Pressures – Cut Condition (Page 23) Table 4B – Lateral Earth Pressures – Conventional Backfilled Retaining Wall (Page 24) Table 5 – Preliminary Asphalt Concrete Paving Section Options (Page 27) Table 6 – Preliminary Geotechnical Parameters for Nonstructural Concrete Flatwork Placed on Very Low to Low Expansion Potential Subgrade (Page 28)
Figures
Figure 1 – Site Location Map (Page 3)
Figure 2 – Geotechnical Map (Site Plan) (Rear of Text)
Figure 3 – Geotechnical Map (Topographic Map) (Rear of Text) Figure 4 – Multi-Period Design Response Spectrum
Figure 5 – Basement Subterranean Structure Backfill/Subdrain Detail (Rear of Text) Figure 6 – Retaining Wall Backfill Detail (Rear of Text) Appendices
Appendix A – References
Appendix B – Boring Logs
Appendix C – Laboratory Test Results
Appendix D – Infiltration Testing Results
Appendix E – General Earthwork and Grading Specifications 494
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1.0 INTRODUCTION
1.1 Purpose and Scope of Services
This updated preliminary geotechnical report is for the proposed multi-family residential podium development located at 340 St Ann’s Drive in the City of Laguna Beach, California (see Site Location Map, Figure 1). The purpose of our work was to evaluate site geotechnical conditions and to provide preliminary geotechnical recommendations with respect to the proposed development.
1.2 Background
Review of historical aerial photographs indicates the site was generally undeveloped during 1945, however Glenneyre Street and cross streets are visible (Historic Aerials, 2023). During 1952, site development occurred and some of the structures including the north half of the exiting church structure and the parsonage residence have been constructed, along with a parking lot. Based on review of background documents, an addition to the church was constructed and the parking lot was re-graded during the 1960’s (Twining Laboratories, 1962).
At that time, the existing concrete retaining walls along the northwestern boundary of the subject property were constructed, with a descending slope to the existing drainage that passes northwest of the site. Based on the referenced report (Soils International, 1978), a portion of the former church property to the northwest of the current site limits was proposed for residential construction, and residences are present there now.
1.3 Project Description
The approximately 1.2-acre site is bound to the northeast by Catalina Street, to the southeast by St Ann’s Drive, to the southwest by Glenneyre Street, and to the northwest by existing residential developments. The site is currently an existing church development with several buildings, a parking lot, and retaining walls situated throughout the site (Architectural Drawings, 2023). The main church building appears to be two levels. The parking lot is asphalt concrete. A daycare play yard and ancillary building are located on the north side of the main church building. An approximately 15-foot-tall retaining wall retains the neighboring residential property and landscape area in the eastern corner of the site adjacent to Catalina Street. An approximately 8- foot-tall retaining wall retains the church building on the southwestern property line adjacent to Glenneyre Street. The site descends to the neighboring residential neighborhood adjacent to the parking lot on the northwestern property line. A concrete retaining wall exists along a portion of the northwestern property line. Topographically the site has variable developed areas with elevations ranging from approximately 66 feet above mean sea level (msl) in the western portion of the site to approximately 84 feet above msl in the southern portion of the site and approximately 90 feet above msl in the eastern corner of the site above the existing retaining wall (T&M Surveying, 2022).
It is our understanding that the proposed development has been updated to consist of a twostory multi-family structure with a podium parking subterranean floor and other appurtenant 495
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improvements. The proposed project excludes the existing church and will remain in place. The subterranean level is anticipated to essentially encompass the entire northern and western portions of the site and consist of 42 parking stalls. The entrance driveway to the subterranean parking will be located on the western side of the site along Glenneyre Street (Related, 2025).
The proposed building footprint is depicted on Figure 2 – Geotechnical Map (Site Plan). The structure is proposed to have two levels above ground and one level below ground (subterranean). The podium structure is anticipated to be reinforced concrete. A preliminary grading plan was not available at the time of this report. Preliminary structural (dead plus live) loads have not been provided at this time. However, we have estimated maximum (dead plus live) column and wall loads of 150 kips and 5 kips/ft, respectively.
The recommendations given in this report are based upon the preliminary proposed layout and estimated structural loading information above. We understand that the project plans are currently being developed at this time; LGC Geotechnical should be provided with updated project plans and the final structural loads when they become available, in order to either confirm or modify the recommendations provided herein. 496
Approximate
Site Location
FIGURE 1
Site Location Map
DATE December 2025
ENG. / GEOL.
PROJECT NO.
PROJECT NAME
SCALE
RLD
Not to Scale
Related - 340 St. Ann's, Laguna Beach
23106-01
497
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1.4 Subsurface Geotechnical Evaluation
A limited geotechnical field evaluation was performed by LGC Geotechnical in June of 2023. This program consisted of drilling and sampling four small-diameter exploratory hollow-stem borings (HS-1 through HS-4) and three hand-auger borings (HA-1 through HA-3) for the purpose of obtaining samples for evaluation and laboratory testing of site soils. Two of the borings (I-1 and I-2) were excavated for infiltration testing.
Four hollow-stem auger borings (HS-1 through HS-4) were drilled by 2R Drilling under subcontract to LGC Geotechnical. The depth of the borings ranged from approximately 25 to 45 feet below existing grade. Boring HS-1 was terminated at a depth of approximately 45 feet below existing grade due to auger refusal. An LGC Geotechnical representative observed the drilling operations, logged the borings, and collected soil samples for laboratory testing. The borings were performed using a truck-mounted drill rig equipped with 6-inch diameter hollow-stem augers. Driven soil samples were collected by means of the Standard Penetration Test (SPT) and Modified California Drive (MCD) sampler generally obtained at 2.5 to 5-foot vertical increments. The MCD is a split-barrel sampler with a tapered cutting tip and lined with a series of 1-inch-tall brass rings. The SPT sampler (1.4-inch ID) and MCD sampler (2.4-inch ID, 3.0-inch OD) were driven using a 140-pound automatic hammer falling 30 inches to advance the sampler a total depth of 18 inches. The raw blow counts for each 6-inch increment of penetration were recorded on the boring logs. Bulk samples of the near-surface soils were also collected and logged at select borings for laboratory testing. In select borings, after removal of the augers the depth of the boring due to caving was measured and is noted on the boring logs.
At the completion of drilling, the borings were backfilled with the native soil cuttings, tamped and the surface was replaced with asphalt cold patch, where necessary. Some settlement of the backfill soils/asphalt cold patch may occur over time.
Infiltration testing was performed within two borings, I-1 and I-2, to depths of approximately 5 feet below existing grade with an 8-inch auger. An LGC Geotechnical engineer installed standpipes, backfilled the borings with crushed rock and pre-soaked the infiltration holes prior to testing. Infiltration testing was performed per the South County of Orange testing guidelines (2017). Standpipes were removed and the locations were subsequently backfilled with native soils at the completion of testing. Some settlement of the backfill soils may occur over time.
Boring logs are presented in Appendix B and their approximate locations are depicted on Figure 3 – Geotechnical Map (Topographic Plan).
1.5 Laboratory Testing
Representative driven and bulk samples were retained for laboratory testing during our field evaluation. Laboratory testing included in-situ unit weight and moisture content, fines content, Atterberg limits, direct shear, consolidation, expansion index, and corrosion (sulfate, chloride, pH, and minimum resistivity).
The following is a summary of the laboratory test results. • Dry density of the samples collected ranged from approximately 99 pounds per cubic foot (pcf) to 119 pcf, with an average of 109 pcf. Field moisture contents ranged from 498
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approximately 3 percent to 29 percent, with an average of 14 percent. • Two fines content tests indicated a fines content (percent passing No. 200 sieve) of 34 and 45 percent. Based on the Unified Soils Classification System (USCS), the tested samples would be classified as “coarse-grained.”
• Two Atterberg Limit (liquid limit and plastic limit) tests were performed. Results indicated Plasticity Index (PI) values of 16 to 18.
• Three direct shear tests were performed. The plots are provided in Appendix C. • Two consolidation tests were performed. The stress vs. deformation plots are provided in Appendix C.
• One Expansion Index (EI) test was performed. Results were an EI of 4, corresponding to “Very Low” expansion potential.
• Corrosion testing indicated soluble sulfate content less than 0.02 percent, chloride content of 41 parts per million (ppm), pH value of 7.5, and minimum resistivity of 1,950 ohm-cm.
A summary of the laboratory test results is presented in Appendix C. 499
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2.0 GEOTECHNICAL CONDITIONS
2.1 Regional Geology
The site is located on the coastal portion of the western border of the Peninsular Ranges Geomorphic Province of California, specifically within the San Joaquin Hills. The San Joaquin Hills are the result of a theoretical uplift along a blind thrust fault at depth below the hills. The hillsides generally consist of Tertiary bedrock formations that have been faulted and uplifted to form the hillside ascending to the northeast of the subject site. The local geology has also been influenced by changes in sea level, resulting in a series of abandoned terrace deposits on wave-cut marine platforms along the coast, generally sub-horizontal. Marine terrace deposits are typically present on the base of wave-cut platforms, and soils eroded over time (non-marine) have been deposited over the marine terrace in some locations. Localized drainages have incised into the terraces and bedrock below, throughout the region.
Our review of readily available geotechnical documents indicates that the subject site is not located within a Seismic Hazard Zone, including areas of earthquake-induced landslides and liquefaction (CDMG, 2006), or a State of California Earthquake Fault Zone (CGS, 2018). No faults were encountered during our investigation and no faults are mapped across the site on the reviewed regional geologic maps.
Per the regional geologic map of the area, the site is underlain by a veneer of Quaternary terrace deposits, over Tertiary Topanga Formation bedrock (USGS, 1957; Edgington & Tan, 1976). The materials are described below.
2.1.1 Older Artificial Fill (Map Symbol - afo)
Older artificial fill soils are present on site that were placed during previous uses and development of the property and the adjacent property to the northwest. As encountered, older artificial fill soils were loose to medium dense, brown mottled clayey and silty sand, and sandy clay.
2.1.2 Quaternary Terrace Deposits (Map Symbol - Qt)
Regional geologic maps indicate Quaternary terrace deposits are present at the site; generally sandwiched between older artificial fill and the underlying bedrock unit.
Terrace deposits are typically formed by deposition of beach sand and coastal erosional deposits onto a subhorizontal, wave-cut platform of bedrock. As encountered, terrace deposits consist of olive brown to brown sandy clay, silty sand, and clayey sand.
2.1.2 Tertiary Topanga Formation (Map Symbol – Tt)
The primary bedrock formation underlying the site is the Tertiary Topanga Formation.
The material is generally described as sandstone with minor siltstone and pebble 500
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conglomerate interbeds, weakly cemented, very dense (Edgington & Tan, 1976). As encountered, the bedrock consisted of grayish brown to brown, very dense silty sandstone, and minor amounts of hard sandy claystone.
2.2 Generalized Subsurface Conditions
The field explorations (borings) generally indicate the site contains up to approximately 15 feet of previously placed undocumented artificial fill over native Terrace Deposits overlying Topanga Formation Bedrock to the maximum explored depth of approximately 45 below existing grade.
Older artificial fill soils encountered were primarily loose to medium dense clayey and silty sands and very stiff sandy clays. Native terrace deposits are primarily stiff to very stiff sandy clays and medium dense to dense silty sands and clayey sands. Bedrock consisted of primarily very dense silty sands and hard sandy clays.
It should be noted that geotechnical explorations are only representative of the location where they are performed, and varying subsurface conditions may exist outside of each location. In addition, subsurface conditions can change over time. The soil descriptions provided above should not be construed to mean that the subsurface profile is uniform, and that soil is homogeneous within the project area. For details on the stratigraphy at the exploration locations, refer to the boring logs provided in Appendix B.
2.3 Groundwater
Groundwater was not encountered in our borings to the maximum explored depth of approximately 45 feet below existing grade. Based on the Seismic Hazard Zone Report for the Laguna Beach Quadrangle (CDMG, 2006), no depth to historic high groundwater is indicated for the site. Please note, however, that a blue-line drainage is depicted as passing just west of the subject site. The nearby drainage from Bluebird Canyon that collects drainage from the ascending hillsides northeast of the subject site, has been channelized into a storm drain alignment that remains in-place northwest of the site, at a lower elevation.
It should be noted that higher localized and seasonal perched groundwater conditions may accumulate below the surface and should be expected throughout the design life of the proposed improvements. In general, groundwater conditions below any given site may vary over time depending on numerous factors including seasonal rainfall, local irrigation, and intentional infiltration of stormwater, among others.
2.4 Field Infiltration Testing
Two field percolation tests were performed in the southern and eastern portions of the site per the direction of the project civil engineer, the locations are depicted on Figure 2 – Geotechnical Map (Site Plan). Test well installation consisted of placing a 3-inch diameter perforated PVC pipe in the excavated 8-inch diameter borehole and backfilling the annulus with crushed rock including the placement of approximately 2 inches of crushed rock at the bottom of the borehole. The infiltration test wells were presoaked the day of installation and testing took 501
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place within 24 hours of presoaking. During the pre-test, the water levels in the borings were observed to drop less than 6 inches in 25 minutes for two consecutive readings. Therefore, the test procedure for fine-grained soils or “slow test” was followed. Test well installation and the estimation of infiltration rates were accomplished in general accordance with the guidelines set forth by South Orange County (2017). In general, three-dimensional flow out of the test well (percolation), as observed in the field, is mathematically reduced to one-dimensional flow out of the bottom of the test well (infiltration). Infiltration tests are performed using relatively clean water, free of particulates, silt, etc. The results of our recent field infiltration testing are presented in Appendix D and summarized in Table 1 below.
TABLE 1
Summary of Field Infiltration Testing
Infiltration Test
Identification
Approx. Depth
Below Existing
Grade (ft)
Observed
Infiltration Rate*
(in./hr.)
I-1 5 0.0
I-2 5 0.2
*Observed Infiltration Rates Do Not Include Factor of Safety.
The tested infiltration rates provided in this report are considered a general representation of the infiltration rates at the location of the proposed infiltration boring. Please note, the testing of infiltration rates is highly dependent upon the materials encountered at the point of testing (i.e., location and depth of testing). Varying subsurface conditions may exist outside of the test location which could alter the calculated infiltration rate. Please refer to Section 4.10 for subsurface water infiltration recommendations.
2.5 Seismic Design Parameters
The site seismic characteristics were evaluated per the guidelines set forth in Chapter 16, Section 1613 of the 2025 California Building Code (CBC) and applicable portions of ASCE 7-22 which has been adopted by the CBC. The code-based Multi-Period Design Response Spectrum (MPDRS) per ASCE 7-22 is provided on Figure 4. The provided MPDRS is an envelope of the applicable site class as indicated below. For each response period, T, less than 10 seconds and not equal to one of the discrete values of period (T) provided on Figure 4, the spectral response acceleration parameter (Sa) shall be determined by linear interpolation between values of Sa.
Refer to Chapter 11 of ASCE 7-22. The structural designer should contact the geotechnical consultant if structural conditions require site-specific ground motions. 502
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TABLE 2
Seismic Design Criteria
Selected Parameters from 2025 CBC,
Section 1613 - Earthquake Loads
Seismic
Design
Criteria
Notes/References
Distance to applicable faults classifies the site as a
“Near-Fault” site. Section 11.4.1 of ASCE 7
Site Latitude 33.537435 Degrees North
Site Longitude -117.777951 Degrees West
Shear Wave Determination, v̅s Estimated* Chapter 20 of ASCE 7 Applicable Site Classes CD, D Chapter 20 of ASCE 7
*Estimated v̅s requires deriving site class by vs/1.3 & 1.3vs, envelope (maximum) presented
A disaggregation of the PGA based on a 2,475-year average return period (MCE) indicates that an earthquake magnitude of 6.73 at a distance of approximately 8.84 km from the site would contribute the most to this ground motion. A disaggregation of the PGA based on a 475-year average return period (Design Earthquake) indicates that an earthquake magnitude of 6.56 at a distance of approximately 20.97 km from the site would contribute the most to this ground motion (USGS, 2018).
Section 1803.5.12 of the 2025 CBC (per Section 11.8.3 of ASCE 7) states that the maximum considered earthquake geometric mean (MCEG) Peak Ground Acceleration (PGA) should be used for liquefaction potential. The PGAM for the site is equal to 0.68g (SEAOC, 2025). The design PGA is equal to 0.45g (2/3 of PGAM).
2.6 Faulting
Prompted by damaging earthquakes in Northern and Southern California, State legislation and policies concerning the classification and land-use criteria associated with faults have been developed. Their purpose was to prevent the construction of urban developments across the trace of active faults. The result is the Alquist-Priolo Earthquake Fault Zoning Act. According to the State Geologist, an active fault is defined as one which has had surface displacement within the Holocene Epoch (roughly the last 11,000 years). A potentially active fault is defined as any fault, which has had surface displacement during Quaternary time (last 1,600,000 years), but not within the Holocene. Earthquake Fault Zones have been delineated along the traces of active faults within California. Where developments for human occupation are proposed within these zones, the state requires detailed fault evaluations be performed so that engineering geologists can mitigate the hazards associated with active faulting by identifying the location of active faults and allowing for a setback from the zone of previous ground rupture.
The subject site is not located within a State of California Earthquake Fault Zone (i.e., AlquistPriolo Earthquake Fault Act Zone) and no active faults are known to cross the site. A fault is 503
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considered “active” if evidence of surface rupture in Holocene time (the last approximately 11,000 years) is present. The possibility of damage due to ground rupture is considered low since no active faults are known to cross the site.
Secondary effects of seismic shaking resulting from large earthquakes on the major faults in the Southern California region, which may affect the site, include ground lurching, shallow ground rupture, soil liquefaction and dynamic settlement. These secondary effects of seismic shaking are a possibility throughout the Southern California region and are dependent on the distance between the site and causative fault and the onsite geology. The closest major active faults that could produce these secondary effects include the Whittier-Elsinore, San Joaquin Hills Blind Thrust, Newport Inglewood, San Andreas Fault Zones, among others. The closest major active fault to the site is the San Joaquin Hills Blind Thrust Fault located at depth below the site (no surface rupture). A discussion of these secondary effects is provided in the following sections.
2.6.1 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 coexist: 1) shallow groundwater; 2) low density noncohesive (granular) soils; and 3) high-intensity ground motion. Studies indicate that loose, saturated, near surface cohesionless soils exhibit the highest liquefaction potential, while dry, dense, cohesionless soils and cohesive soils exhibit low to negligible liquefaction potential. In general, cohesive soils are not considered susceptible to liquefaction (Bray & Sancio, 2006). Effects of liquefaction on level ground include settlement, sand boils, and bearing capacity failures below structures. Dynamic settlement of dry sands can occur as the sand particles tend to settle and densify as a result of a seismic event.
The site is not located within a State of California Seismic Hazard Zone for liquefaction potential (CDMG, 1998). Based on the lack of a shallow groundwater table at the site, relatively shallow depth to formational materials, and the generally dense nature of the material below the site, there is a very low potential for liquefaction.
2.6.2 Lateral Spreading
Lateral spreading is a type of liquefaction induced ground failure associated with the lateral displacement of surficial blocks of sediment resulting from liquefaction in a subsurface layer. Once liquefaction transforms the subsurface layer into a fluid mass, gravity plus the earthquake inertial forces may cause the mass to move downslope towards a free face (such as a river channel or an embankment). Lateral spreading may cause large horizontal displacements and such movement typically damages pipelines, utilities, bridges, and structures.
Due to the lack of groundwater in the upper 50 feet and very low potential for liquefaction, the potential for lateral spreading is considered very low. 504
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2.6.3 Tsunamis and Seiches
Based on the subject site elevation, there is a low possibility of damage to the site during a large tsunami event. The site is not located within the Tsunami Inundation Area delineated on the Tsunami Hazard Area Map for the Laguna Beach Quadrangle (CGS, 2021).
2.7 Oversized Material
Oversized material (material larger than 8 inches in maximum dimension) may be encountered during site grading. Recommendations are provided for appropriate handling of oversized materials in Appendix E. If feasible, crushing oversized materials onsite or exporting oversized materials may be considered. Incorporating oversized materials into “rock fills” (windrows, rock blankets or individual rock burial) may be feasible in some of the deeper remedial grading areas if applicable. Special handling recommendations should be provided on a case-by-case basis, if necessary.
2.8 Expansion Potential
Based on the results of our laboratory testing, site soils have a “Very Low” to “Low” expansion potential. Final expansion potential of site soils should be determined at the completion of grading. Results of expansion testing at finish grades will be utilized to confirm final foundation design.
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3.0 CONCLUSIONS
Based on the results of our subsurface evaluation and understanding of the proposed development, it is our opinion that the proposed development is feasible from a geotechnical standpoint. A summary of our conclusions are as follows:
• Based on our subsurface evaluation and review of regional geologic maps and published geotechnical literature, the site contains up to approximately 15 feet of previously placed undocumented artificial fill over native Terrace Deposits overlying Topanga Formation bedrock to the maximum explored depth of approximately 45 below existing grade. Older artificial fill soils encountered were primarily loose to medium dense clayey and silty sands and very stiff sandy clays. Native terrace deposits are primarily stiff to very stiff sandy clays and medium dense to dense silty sands and clayey sands. Bedrock consisted of primarily very dense silty sands (sandstone) and hard sandy clays.
• The previously placed artificial fill soils and near-surface soils are generally loose and are not suitable for the planned improvements in their present condition (refer to Section 4.1); removal and recompaction will be required. An alternative to performing deeper removals of existing artificial fill soils is ground improvement likely consisting of Rammed Aggregate Piers (RAP). • Groundwater was not encountered in our borings to the maximum explored depth of approximately 45 feet below existing grade. Based on the Seismic Hazard Zone Report for the Laguna Beach Quadrangle (CDMG, 2006), no depth to historic high groundwater is indicated for the site.
• The site is not located within a State of California Seismic Hazard Zone for liquefaction potential (CDMG, 1998). The potential for liquefaction is considered very low due to the lack of a groundwater table, relatively shallow formational materials, and generally dense nature of the material below the site.
• The proposed development will likely be subjected to strong seismic ground shaking during its design life. The site is not located within a State of California Earthquake Fault Zone (i.e., AlquistPriolo Earthquake Fault Act Zone) and no active faults are known to cross the site. • Due to the proximity of the proposed improvements to the property line in portions of the site, temporary shoring and/or “A-B-C” slot cuts may be required to achieve required earthwork removal and recompaction. The temporary shoring will be adjacent to an existing off-site structure in a portion of the site.
• Based on the results of preliminary laboratory testing, site soils are anticipated to have “Very Low” to “Low” expansion potential. Final design expansion potential must be determined at the completion of grading.
• Field testing resulted in infiltration rate of essentially zero and 0.2 inches per hour in Infiltration Borings I-1 and I-2, respectively. Site consists primarily of fine-grained (i.e., silts and clays) soils which have very low permeability and therefore have very low infiltration rates. • The site contains soils that are not suitable for basement/retaining wall backfill due to their fines (i.e., silt and clay) content, therefore or import of sandy soils will be required by the contractor for obtaining suitable backfill soil for planned site basement/retaining walls. 506
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• Based on the corrosion test results, soils are not considered corrosive per the Caltrans criteria (Caltrans, 2021).
• Excavations into the existing site soils should be feasible with heavy construction equipment in good working order. We anticipate that the sandy and silty earth materials generated from the excavations will be generally suitable for re-use as compacted fill, provided they are relatively free of rocks larger than 8 inches in dimension, construction debris, and significant organic material. 507
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4.0 RECOMMENDATIONS
The following recommendations are to be considered preliminary and should be confirmed upon completion of grading and earthwork operations. In addition, they should be considered minimal from a geotechnical viewpoint, as there may be more restrictive requirements from the architect, structural engineer, building codes, governing agencies, or the owner.
It should be noted that the following geotechnical recommendations are intended to provide the owner with sufficient information to develop the site in general accordance with the 2025 California Building Code (CBC) requirements. With regard to the potential occurrence of potentially catastrophic geotechnical hazards such as fault rupture, earthquake-induced landslides, liquefaction, etc. the following geotechnical recommendations should provide adequate protection for the proposed development to the extent required to reduce seismic risk to an “acceptable level.” The “acceptable level” of risk is defined by the California Code of Regulations as “that level that provides reasonable protection of the public safety, though it does not necessarily ensure continued structural integrity and functionality of the project” [Section 3721(a)]. Therefore, repair and remedial work of the proposed structures may be required after a significant seismic event. With regards to the potential for less significant geologic hazards to the proposed development, the recommendations contained herein are intended as a reasonable protection against the potential damaging effects of geotechnical phenomena such as expansive soils, soil settlement, groundwater seepage, etc. It should be understood, however, that our recommendations are intended to maintain the structural integrity of the proposed development and structures given the site geotechnical conditions but cannot preclude the potential for some cosmetic distress or nuisance issues to develop as a result of the site geotechnical conditions.
The geotechnical recommendations contained herein must be confirmed to be suitable or modified based on the actual as-graded conditions.
4.1 Site Earthwork
We anticipate that earthwork will generally consist of demolition of existing improvements and buildings, shoring installation, required removal and recompaction, subgrade preparation, precise grading and construction of the proposed new improvements including the podium structure, site buildings, site amenities, courtyards, subsurface utilities, driveways, etc.
We recommend that earthwork onsite be performed in accordance with the following recommendations, future geotechnical reports, the 2025 CBC/City of Laguna Beach requirements and the General Earthwork and Grading Specifications included in Appendix E. In case of conflict, the following recommendations shall supersede those included in Appendix E. The following recommendations should be considered preliminary and may be revised based upon future evaluation and our review of updated project plans and/or the field conditions exposed during site grading/construction.
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4.1.1 Clearing and Grubbing
Prior to earthwork of areas to receive structural fill, engineered structures or improvements, the areas should be cleared of existing vegetation, building structures, pavement, utilities, surface obstructions, existing debris and potentially compressible or otherwise unsuitable material. Vegetation and debris should be removed and properly disposed of off-site. Holes resulting from the removal of buried obstructions, which extend below proposed removal bottoms, should be replaced with properly compacted fill material. Any abandoned sewer or storm drain lines should be completely removed and replaced with properly placed compacted fill. Deeper demolition may be required in order to remove existing foundations. We recommend the trenches associated with demolition which extend below the remedial grading depth be backfilled and properly compacted prior to the demolition contractor leaving the site.
If cesspools or septic systems are encountered during earthwork, they should be removed in their entirety. The resulting excavation should be backfilled with properly compacted fill soils. As an alternative, cesspools can be backfilled with lean sand-cement slurry. At the conclusion of the clearing operations, a representative of LGC Geotechnical should observe and accept the site prior to further earthwork.
4.1.2 Removal and Recompaction Depths and Limits
In order to provide a relatively uniform bearing condition for the planned building structures and improvements we recommend the site soils be removed and recompacted. Subsurface site soils should be removed and/or over-excavated according to the criteria outlined below.
Based on the site conditions and proposed building structure, we have provided recommendations for two different earthwork/foundation design options, see below.
Option 1 – Removal of Older Artificial Fill: For Option 1, Existing artificial fill within the influence of the proposed structural improvements should be removed to suitable, competent native materials prior to placement of artificial fill to design grades. For areas with shallow competent native soils below the bottom of the proposed building, minimum overexcavation should be 4 feet below finish pad grade or 2 feet below bottom of the footings, whichever is deeper. Depth of existing fill is shown on Figure 2 & Figure 3.
Option 2 –Ground Improvement: For Option 2, the entire building structure will be supported on ground improvement such as Rammed Aggregate Piers (RAP) eliminating the requirement for deep removals. For the ground improvement option, the upper 1 foot below finish pad grade should be removed and recompacted with properly placed compacted fill.
Please refer to the encountered geologic descriptions and depths presented on the boring logs (Appendix B) and on the Geotechnical Map (Topographical Plan) (Figure 3). 509
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Where adequate space is available, the base of removal bottoms should extend laterally a minimum distance equal to the depth of removal and recompaction below finish grade. Specifically, soils located within a 1:1 (horizontal to vertical) projection of the bottom of footings must be compacted fill or competent natural ground. Building lines may be defined as the perimeter of the building proper, plus attached or adjacent foundation supported features, including canopies, elevators, or walls.
Local conditions may be encountered which could require additional removal and recompaction beyond the above-noted minimum to obtain an acceptable subgrade. The actual depths and lateral extents of removal and recompaction should be determined by the geotechnical consultant based on the subsurface conditions encountered during grading. Removal and recompaction areas and areas should be accurately staked in the field by the Project Surveyor.
4.1.3 Temporary Excavations
Temporary excavations up to approximately 10 to 20 feet are anticipated. Temporary 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. Based on our field investigation, the majority of site soils are anticipated to be OSHA Type “B” soils (refer to the attached boring logs). Sandy soils are present and should be considered susceptible to caving. Raveling of the sandy soils should be anticipated for temporary slopes. Flatter slope inclinations should be considered if raveling cannot be tolerated. The exposed slope surface may be kept surficially moist (but not saturated) during construction to reduce (not eliminate) potential sloughing. Soil conditions should be regularly evaluated during construction 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 consultant should be maintained to facilitate construction while providing safe excavations. Excavation safety is the sole responsibility of the contractor.
The potential for impacting the existing improvements and adjacent properties may be reduced by performing excavations using narrow “A-B-C” slot cuts. “A-B-C” slot cuts are defined as excavations perpendicular to sensitive property boundaries that are divided into multiple “slots” of equal width. If slots are labeled A, B, C, A, B, C, etc., then “A” slots should be excavated at the same time but must be backfilled before “B” slots can be excavated, etc. For preliminary planning purposes, slot cuts should be no wider than 8 feet and no deeper than 8 feet. Slot cuts are not recommended where proposed excavations are adjacent to existing building structures (and within 5 horizontal feet), Slot cuts should be backfilled immediately with properly placed compacted fill (per Section 4.1.6) to finish grade prior to excavation of adjacent slots. Due to the presence of sands at the site which are susceptible to caving, narrower slot cuts may be required.
These preliminary recommendations should be further evaluated based on the proposed grading plan. Protection of the existing improvements during grading is the responsibility of the contractor.
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Surcharge loads (vehicular traffic, soil stockpiles, construction equipment, etc.) should be set back from the perimeter of excavations a minimum distance equivalent to a 1:1 projection from the bottom of the excavation or 5 feet, whichever is greater, unless the cut is properly shored and designed for the applicable surcharge load. Once an excavation has been initiated, it should be backfilled as soon as practical. Prolonged exposure of temporary excavations may result in some localized instability. Excavations should be planned so that they are not initiated without sufficient time to shore/fill them prior to weekends, holidays, or forecasted rain.
It should be noted that any excavation that extends below a 1:1 (horizontal to vertical) projection of an existing foundation will remove existing support of the structure foundation. Temporary shoring recommendations are provided in Section 4.5.
4.1.4 Removal Bottoms and Subgrade Preparation
In general, removal bottoms and areas to receive compacted fill should be scarified to a minimum depth of 6 inches, brought to a near-optimum moisture condition (generally within optimum and 2 percent above optimum moisture content), and re-compacted per project recommendations.
Removal bottoms and areas to receive fill should be observed and accepted by the geotechnical consultant prior to subsequent fill placement. Soil subgrade for planned footings and improvements (e.g., slabs, etc.) should be firm and competent.
4.1.5 Material for Fill
From a geotechnical perspective, the onsite soils are generally suitable for use as general compacted fill, provided they are screened of oversized material (8 inches in greatest dimension), construction debris and significant organic materials.
From a geotechnical viewpoint, any required import soils for general fill (i.e., nonretaining wall backfill) should consist of soils of granular soils of “Very Low” expansion potential (expansion index 20 or less based on American Society for Testing and Materials [ASTM] D 4829), and free of organic materials, construction debris and any material greater than 3 inches in maximum dimension. Import for any required retaining wall backfill should meet the criteria outlined in the following paragraph. Source samples should be provided to the geotechnical consultant for laboratory testing a minimum of four working days prior to any planned importation.
Basement/retaining wall backfill should consist of imported or onsite clean granular (sandy) soils with a maximum of 35 percent fines (passing the No. 200 sieve) per American Society for Testing and Materials (ASTM) D1140 (or ASTM D6913/ASTM D422) and a “Very Low” expansion potential (EI of 20 or less per ASTM D4829). Soils should also be screened of organic materials, construction debris, and any material greater than 3 inches in maximum dimension. Some of the onsite soils are expansive and have high fines content and are not suitable for backfill of site retaining walls. 511
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Therefore, select grading and stockpiling of the onsite soils or import or soils meeting the criteria outlined above should be anticipated by the contractor for obtaining suitable retaining wall backfill soil. These preliminary findings should be confirmed during grading.
Aggregate base (crushed aggregate base or crushed miscellaneous base) should conform to the requirements of Section 200-2 of the Standard Specifications for Public Works Construction (“Green Book”) for untreated base materials (except processed miscellaneous base), Caltrans Class 2 aggregate base or the City of Laguna Beach requirements.
The placement of demolition materials in compacted fill is acceptable from a geotechnical viewpoint provided the demolition material is broken up into pieces not larger than typically used for aggregate base (approximately 1 to 3-inches in maximum dimension) and well blended into fill soils with essentially no resulting voids. Demolition material placed in fills must be free of construction debris (wood, brick, etc.) and reinforcing steel.
If asphalt concrete fragments will be incorporated into the demolition materials, approval from an environmental viewpoint may be required and is not the purview of the geotechnical consultant. From our previous experience, we recommend that asphalt concrete fragments be limited to fill areas within planned drive aisles and courtyards (i.e., not within building pad areas).
4.1.6 Placement and Compaction of Fills
Material to be placed as fill should be brought to near-optimum moisture content (generally within optimum and 2 percent above optimum moisture content) and recompacted to at least 90 percent relative compaction (per ASTM D1557). Moisture conditioning of site soils will be required in order to achieve adequate compaction. Drying and or mixing of very moist soils may be required prior to reusing the materials in compacted fills. In general, the site soils will require additional moisture in order to achieve the required compaction.
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 not exceeding 8 inches in compacted thickness. Each lift should be thoroughly compacted and accepted prior to subsequent lifts. Generally, placement and compaction of fill should be performed in accordance with the local grading ordinances with observation and testing performed by the geotechnical consultant. Oversized material as previously defined should be removed from site fills.
During backfill of excavations, the fill should be properly benched into firm and competent soils of temporary backcut slopes as it is placed in lifts.
Aggregate base material should be compacted to a minimum of 95 percent relative compaction at or slightly above optimum moisture content per ASTM D1557. Subgrade below aggregate base should be compacted to a minimum of 90 percent relative compaction per ASTM D1557 at near-optimum moisture content (generally within 512
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optimum and 2 percent above optimum moisture content).
If gap-graded ¾-inch rock is used for backfill (around storm drain storage chambers, retaining wall backfill, etc.) it will require compaction. Rock shall be placed in thin lifts (typically not exceeding 6 inches) and mechanically compacted with observation by geotechnical consultant. Backfill rock shall meet the requirements of ASTM D2321. Gapgraded rock is required to be wrapped in filter fabric to prevent the migration of fines into the rock backfill.
4.1.7 Trench and Retaining Wall Backfill and Compaction Bedding material used within the pipe zone should conform to the requirements of the current Greenbook and the pipe manufacturer. Where applicable, sand having a sand equivalent (SE) of 30 or greater (per Caltrans Test Method [CTM] 217) may be used to bed and shade the pipes within the bedding zone. Sand backfill should be densified by jetting or flooding and then tamped to ensure adequate compaction. Bedding sand should be from a natural source, manufactured sand from recycled material is not suitable for jetting. The onsite soils may generally be considered suitable as trench backfill (zone defined as 12 inches above the pipe to subgrade), provided the soils are screened of rocks greater than 6 inches in maximum dimension, construction debris and organic material.
Trench backfill should be compacted in uniform lifts (as outlined in Section “Material for Fill”) by mechanical means to at least 90 percent relative compaction (per ASTM D1557).
If gap-graded rock is used for trench backfill, refer to Section 4.1.6.
Utility trenches running parallel to footings should not be excavated within a 1:1 (horizontal to vertical) downward projection from adjacent footings (“footing influence zone”) to avoid potential undermining. Depending on the utility line and structural loading of the footing, utility trenches running perpendicular to footings may require special provisions such as sand-cement slurry backfill of the utility trench in this zone or flexible sleeves through the footings. These conditions should be evaluated on a case-bycase basis.
Retaining wall backfill should consist of sandy soils as defined in the above section “Material for Fill.” For subterranean/basement walls the select sandy zone should extend a minimum of a 1:1 (horizontal to vertical) upward projection from the bottom of the basement wall subdrain, refer to Figure 3. For conventional retaining walls the limits of select sandy backfill should extend at minimum ½ the height of the retaining wall or the width of the heel (if applicable), whichever is greater, refer to Figure 4. Retaining wall backfill soils should be compacted in relatively uniform thin lifts to at least 90 percent relative compaction (per ASTM D1557). Jetting or flooding of retaining wall backfill materials should not be permitted.
In backfill areas where mechanical compaction of soil backfill is impractical due to space constraints, typically sand-cement slurry may be substituted for compacted backfill. The slurry should generally contain about one sack of cement per cubic yard. When set, such a mix typically has the consistency of compacted soil. Sand cement slurry placed near the 513
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surface within landscape areas should be evaluated for potential impacts on planned improvements.
A representative from LGC Geotechnical should observe, probe, and test backfill to verify compliance with the project recommendations.
4.1.8 Footing Excavations
Footing excavation bottoms should be firm, relatively unyielding, and free of loose material. Footing excavations should be observed and accepted by the geotechnical consultant prior to placement of steel reinforcement. Footing excavations in sandy soils left open and allowed to dry will be susceptible to caving.
4.2 Preliminary Foundation Design Parameters
Preliminary foundation recommendations are provided below. Please note that the following foundation recommendations are preliminary and must be confirmed by LGC Geotechnical at the completion of project plans (i.e., foundation, grading and site layout plans) as well as completion of earthwork. Lateral resistance is provided in Section 4.3.
4.2.1 Building Structure
Provided our earthwork removal and recompaction recommendations are implemented, and older artificial fill is removed to competent native materials, the proposed structure may be supported on a shallow foundation system. The following minimum footing widths and embedments are recommended for the corresponding allowable bearing pressures for both continuous wall and column spread footings.
TABLE 3
Allowable Soil Bearing Pressures
Allowable Static
Bearing Pressure
(psf)
Minimum Footing
Width
(feet)
Minimum Footing
Embedment*
(feet)
3,500 3 2
3,000 2 2
2,500 1.5 1.5
* Refers to minimum depth measured below lowest adjacent grade.
These net bearing pressures (exclusive of the weight of the footings) are for dead plus live loads and may be increased one-third for short-term, transient, wind and seismic 514
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loading. The maximum edge pressures induced by eccentric loading or overturning moments should not be allowed to exceed these recommended values. For any bearing pressures less than 2,500 psf, a minimum footing width of 1 feet and embedment depth of 1 feet below lowest adjacent grade should be used. These allowable bearing pressures are applicable for level (ground slope equal to or flatter than 5 horizontal feet to 1-foot vertical) conditions only.
Soil settlement is a function of footing dimensions and applied soil bearing pressure.
Based on the recommended earthwork removals and estimated structural loads, foundation settlement due to structural loads (static settlement) is anticipated to be on the order of 1-inch. Differential settlement should be anticipated between nearby columns or walls where a large differential loading condition exists. Settlement estimates should be evaluated by LGC Geotechnical when foundation plans are made available.
4.2.2 Ground Improvement Alternative for Building Structure An alternative to performing deep removals below the building structure footprint is a ground improvement technique such as Rammed Aggregate Piers (RAP). Rammed aggregate piers (RAP) consist of drilled holes filled with aggregate that is mechanically compacted as it is placed. A proprietary foundation support system such as Geopiers may be feasible for support of planned structure. Advantages of this system would significantly reduce recommended earthwork removal and recompaction depths below the structure, increase soil bearing pressure, and reduce the long-term (static) settlement. Because such systems are proprietary, the work is performed on a designbuild basis by the specialty contractor. Every aspect of the design and construction of the ground improvement system is the responsibility of the specialty contractor/designer including estimated settlements of foundations bearing on the RAPs.
It is standard of practice for the geotechnical consultant to observe the construction of the ground improvement system (e.g., RAPs, etc.) to confirm that they have been installed in accordance with the approved foundation plan. A representative of LGC Geotechnical can perform these services including confirmation of the diameter of the drilled hole, specified lift thickness and compaction effort. The locations of the RAPs should be confirmed by the project surveyor.
4.2.3 Slab Underlayment Guidelines
The following is for informational purposes only since slab underlayment (e.g., moisture retarder, sand or gravel layers for concrete curing and/or capillary break) is unrelated to the geotechnical performance of the foundation and thereby not the purview of the geotechnical consultant. Post-construction moisture migration should be expected below the foundation. The foundation engineer/architect should determine whether the use of a capillary break (sand or gravel layer), in conjunction with the vapor retarder, is necessary or required by code. Sand layer thickness and location (above and/or below 515
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vapor retarder) should also be determined by the foundation engineer/architect.
4.3 Lateral Resistance
Resistance to lateral loads can be provided by friction acting at the base of foundations and by passive earth pressure. For concrete/soil frictional resistance, an allowable coefficient of friction of 0.30 may be assumed with dead-load forces. An allowable passive lateral earth pressure of 240 pcf to a maximum of 2,400 pcf may be used for lateral resistance for properly compacted fill and suitable native soils. This allowable passive pressure may be increased to 325 pcf to a maximum of 3,250 pcf for short-duration wind or seismic loading. For isolated pole footings (e.g., sign structures, decks, etc.) generally spaced a minimum of 3 pile diameters oncenter, an allowable passive pressure of 480 pcf may be used for passive resistance. The provided passive pressure is based on an arching factor of 2 (e.g., 240 pcf x 2) and should be limited to a maximum of 10 times the value provided above (e.g., 480 pcf to a maximum of 4,800 psf). This value may be increased by one-third for short-duration wind or seismic loading. These passive pressure values are applicable for level (ground slope equal to or flatter than 5H:1V) conditions only. Frictional resistance and passive pressure may be used in combination without reduction. The provided allowable passive pressure includes a static and seismic factor of safety of 1.5 and 1.1, respectively. This increase is based on a reduced factor of safety for short duration loading.
4.4 Lateral Earth Pressures for Basement/Retaining Walls It is our understanding that basement walls up to approximately 20 feet will be required for the subterranean parking level. In addition, internal retaining walls for an access ramp may be required. Lateral earth pressures are provided as equivalent fluid unit weights, in pound per square foot (psf) per foot of depth or pcf. These values do not contain an appreciable factor of safety, so the retaining wall designer should apply the applicable factors of safety and/or load factors during design. A soil unit weight of 120 pcf may be assumed for calculating the actual weight of soil over the wall footing. At this time level backfill conditions are anticipated. If a sloping backfill condition is proposed, increased lateral earth pressures will be provided based on the planned configuration.
If the retaining wall can yield enough to mobilize the full shear strength of the soil, it can be designed for “active” pressure. If the wall cannot yield under the applied load, the earth pressure will be higher. This would include 90-degree corners of retaining walls. Such walls should be designed for “at-rest.” The equivalent fluid pressure values assume free-draining conditions and a drainage system will be installed and maintained to prevent the build-up of hydrostatic pressures. Typically, a basement wall constructed against the temporary shoring is provided with a composite drainage mat (e.g., Miradrain, etc.) placed over the lagging and collected at the wall bottom by a manifold pipe system properly outletted to a suitable discharge point. Backfilled retaining walls are backfilled with sandy soils and a subdrain pipe is wrapped in drainage aggregate and filter fabric (e.g., “burrito” subdrain) and properly outletted to a suitable discharge point (Refer to Figures 5 and 6). If a sump pump is required to outlet accumulated water behind retaining/basement walls, the owner and any subsequent owners must be made aware that it will be their responsibility to ensure the sump pump continues to perform properly for the life of 516
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the project. Basement/retaining wall structures should be provided with appropriate drainage and appropriately waterproofed. Please note that waterproofing and specification of the drainage mat and outlet system are not the purview of the geotechnical consultant. 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 consultant.
The following lateral earth pressures are presented on Table 4A for design of site basement/retaining walls constructed against the shoring wall (i.e., cut condition not requiring select sandy backfill).
TABLE 4A
Lateral Earth Pressures – Cut Condition
Conditions
Equivalent Fluid Weight (pcf)
Level Backfill
Cut Condition w/Shoring Wall
Active 45
At Rest 70
The following lateral earth pressures are presented on Table 4B are for conventional backfilled retaining walls using approved select granular soils with a maximum of 35 percent fines (passing the No. 200 sieve per ASTM D-421/422) and a maximum Expansion Index of 20 (per ASTM D4829). Some of the onsite soils are expansive and have high fines content and are not suitable for backfill of site retaining walls. Therefore, select grading and stockpiling of the onsite soils or import or soils meeting the criteria outlined above should be anticipated by the contractor for obtaining suitable retaining wall backfill soil. The retaining wall designer should clearly indicate on the retaining wall plans the required sandy soil backfill criteria. If the limits of select sandy backfill indicated on Figures 5 and 6 cannot be extended due to property line constraints, the lateral earth pressures provided in Table 4A should be used. 517
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TABLE 4B
Lateral Earth Pressures – Conventional Backfilled
Retaining Wall
Conditions
Equivalent Fluid Weight (pcf)
Level Backfill – Sand Backfill
Approved Backfill Material
Active 35
At Rest 55
Surcharge loading effects from any adjacent structures should be evaluated by the basement/retaining wall designer. In general, structural loads within a 1:1 (horizontal to vertical) upward projection from the bottom of the proposed basement/retaining wall footing will surcharge the proposed retaining structure. In addition to the recommended earth pressure, basement/retaining walls adjacent to streets should be designed to resist vehicular traffic if applicable. Uniform surcharges may be estimated using the applicable coefficient of lateral earth pressure using a rectangular distribution. A factor of 0.33 and 0.5 may be used for the active and at-rest conditions, respectively. The vertical traffic surcharge may be determined by the structural designer. The retaining/basement wall designer should contact the geotechnical consultant for any required geotechnical input in estimating any applicable surcharge loads.
If required, the basement/retaining wall designer may use a seismic lateral earth pressure increment of 10 pcf for a level backfill. This increment should be applied in addition to the provided static lateral earth pressure using a triangular distribution with the resultant acting at H/3 in relation to the base of the retaining structure (where H is the retained height). Per Section 1803.5.12 of the 2025 CBC, the seismic lateral earth pressure is applicable to structures assigned to Seismic Design Category D through F for retaining wall structures supporting more than 6 feet of backfill height. For the restrained, at-rest condition, the seismic increment may be added to the applicable active lateral earth pressure (in lieu of the at-rest lateral earth pressure) when analyzing short duration seismic loading. It should be noted that the provided seismic lateral earth pressures are for a maximum basement/retaining wall of 20 feet in height and level backfill. While not anticipated at this time, if a basement/retaining wall greater than 20 feet in height is proposed and/or a sloping backfill condition, the retaining wall designer should contact the geotechnical consultant for specific seismic lateral earth pressure increments based on the configuration of the planned retaining wall structures. Seismic lateral earth pressures are estimated using the procedure outlined by the Structural Engineers Association of California (Lew, et al, 2010) and the Federal Highway Administration (FHWA, 2011).
Soil bearing and lateral resistance (friction coefficient and passive resistance) are provided in Sections 4.2.1 and 4.3, respectively. Earthwork considerations (temporary backcuts, backfill, compaction, etc.) for retaining walls are provided in Section 4.1 (Site Earthwork) and the subsequent earthwork related sub-sections.
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4.5 Temporary Shoring
Temporary shoring will likely be required for construction of basement walls adjacent to property lines. Due to the height of the proposed excavation, bracing will likely be required in portions of the site. If the earthwork option is chosen instead of the ground improvement option, temporary shoring must incorporate heights for required remedial grading. The earth pressures provided below are only for temporary shoring conditions, for permanent retaining structures, refer to Section 4.4.
Typical cantilever temporary shoring, where deflection of the shoring will not impact the performance of adjacent structures, with a level backfill may be designed using the active equivalent fluid pressures of 35 pounds per square foot (psf) per foot of depth (or pcf). Braced shoring may be used in areas where the shoring will be located close to existing structures in order to limit shoring defections or required due to the proposed depth of excavation. Braced shoring with a level backfill without hydrostatic pressures (above groundwater) may be designed using a uniform soil pressure of 24H in pounds per square foot (psf), where H is equal to the depth in feet of the excavation being shored. Any slopes above temporary shoring will increase the above-noted lateral earth pressures and can be provided on a case-by-case basis.
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. Refer to the surcharge loading effects discussion provided in above Section 4.4. The shoring designer should contact the geotechnical engineer for any required geotechnical input in estimating any applicable lateral surcharge loads.
Continuous lagging should be provided between the soldier piles. Lagging should be placed in a timely manner during excavation in order to minimize potential spalling and sloughing. Careful installation of the lagging will be necessary to achieve bearing against the retained earth. The backfill of the lagging should consist of sand-cement slurry. Means and methods are per the contractor in order to ultimately ensure full bearing (direct contact) of retained earth to the lagging. The soldier piles should be designed for the full anticipated lateral earth pressure; however, the pressure on the lagging will be less due to soil arching between the piles. We recommend that the lagging be designed for the recommended earth pressure but may be limited to a maximum value of 400 psf if surcharge loads are not present. Lagging placed behind the solider piles will negate the soil arching effect.
For temporary shoring piles generally spaced a minimum of 2.5 pile diameters on-center, an allowable passive pressure of 550 pcf may be used for passive resistance. The provided passive pressure is based on an arching factor of 2 (e.g., 275 pcf x 2) and should be limited to a maximum of 10 times the value provided above (e.g., 550 pcf to a maximum of 5,500 psf). The passive pressure is only applicable for level (5 horizontal feet to 1-foot vertical or flatter) soil conditions. To develop the full lateral value, provisions should be made to assure firm contact between the soldier piles and the undisturbed soils. The concrete placed in the soldier pile excavation below the excavated level should be of adequate strength to transfer the imposed loads to the surrounding soils. Structural designer should incorporate appropriate factor of safety and/or load factor in design. The provided allowable passive pressure is based on a factor of safety of 1.3.
For a deadman footing a minimum of 1-foot below lowest adjacent grade (measured from the 519
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top of the inclined footing) and a width of 4 feet inclined at 45 degrees, an allowable soil bearing of 3,000 psf may be used. To reduce the movement of the shoring, the rakers should be tightly wedged against the footings and/or shoring system.
It is difficult to accurately predict the amount of deflection of the shored mass. It should be realized, however, that some deflection will occur. The shoring should be designed to limit deflection to within tolerable limits. If greater deflection occurs during construction, additional bracing may be necessary. In areas where less deflection is desired, such as adjacent to existing settlement sensitive improvements, the shoring should be designed for higher lateral earth pressures.
The contractor should evaluate the potential drilling conditions when planning the installation methods, refer to Section 4.11.
4.6 Soil Corrosivity
Although not corrosion engineers (LGC Geotechnical is not a corrosion consultant), several governing agencies in Southern California require the geotechnical consultant to determine the corrosion potential of soils to buried concrete and metal facilities. We therefore present the results of our testing with regard to corrosion for the use of the client and other consultants, as they determine necessary.
Corrosion testing indicated soluble sulfate content less than 0.02 percent, chloride content of 41 parts per million (ppm), pH value of 7.5, and minimum resistivity of 1,950 ohm-cm. Based on Caltrans Corrosion Guidelines (2021), soils are considered corrosive if the pH is 5.5 or less, or the chloride concentration is 500 ppm or greater, or the sulfate concentration is 1,500 ppm (0.15 percent) or greater. Based on the test results, soils are not considered corrosive using Caltrans criteria.
Based on laboratory sulfate test results, the near surface soils are designated to a class “S0” per ACI 318, Table 19.3.1.1 with respect to sulfates. Concrete in direct contact with the onsite soils can be designed according to ACI 318, Table 19.3.2.1 using the “S0” sulfate classification.
Laboratory testing may need to be performed at the completion of grading by the project corrosion engineer to further evaluate the as-graded soil corrosivity characteristics.
Accordingly, revision of the corrosion potential may be needed, should future test results differ substantially from the conditions reported herein. The client and/or other members of the development team should consider this during the design and planning phase of the project and formulate an appropriate course of action.
4.7 Preliminary Pavement Recommendations
The following preliminary minimum asphalt concrete (AC) pavement sections provided in Table 5 are based on a preliminary assumed R-value of 25 for Traffic Indices of 5.0 (or less) and 6.0.
These recommendations must be confirmed with R-value testing of representative near-surface soils at the completion of earthwork and after underground utilities have been installed and 520
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backfilled. Final street sections should be confirmed by the project civil engineer based upon the final design Traffic Index. If requested, additional sections may be provided based on other provided traffic index values. Should the City of Laguna Beach have more stringent requirements, updated pavement recommendations can be provided.
TABLE 5
Preliminary Asphalt Concrete Paving Section Options
Assumed Traffic Index 5.0 (or less) 6.0
Estimated R -Value Subgrade 25 25
AC Thickness 4.0 inches 4.5 inches
Aggregate Base Thickness 5.0 inches 7.0 inches
The pavement section thicknesses provided above are considered minimum thicknesses.
Increasing the thickness of any or all of the above layers will reduce the likelihood of the pavement experiencing distress during its service life. The above recommendations are based on the assumption that proper maintenance and irrigation of the areas adjacent to the pavement will occur through the design life of the pavement. Failure to maintain a proper maintenance and/or irrigation program may jeopardize the integrity of the pavement.
Earthwork recommendations regarding aggregate base and subgrade are provided in the previous Section 4.1 “Site Earthwork” and the related sub-sections of this report.
4.8 Nonstructural Concrete Flatwork
Nonstructural concrete flatwork (such as sidewalks, patios/entryways etc.) has a potential for cracking due to changes in soil volume related to soil-moisture fluctuations. To reduce the potential for excessive cracking and lifting, concrete should be designed in accordance with the minimum guidelines outlined in Table 6 on the following page. These guidelines will reduce the potential for irregular cracking and promote cracking along construction joints but will not eliminate all cracking or lifting. Thickening the concrete and/or adding additional reinforcement will further reduce cosmetic distress.
521
Project No. 23106-01 Page 28 December 2, 2025
TABLE 6
Preliminary Geotechnical Parameters for Nonstructural Concrete Flatwork Placed on Very Low to Low Expansion Potential Subgrade
Sidewalks Patios/Courtyards City Sidewalk
Curb and Gutters
Minimum
Thickness (in.) 4 (full) 4 (full) City/Agency Standard
Presoaking Wet down prior to
placing
Wet down prior to
placing
City/Agency
Standard
Reinforcement No. 3 at 24 inches on
centers
City/Agency
Standard
Thickened Edge
(in.) City/Agency Standard
Crack Control
Joints
Saw cut or deep
open tool joint to a
minimum of 1/3 the
concrete thickness
Saw cut or deep
open tool joint to a
minimum of 1/3 the
concrete thickness
City/Agency
Standard
Maximum Joint
Spacing 5 feet 6 feet City/Agency Standard
Aggregate Base
Thickness (in.) City/Agency Standard
4.9 Control of Surface Water and Drainage Control
From a geotechnical perspective, we recommend that compacted finished grade soils adjacent to proposed structures be sloped away from the proposed structure and towards an approved drainage device or unobstructed swale. Drainage swales, wherever feasible, should not be constructed within 5 feet of buildings. Where lot and building, geometry necessitates that the drainage swales be routed closer than 5 feet to structural foundations, we recommend the use of area drains together with drainage swales. Drainage swales used in conjunction with area drains should be designed by the project civil engineer so that a properly constructed and maintained system will prevent ponding within 5 feet of the foundation. Code compliance of grades is not the purview of the geotechnical consultant.
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.
522
Project No. 23106-01 Page 29 December 2, 2025
4.10 Subsurface Water Infiltration
Recent regulatory changes have occurred that mandate that storm water be infiltrated below grade rather than collected in a conventional storm drain system. Typically, a combination of methods are implemented to reduce surface water runoff and increase infiltration including; permeable pavements/pavers for roadways and walkways, directing surface water runoff to grass-lined swales, retention areas, and/or drywells, etc.
It should be noted that collecting and concentrating surface water for the purpose of intentionally infiltrating it below grade, conflicts with the geotechnical engineering objective of directing surface water away from slopes, structures and other improvements. The geotechnical stability and integrity of a site is reliant upon appropriately handling surface water. In general, the vast majority of geotechnical distress issues are directly related to improper drainage. In general, distress in the form of movement of improvements could occur as a result of soil saturation and loss of soil support, expansion, internal soil erosion, collapse and/or settlement.
Based on the very poor results of the infiltration testing, low permeability of the onsite soils, our knowledge of the site geologic conditions, and the relatively shallow depth of very dense formational materials, infiltration of stormwater is not feasible. Therefore, we do not recommend that surface stormwater be intentionally infiltrated into the subsurface soils at this site.
4.11 Pile Shafts for Shoring
Soldier pile boreholes for temporary and permanent shoring should be plumb and free of loose or softened material. Extreme care in drilling, placement of steel, and the pouring of concrete will be essential to avoid excessive disturbance of borehole walls. The soldier pile steel section should be installed, and the concrete pumped immediately after drilling is completed. If applicable, concrete placement by pumping or tremie tube to the bottom of drill hole excavations is recommended. No soldier pile borehole should be left open overnight. We recommend that pile borings not be drilled immediately adjacent to another pile until the concrete in the other pile has attained its initial set. A representative from LGC Geotechnical should be onsite during the drilling of soldier pile boreholes to verify the assumptions made during the design stages.
Sandy soils are present at the site and these materials are generally susceptible to caving. Some caving of drilled holes should be anticipated. The contractor should anticipate that any borehole left open for any extended period of time will likely experience additional caving and possible seepage, typically from local irrigation. Refer to the boring logs in Appendix B. If caving occurs during construction of soldier pile boreholes a temporary casing may be required.
4.12 Supplemental Geotechnical Explorations
It would be prudent to perform additional geotechnical explorations (i.e., borings) to further refine the limits and depth of previously placed artificial fill. 523
Project No. 23106-01 Page 30 December 2, 2025
4.13 Geotechnical Plan Review
Project plans (grading, foundation, retaining wall, temporary shoring, etc.) should be reviewed by this office prior to construction to verify that our geotechnical recommendations have been incorporated. Additional fieldwork and/or modified geotechnical recommendations may be necessary.
4.14 Pre-Construction Monitoring
Due to the proximity of the existing offsite improvements, recommended depth of remedial grading in portions of the site, and proposed retaining walls near the property lines, it is highly recommended that a program of pre-construction documentation and monitoring be devised and put into practice before the onset of any groundwork.
LGC Geotechnical can perform these services at your request. This should include, but not necessarily be limited to, detailed documentation of the existing improvements, walls, buildings, and utilities around the area of proposed excavation, with particular attention to any distress that is already present prior to the start of work. Subsequent readings should be scheduled consistent with the program of work. If shoring systems are to be constructed, routine monitoring of horizontal and vertical movement should be performed for the shoring system and adjacent improvements during construction to verify that shoring deflections are within tolerable limits.
4.15 Geotechnical Observation and Testing During Construction 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 Geotechnical. Geotechnical observation and testing is required per Section 1705 of the 2025 CBC.
Geotechnical observation and/or testing should be performed by LGC Geotechnical at the following stages:
• During grading (removal bottoms, fill placement, etc.); • During drilling of pier shafts for temporary shoring (if any); • During installation of ground improvements such as Geopiers (if any); • During basement/retaining wall backfill and compaction; • During utility trench backfill and compaction;
• After presoaking building pads and other concrete-flatwork subgrades, and prior to placement of aggregate base or concrete;
• After footing excavation and prior to placing concrete and/or reinforcement; • Preparation of pavement subgrade and placement of aggregate base; and • When any unusual soil conditions are encountered during any construction operation subsequent to issuance of this report.
524
Project No. 23106-01 Page 31 December 2, 2025
5.0 LIMITATIONS
Our services were performed using the degree of care and skill ordinarily exercised, under similar circumstances, by reputable soils 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.
This report is based on data obtained from limited observations of the site, which have been extrapolated to characterize the site. While the scope of services performed is considered suitable to adequately characterize the site geotechnical conditions relative to the proposed development, no practical evaluation can completely eliminate uncertainty regarding the anticipated geotechnical conditions in connection with a subject site. Variations may exist and conditions not observed or described in this report may be encountered during construction.
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 other consultants and incorporated into the plans. The contractor should properly implement the recommendations during construction and notify the owner if they consider any of the recommendations presented herein to be unsafe, or unsuitable.
The findings of this report are valid as of the present date. However, changes in the conditions of a site 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. The findings, conclusions, and recommendations presented in this report can be relied upon only if LGC Geotechnical has the opportunity to observe the subsurface conditions during grading and construction of the project, in order to confirm that our preliminary findings are representative for the site. This report is intended exclusively for use by the client, any use of or reliance on this report by a third party shall be at such party’s sole risk.
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. Therefore, this report is subject to review and modification.
525
Figure 2 - Geotechnical Map
(Site Plan) ENG.
PROJECT NO.
PROJECT NAME
SCALE
DATE
Not to Scale
December 2025
Related - 340 St. Ann's, Laguna Beach
RLD / KTM
23106-01 LGC Geotechnical, Inc.
131 Calle Iglesia, Ste. 200
San Clemente, CA 92672
TEL (949) 369-6141 FAX (949) 369-6142
526
HS-3
HS-4
HS-2
HS-1
HA-3
HA-1
HA-2
I-2
I-1
T.D. = 26.5'
afo to 10'
Qt to T.D.
T.D. = 5'
T.D. = 5'
T.D. = 5'
T.D. = 7'
T.D. = 5'
T.D. = 31'
afo to 15'
Qt to 20'
Tt to T.D.
T.D. = 25.5'
afo to 5'
Qt to 20'
Tt to T.D.
T.D. = 45'
afo to 7.5'
Qt to 20'
Tt to T.D.
afo
afo
afo
Qt
Tt
Qt
Tt
LEGEND
Older Artificial Fill
Quaternary Terrace (Non-Marine and Marine,
Undifferentiated), Circled Where Buried
Tertiary Topanga Formation, Circled Where Buried
Approximate Location of Hollow Stem Auger Boring
by LGC Geotechnical, With Total Depth in Feet
Approximate Location of Hand Auger Boring by LGC
Geotechnical, With Total Depth in Feet
Approximate Location of Hollow Stem Auger
Infiltration Boring by LGC Geotechnical, With Total
Depth in Feet
Approximate Limits of This Report
HS-4
HA-3
I-2
afo
Qt
Tt
Figure 3 - Geotechnical Map
(Topographic Plan) ENG.
PROJECT NO.
PROJECT NAME
SCALE
DATE
1" = 40'
December 2025
Related - 340 St. Ann's, Laguna Beach
RLD / KTM
23106-01 LGC Geotechnical, Inc.
131 Calle Iglesia, Ste. 200
San Clemente, CA 92672
TEL (949) 369-6141 FAX (949) 369-6142
527
Period (s) Spectral Acceleration (g)
0 0.50
0.01 0.50
0.02 0.51
0.03 0.53
0.05 0.63
0.075 0.79
0.1 0.93
0.15 1.10
0.2 1.19
0.25 1.23
0.3 1.24
0.4 1.22
0.5 1.16
0.75 0.93
1 0.77
1.5 0.54
2 0.40
3 0.25
4 0.18
5 0.13
7.5 0.078
10 0.053
Applicable Site Classes: CD D Latitude: 33.537435
Envelope Presented Longitude: -117.777951
Reference: ASCE 7-22
Project No. 23106-01 Date: December, 2025
Figure 4:
Multi-Period Design
Response Spectrum
0.0 0.2
0.4 0.6
0.8 1.0
1.2 1.4
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 Spectral Acceleration (g) Period (sec.)
Envelope of Applicable Site Classes
5% Damping
528
Minimum 4" Diameter Schedule 40
Perforated PVC Pipe to Flow to Drainage
Device or Sump Pump per Project Civil
Engineer
Proposed Building Structure by Others
Backcut/Shoring per OSHA
1:1 (H:V) or flatter slope
Earthwork Per Soils Report, Slab Underlay Per
Foundation Engineer/Architect
Compacted Native Soil Cap
Select Granular Backfill (Expansion Index £ 20, maximum 35% fines) Minimum 90% Relative Compaction (ASTM D1557)
NOTE : Granular backfill may be substituted with 3/4 inch crushed compacted rock wrapped in filter fabric.
Geotechnical drainage detail will not prevent water seepage into structure, it is only to prevent build up of water pressure against wall.
EXTENT OF SELECT BACKFILL ZONE
Minimum 1 Cubic Foot Per Linear Foot Burrito Type
Subdrain, Consisting of 3
4 Inch Crushed Rock Wrapped
in Mirafi 140N or Approved Equivalent
1 foot min.
Common Backfill
Minimum 90% Relative Compaction (ASTM D1557)
Waterproofing by Waterproofing
Engineer/Architect or Design
Engineer to be Protected During
Backfill by Contractor
(12" Minimum / 18" Maximum)
1 foot min.
1 1
FIGURE 5
Basement Subterranean
Structure Backfill/Subdrain
Detail
DATE December 2025
ENG. / GEOL.
PROJECT NO.
PROJECT NAME
SCALE
RLD / KTM
Not to Scale
Related - 340 St. Ann's, Laguna Beach
23106-01
529
4 INCH DIAMETER, SCHEDULE 40 PERFORATED
PVC PIPE TO FLOW TO DRAINAGE DEVICE PER
PROJECT CIVIL ENGINEER
COMPACTED SAND BACKFILL
(EXPANSION INDEX £ 20,
MAXIMUM 35% FINES)
NATIVE BACKFILL COMPACTED
PER REPORT
MINIMUM 1 CUBIC FOOT PER LINEAR FOOT
BURRITO TYPE SUBDRAIN, CONSISTING OF
3/4 INCH CRUSHED ROCK WRAPPED IN
MIRAFI 140N OR APPROVED EQUIVALENT
FOOTING/WALL PER DESIGN ENGINEER
WATER PROOFING PER DESIGN ENGINEER
12" MINIMUM
18" MAXIMUM
BACKCUT PER OSHA
EXTENT OF REQUIRED IMPORTED SAND BACKFILL, MINIMUM
HEEL WIDTH OR H/2 WHICH EVER IS GREATER WALL HEIGHT, H
NOTE:
PLACEMENT OF SUBDRAIN
AT BASE OF WALL WILL NOT
PREVENT SATURATION OF SOILS
BELOW AND / OR IN FRONT OF WALL
FIGURE 6
Retaining Wall
Backfill Detail
DATE December 2025
ENG. / GEOL.
PROJECT NO.
PROJECT NAME
SCALE
RLD
Not to Scale
Related - 340 St. Ann's, Laguna Beach
23106-01
530
Appendix A
References
531
Project No. 23106-01 A-1 December 2, 2025
APPENDIX A
References
American Society of Civil Engineers (ASCE), 2022, Minimum Design Loads and Associated Criteria for Buildings and Other Structures, ASCE/SEI 7-22, 2022.
American Society for Testing and Materials (ASTM), 2025, Annual Book of ASTM Standards, Volume
04.08 Soil and Rock (I): D420 – D5876.
Architectural Drawings, 2023, Architectural Plans, Family Apartments and Spiritual Center, Laguna Beach California, dated January 24, 2023.
Bray, J.D., and Sancio, R. B., 2006, Assessment of Liquefaction Susceptibility of Fine-Grained Soils, Journal of Geotechnical and Geoenvironmental Engineering, ASCE, pp. 1165-1177, dated September 2006.
California Building Standards Commission, 2025, California Building Code, California Code of Regulations Title 24, Volumes 1 and 2, dated July 2025.
California Department of Transportation (Caltrans), 2021, Corrosion Guidelines, Version 3.2, dated May 2021.
California Division of Mines and Geology (CDMG), 1998, Earthquake Zones of Required Investigation, Laguna Beach Quadrangle, Official Map Released April 15, 1998. ________, 2006, Seismic Hazard Zone Report for Laguna Beach 7.5 Minute Quadrangle, Orange County California, Hazard Zone Report 013, 2001, updated January 13, 2006.
California Geological Survey (CGS), 2008, Special Publication 117A: Guidelines for Evaluating and Mitigating Seismic Hazards in California.
________, 2018, Earthquake Fault Zones, Special Publication 42, Revised 2018. ________, 2021, Tsunami Hazard Area Map, Laguna Beach Quadrangle, Orange County, California, Scale 1:24,000, dated 2021.
Edginton W.J. & Tan S.S., 1976, Geology of the Laguna Beach Quadrangle, Orange County, California, Special Report 127, dated 1976
Federal Highway Administration (FHWA), 2011, LRFD Seismic Analysis and Design of Transportation Geotechnical Features and Structural Foundation, Reference Manual, Publication No. FHWA11-032, August, 2011.
Historic Aerials, 2023, Historic Aerials photographs from 1938 to 2020, from https://www/historicaerials.com, viewed July 2023,
532
APPENDIX A (Cont’d)
References
Project No. 23106-01 A-2 December 2, 2025
Lew, et al, 2010, Seismic Earth Pressures on Deep Basements, Structural Engineers Association of California (SEAOC) Convention Proceedings.
Related, 2025, Zoning Plan Check Submittal, Building Plan – Podium, NCC Affordable Housing, 340 St Ann’s Drive, Laguna Beach, California, dated October 14, 2025.
Soils International Corporation, 1978, Preliminary Soils and Geologic Report, Church Property, Lot 21, Tract 870, Cleo and Catalina Streets, Project: S-0338-FG, Laguna Beach, California, dated June 9, 1978.
Structural Engineers Association of California (SEAOC), 2025, Seismic Design Maps, Retrieved November 25, 2025, from https://seismicmaps.org/
T&M Surveying, 2022, ALTA/NSPS Land Title Survey, 340 St Ann’s Drive, City of Laguna Beach, County of Orange, State of California, dated November 22, 2022.
Twining Laboratories, 1962, Congregational Church Parking Lot on Catalina between St. Anns Drive and Cleo Street, Laguna Beach, California, Project No. 340A-62-2327, dated October 29, 1962 United States Geological Survey (USGS), 1957, Geologic Map of the San Juan Hills, San Juan Capistrano Area, Orange County California Oil and Gas Investigation Map OM193, dated 1957. ________, 2004, Preliminary Digital Geologic Map of the Santa Ana 30’x60’ Quadrangle, Southern California, Version 2.0, Open File Report 99-172, Prepared in Cooperation with the California Geological Survey; Compiled by D.M. Morton.
________, 2018, Hazard Disaggregation, NSHM Conterminous U.S. 2018, Retrieved November 25, 2025, from https://earthquake.usgs.gov/hazards/interactive/
533
Appendix B
Boring and CPT Logs
534
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 CONDITIONS ENCOUNTERED. THE DESCRIPTIONS
PROVIDED ARE QUALITATIVE FIELD DESCRIPTIONS
AND ARE NOT BASED ON QUANTITATIVE
ENGINEERING ANALYSIS. CN CONSOLIDATION
CR CORROSION
AL ATTERBERG LIMITS CO COLLAPSE/SWELL RV R-VALUE
-#200 % PASSING # 200 SIEVE
DIRECT SHEAR MAXIMUM DENSITY
SIEVE ANALYSIS
SIEVE AND HYDROMETER
EXPANSION INDEX
TEST TYPES: DSMD
SA
S&H
EI
SAMPLE TYPES: B BULK SAMPLE R RING SAMPLE (CA Modified Sampler) G GRAB SAMPLE
SPT STANDARD PENETRATION
TEST SAMPLE GROUNDWATER TABLE
30 25
20 15
10 5
0 Elevation (ft) Depth (ft) Graphic Log Sample Number Blow Count Dry Density (pcf) Moisture (%) USCS Symbol DESCRIPTION Type of Test Hole Diameter:
Hole Location: See Geotechnical Map
Drop:
Type of Rig:
Project Number:
Elevation of Top of Hole: Drive Weight:
Drilling Company:
Project Name:
Date:
70 65
60 55
50 Geotechnical Boring Log Borehole HS-1
6/20/2023
~74' MSL
6"
Truck Mounted Rig
30"
140 pounds
2R Drilling
Woodhart LLC- Laguna Beach
23106-01
Logged By JMN
Sampled By JMN
Checked By RLD
@ 0' - 3" Asphalt Concrete over 3.5" Aggregate Base
R-1 2
2 4
107.3 14.9 SC @ 5' - Clayey SAND: brown, very moist, loose R-2 3
3 3
109.4 13.1 @ 7.5' - Clayey SAND: brown, very moist, loose R-3 3
6 10
112.7 16.3 CL @ 10' - Sandy CLAY: dark olive brown, moist, stiff AL CN
SPT-1 3
3 6
16.3 @ 15' - Sandy CLAY: brown, moist, stiff
R-4 19
50/5" 108.7 16.6 SM @ 20' - Silty SAND: grayish brown, very moist, very dense
SPT-2 29
50/5" 17.9 @ 25' -Silty SAND : light gray, very moist, very dense B-1 Last Edited: 6/26/2023 45 @ 0' to 7.5' - Artificial Fill by Others (afo)
@ 7.5' to 20' - Quaternary Terrace Deposits (Qt)
@ 20' to T.D. - Topanga Formation (Tt)
535
60 TEST TYPES: DSMD
SA
S&H
EI DIRECT SHEAR MAXIMUM DENSITY
SIEVE ANALYSIS
SIEVE AND HYDROMETER
EXPANSION INDEX
55 50
45 40
35 Elevation (ft) Depth (ft) Graphic Log Sample Number Blow Count Dry Density (pcf) Moisture (%) USCS Symbol DESCRIPTION Type of Test Date:
Project Name:
Project Number:
Elevation of Top of Hole:
Hole Location: See Geotechnical Map
Drilling Company:
Type of Rig:
Drop:
Drive Weight:
Hole Diameter:
30 CN CONSOLIDATION
CR CORROSION
AL ATTERBERG LIMITS CO COLLAPSE/SWELL RV R-VALUE
-#200 % PASSING # 200 SIEVE
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 CONDITIONS ENCOUNTERED. THE DESCRIPTIONS
PROVIDED ARE QUALITATIVE FIELD DESCRIPTIONS
AND ARE NOT BASED ON QUANTITATIVE
ENGINEERING ANALYSIS.
SAMPLE TYPES: B BULK SAMPLE R RING SAMPLE (CA Modified Sampler) G GRAB SAMPLE
SPT STANDARD PENETRATION
TEST SAMPLE GROUNDWATER TABLE
40 35
30 25
20 Geotechnical Boring Log Borehole HS-1
6/20/2023
~74' MSL
6"
Truck Mounted Rig
30"
140 pounds
2R Drilling
Woodhart LLC- Laguna Beach
23106-01
Logged By JMN
Sampled By JMN
Checked By RLD
R-5 50/5" 104.1 13.0 ML @ 30' - Sandy SILT: gray, moist, hard SPT-3 27
50/4" 29.4 SM @ 35' - Silty SAND: gray, wet, very dense R-6 50/1" 109.3 17.6 CL @ 40' - Sandy CLAY: gray, moist, hard SPT-4 50/1" 9.9 @ 45' - Sandy CLAY: gray, moist, hard
Total Depth = 45' (Auger Refusal)
Groundwater Not Encountered
Caving: Hole Measured approximately 22' after Removal
of the Augers
Backfilled with Cuttings and Capped with AC Cold Patch
on 6/20/2023
536
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 CONDITIONS ENCOUNTERED. THE DESCRIPTIONS
PROVIDED ARE QUALITATIVE FIELD DESCRIPTIONS
AND ARE NOT BASED ON QUANTITATIVE
ENGINEERING ANALYSIS. CN CONSOLIDATION
CR CORROSION
AL ATTERBERG LIMITS CO COLLAPSE/SWELL RV R-VALUE
-#200 % PASSING # 200 SIEVE
DIRECT SHEAR MAXIMUM DENSITY
SIEVE ANALYSIS
SIEVE AND HYDROMETER
EXPANSION INDEX
TEST TYPES: DSMD
SA
S&H
EI
SAMPLE TYPES: B BULK SAMPLE R RING SAMPLE (CA Modified Sampler) G GRAB SAMPLE
SPT STANDARD PENETRATION
TEST SAMPLE GROUNDWATER TABLE
30 25
20 15
10 5
0 Elevation (ft) Depth (ft) Graphic Log Sample Number Blow Count Dry Density (pcf) Moisture (%) USCS Symbol DESCRIPTION Type of Test Hole Diameter:
Hole Location: See Geotechnical Map
Drop:
Type of Rig:
Project Number:
Elevation of Top of Hole: Drive Weight:
Drilling Company:
Project Name:
Date:
70 65
60 55
50 Geotechnical Boring Log Borehole HS-2
6/20/2023
~75' MSL
6"
Truck Mounted Rig
30"
140 pounds
2R Drilling
Woodhart LLC- Laguna Beach
23106-01
Logged By JMN
Sampled By JMN
Checked By RLD
@ 0' - 1" Asphalt Concrete over 2" Aggregate Base
R-1 10
12 15
117.1 13.2 SC @ 5' - Clayey SAND: brown, moist, medium dense R-2 3
6 16
114.1 14.4 CL @ 7.5' - Sandy CLAY: olive, moist, very stiff R-3 7
14 19
114.8 15.0 @ 10' - Sandy CLAY: brown, moist, very stiff DS
R-4 12
14 18
115.3 15.2 @ 15' - Sandy CLAY: brown, moist, very stiff SPT-1 16
23 50/5"
18.9 SM @ 20' - Silty SAND: olive brown, wet, very dense R-5 50/5" 110.8 15.0 @ 25' - Silty SAND: olive gray, very moist, very dense Total Depth = 25.5'
Groundwater Not Encountered
Caving: Hole measured approximately 11' after Removal
of the Augers
Backfilled with Cuttings and Capped with AC Cold Patch
on 6/20/2023 B-1 Last Edited: 6/26/2023
@ 0' to 5' - Artificial Fill by Others (afo)
@ 5' to 20' - Quaternary Terrace Deposits (Qt)
@ 20' to T.D - Topanga Formation (Tt)
537
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 CONDITIONS ENCOUNTERED. THE DESCRIPTIONS
PROVIDED ARE QUALITATIVE FIELD DESCRIPTIONS
AND ARE NOT BASED ON QUANTITATIVE
ENGINEERING ANALYSIS. CN CONSOLIDATION
CR CORROSION
AL ATTERBERG LIMITS CO COLLAPSE/SWELL RV R-VALUE
-#200 % PASSING # 200 SIEVE
DIRECT SHEAR MAXIMUM DENSITY
SIEVE ANALYSIS
SIEVE AND HYDROMETER
EXPANSION INDEX
TEST TYPES: DSMD
SA
S&H
EI
SAMPLE TYPES: B BULK SAMPLE R RING SAMPLE (CA Modified Sampler) G GRAB SAMPLE
SPT STANDARD PENETRATION
TEST SAMPLE GROUNDWATER TABLE
30 25
20 15
10 5
0 Elevation (ft) Depth (ft) Graphic Log Sample Number Blow Count Dry Density (pcf) Moisture (%) USCS Symbol DESCRIPTION Type of Test Hole Diameter:
Hole Location: See Geotechnical Map
Drop:
Type of Rig:
Project Number:
Elevation of Top of Hole: Drive Weight:
Drilling Company:
Project Name:
Date:
62 57
52 47
42 Geotechnical Boring Log Borehole HS-3
6/20/2023
67' MSL
6"
Truck Mounted Rig
30"
140 pounds
2R Drilling
Woodhart LLC- Laguna Beach
23106-01
Logged By JMN
Sampled By JMN
Checked By RLD
@ 0' - 3.5" Asphalt Concrete with no Aggregate Base -#200 MD
CR
EI
DS
R-1 3
7 17
104.4 10.1 SM @ 5' - Silty SAND: dark brown, moist, medium dense R-2 5
5 9
107.9 8.1 SM @ 7.5' - Silty SAND: yellowish brown, moist, medium dense
R-3 7
10 13
109.8 13.5 CL @ 10' - CLAY with Sand: olive, moist, very stiff AL CN
SPT-1 4
4 8
15.6 SC @ 15' - Clayey SAND: brown, moist, medium dense, after 15' water added to assist with drilling process
R-4 4
7 7
119.4 2.9 SM @ 20' - Silty SAND: yellowish brown, moist, medium dense
SPT-2 2
3 4
25.4 CL @ 25' - Sandy CLAY: brown, moist, stiff
Total Depth = 26.5'
Groundwater Not Encountered
Caving: Hole measured approximately 11.5' after Removal of the Augers
Backfilled with Cuttings and Capped with AC Cold Patch on 6/20/2023 B-1 Last Edited: 6/26/2023
@ 0' to 10' - Artificial Fill by Others (afo)
@ 10' to T.D. - Quaternary Terrace Deposits (Qt)
SC Clayey SAND: dark olive gray
538
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 CONDITIONS ENCOUNTERED. THE DESCRIPTIONS
PROVIDED ARE QUALITATIVE FIELD DESCRIPTIONS
AND ARE NOT BASED ON QUANTITATIVE
ENGINEERING ANALYSIS. CN CONSOLIDATION
CR CORROSION
AL ATTERBERG LIMITS CO COLLAPSE/SWELL RV R-VALUE
-#200 % PASSING # 200 SIEVE
DIRECT SHEAR MAXIMUM DENSITY
SIEVE ANALYSIS
SIEVE AND HYDROMETER
EXPANSION INDEX
TEST TYPES: DSMD
SA
S&H
EI
SAMPLE TYPES: B BULK SAMPLE R RING SAMPLE (CA Modified Sampler) G GRAB SAMPLE
SPT STANDARD PENETRATION
TEST SAMPLE GROUNDWATER TABLE
30 25
20 15
10 5
0 Elevation (ft) Depth (ft) Graphic Log Sample Number Blow Count Dry Density (pcf) Moisture (%) USCS Symbol DESCRIPTION Type of Test Hole Diameter:
Hole Location: See Geotechnical Map
Drop:
Type of Rig:
Project Number:
Elevation of Top of Hole: Drive Weight:
Drilling Company:
Project Name:
Date:
64 59
54 49
44 Geotechnical Boring Log Borehole HS-4
6/20/2023
69' MSL
6"
Truck Mounted Rig
30"
140 pounds
2R Drilling
Woodhart LLC- Laguna Beach
23106-01
Logged By JMN
Sampled By JMN
Checked By RLD
@ 0' - 3" of AC over 3" AB
R-1 8
7 8
99.0 8.2 SC @ 5' - Clayey SAND: light brown, moist, medium dense R-2 7
10 12
112.6 10.8 SC @ 7.5' - Clayey SAND: light brown, moist, medium dense
R-3 8
9 13
99.8 16.5 CL @ 10' - Sandy CLAY: olive brown, moist, very stiff R-4 3
6 6
108.5 11.6 SM @ 15' - Silty SAND: brown, moist, loose -#200 CO
SPT-1 23
41 37
23.4 SM @ 20' - Silty SAND: gray, moist, very dense, oxidation R-5 35
50/4" 102.8 18.9 SM @ 25' - Silty SAND: olive gray, moist, very dense, signs of oxidation B-1 Last Edited: 6/26/2023
@ 0' to 15' - Artificial Fill by Others (afo)
@ 15' to 20' - Quaternary Terrace Deposits (Qt)
@ 20' to T.D. - Topanga Formation (Tt)
539
60 TEST TYPES: DSMD
SA
S&H
EI DIRECT SHEAR MAXIMUM DENSITY
SIEVE ANALYSIS
SIEVE AND HYDROMETER
EXPANSION INDEX
55 50
45 40
35 Elevation (ft) Depth (ft) Graphic Log Sample Number Blow Count Dry Density (pcf) Moisture (%) USCS Symbol DESCRIPTION Type of Test Date:
Project Name:
Project Number:
Elevation of Top of Hole:
Hole Location: See Geotechnical Map
Drilling Company:
Type of Rig:
Drop:
Drive Weight:
Hole Diameter:
30 CN CONSOLIDATION
CR CORROSION
AL ATTERBERG LIMITS CO COLLAPSE/SWELL RV R-VALUE
-#200 % PASSING # 200 SIEVE
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 CONDITIONS ENCOUNTERED. THE DESCRIPTIONS
PROVIDED ARE QUALITATIVE FIELD DESCRIPTIONS
AND ARE NOT BASED ON QUANTITATIVE
ENGINEERING ANALYSIS.
SAMPLE TYPES: B BULK SAMPLE R RING SAMPLE (CA Modified Sampler) G GRAB SAMPLE
SPT STANDARD PENETRATION
TEST SAMPLE GROUNDWATER TABLE
34 29
24 19
14 Geotechnical Boring Log Borehole HS-4
6/20/2023
69' MSL
6"
Truck Mounted Rig
30"
140 pounds
2R Drilling
Woodhart LLC- Laguna Beach
23106-01
Logged By JMN
Sampled By JMN
Checked By RLD
SPT-2 40
50/5"
Total Depth = 31'
Groundwater Not Encountered
Backfilled with Cuttings and Capped with AC Cold Patch
on 6/20/2023
@ 30' - Sandy SILT: light brownish gray, moist to slightly moist, hard
17.3 ML
540
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 CONDITIONS ENCOUNTERED. THE DESCRIPTIONS
PROVIDED ARE QUALITATIVE FIELD DESCRIPTIONS
AND ARE NOT BASED ON QUANTITATIVE
ENGINEERING ANALYSIS. CN CONSOLIDATION
CR CORROSION
AL ATTERBERG LIMITS CO COLLAPSE/SWELL RV R-VALUE
-#200 % PASSING # 200 SIEVE
DIRECT SHEAR MAXIMUM DENSITY
SIEVE ANALYSIS
SIEVE AND HYDROMETER
EXPANSION INDEX
TEST TYPES: DSMD
SA
S&H
EI
SAMPLE TYPES: B BULK SAMPLE R RING SAMPLE (CA Modified Sampler) G GRAB SAMPLE
SPT STANDARD PENETRATION
TEST SAMPLE GROUNDWATER TABLE
30 25
20 15
10 5
0 Elevation (ft) Depth (ft) Graphic Log Sample Number Blow Count Dry Density (pcf) Moisture (%) USCS Symbol DESCRIPTION Type of Test Hole Diameter:
Hole Location: See Geotechnical Map
Drop:
Type of Rig:
Project Number:
Elevation of Top of Hole: Drive Weight:
Drilling Company:
Project Name:
Date:
82 77
72 67
62 Geotechnical Boring Log Borehole HA-1
6/21/2023
87' MSL
3"
Truck Mounted Rig
N/A"
N/A pounds
LGC Geotechnical
Woodhart LLC- Laguna Beach
23106-01
Logged By JMN
Sampled By JMN
Checked By RLD
SM @ 0' - dry vegetation
@ 1' - Silty SAND: brown, dry, some gravel DS
R-1 B-1@ 2' - Silty,Clayey SAND: brown, dry, friable, some gravel
@ 5' - Silty SAND: light brown, slightly moist, 1-2" clasts, some asphalt
Total Depth = 5'
Groundwater Not Encountered
Backfilled with Cuttings on 6/20/2023
99.5 5.5 SC-SM
4.1 SM
541
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 CONDITIONS ENCOUNTERED. THE DESCRIPTIONS
PROVIDED ARE QUALITATIVE FIELD DESCRIPTIONS
AND ARE NOT BASED ON QUANTITATIVE
ENGINEERING ANALYSIS. CN CONSOLIDATION
CR CORROSION
AL ATTERBERG LIMITS CO COLLAPSE/SWELL RV R-VALUE
-#200 % PASSING # 200 SIEVE
DIRECT SHEAR MAXIMUM DENSITY
SIEVE ANALYSIS
SIEVE AND HYDROMETER
EXPANSION INDEX
TEST TYPES: DSMD
SA
S&H
EI
SAMPLE TYPES: B BULK SAMPLE R RING SAMPLE (CA Modified Sampler) G GRAB SAMPLE
SPT STANDARD PENETRATION
TEST SAMPLE GROUNDWATER TABLE
30 25
20 15
10 5
0 Elevation (ft) Depth (ft) Graphic Log Sample Number Blow Count Dry Density (pcf) Moisture (%) USCS Symbol DESCRIPTION Type of Test Hole Diameter:
Hole Location: See Geotechnical Map
Drop:
Type of Rig:
Project Number:
Elevation of Top of Hole: Drive Weight:
Drilling Company:
Project Name:
Date:
77 72
67 62
57 Geotechnical Boring Log Borehole HA-2
6/21/2023
82' MSL
3"
N/A
N/A"
N/A pounds
LGC Geotechnical
Woodhart LLC- Laguna Beach
23106-01
Logged By JMN
Sampled By JMN
Checked By RLD
10.0 SM @ 0' - Silty SAND: brown, dry, friable
GB-1 @ 1' - Silty SAND: brown, slightly moist, friable, roots GB-2
@ 3' - Clayey SAND: dark brown, moist, cohesive
13.3 CL
@ 4' - Clayey SAND: dark brown, moist, cohesive
GB-3
@ 5' - Sandy CLAY: brown, moist, pieces of roots
GB-4
@ 6' - Silty SAND: orangish brown, moist, friable GB-5
7.3 @ 7' - Silty SAND: brown, moist, friable
Total Depth = 7'
Groundwater Not Encountered
Backfilled with Cuttings on 6/21/2023 Last Edited: 6/26/2023 SM
SC
542
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 CONDITIONS ENCOUNTERED. THE DESCRIPTIONS
PROVIDED ARE QUALITATIVE FIELD DESCRIPTIONS
AND ARE NOT BASED ON QUANTITATIVE
ENGINEERING ANALYSIS. CN CONSOLIDATION
CR CORROSION
AL ATTERBERG LIMITS CO COLLAPSE/SWELL RV R-VALUE
-#200 % PASSING # 200 SIEVE
DIRECT SHEAR MAXIMUM DENSITY
SIEVE ANALYSIS
SIEVE AND HYDROMETER
EXPANSION INDEX
TEST TYPES: DSMD
SA
S&H
EI
SAMPLE TYPES: B BULK SAMPLE R RING SAMPLE (CA Modified Sampler) G GRAB SAMPLE
SPT STANDARD PENETRATION
TEST SAMPLE GROUNDWATER TABLE
30 25
20 15
10 5
0 Elevation (ft) Depth (ft) Graphic Log Sample Number Blow Count Dry Density (pcf) Moisture (%) USCS Symbol DESCRIPTION Type of Test Hole Diameter:
Hole Location: See Geotechnical Map
Drop:
Type of Rig:
Project Number:
Elevation of Top of Hole: Drive Weight:
Drilling Company:
Project Name:
Date:
79 74
69 64
59 Geotechnical Boring Log Borehole HA-3
6/21/2023
84' MSL
3"
N/A
N/A"
N/A pounds
LGC Geotechnical
Woodhart LLC- Laguna Beach
23106-01
Logged By JMN
Sampled By JMN
Checked By RLD
@ 0' - Silty SAND: brown, slightly moist, roots
@ 2' - Silty SAND: brown, thick roots, moist
@ 3' - Clayey SAND: brown, moist, roots
@ 4' - Clayey SAND: brown, very moist
@ 5' - Clayey SAND: brown, very moist
Total Depth = 5'
Groundwater Not Encountered
Backfilled with Cuttings on 6/21/2023 Last Edited: 6/26/2023 SM
SC
543
Appendix C
Laboratory Test Results
544
Project No. 23106-01 C-1 December, 2025
APPENDIX C
Laboratory Test Results
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 a table summarizing the test results.
Moisture and Density Determination Tests: Moisture content (ASTM D2216) and dry density determinations (ASTM D2937) were performed on driven samples obtained from the test borings. The results of these tests are presented in the boring logs. Where applicable, only moisture content was determined from undisturbed or disturbed samples.
Grain Size Distribution/Fines Content: 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 (ASTM D1140). Where applicable, 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 D6913 (sieve).
Sample Location Description % Passing #
200 Sieve
HS-3 @ 1-5 ft Clayey Sand 34
HS-4 @ 15 ft Silty Sand 45
Atterberg Limits: The liquid and plastic limits (“Atterberg Limits”) were determined per ASTM D4318 for engineering classification of fine-grained material and presented in the table below. The USCS soil classification indicated in the table below is based on the portion of sample passing the No. 40 sieve and may not necessarily be representative of the entire sample. The plots are provided in this Appendix.
Sample Location Liquid Limit
(%)
Plastic Limit
(%)
Plasticity
Index (%)
USCS
Soil
Classification
HS-1 @ 10 ft 30 14 16 CL
HS-3 @ 10 ft 36 18 18 CL
545
APPENDIX C (Cont’d)
Laboratory Test Results
Project No. 23106-01 C-2 December, 2025
Expansion Index: The expansion potential of selected representative samples was evaluated by the Expansion Index Test per ASTM D4829. The results are presented in the table below.
Sample
Location
Expansion
Index
Expansion
Potential*
HS-3 @ 1-5 ft 4 Very Low
* Per ASTM D4829
Direct Shear: Direct shear tests were performed on selected driven and remolded (90 percent relative compaction) samples, which were soaked for a minimum of 24 hours prior to testing.
The samples were tested under various normal loads using a motor-driven, strain-controlled, direct-shear testing apparatus (ASTM D3080). The plots are provided in this Appendix.
Consolidation: Consolidation tests were performed per ASTM D2435. Samples (2.4 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 provided in this Appendix.
Collapse/Swell Potential: A collapse test was performed per ASTM D4546. Samples (2.4 inches in diameter and 1 inch in height) were placed in a consolidometer and loaded to their approximate in-situ effective stress. The curve is presented in this Appendix.
Laboratory Compaction: The maximum dry density and optimum moisture content of typical materials were determined in accordance with ASTM D1557. The results are presented in the table below.
Sample Location Sample Description
Maximum
Dry Density
(pcf)
Optimum
Moisture
Content (%)
HS-3 @ 1-5 ft Dark Olive Gray Clayey Sand 128.5 8.5
546
APPENDIX C (Cont’d)
Laboratory Test Results
Project No. 23106-01 C-3 December, 2025
Soluble Sulfates: The soluble sulfate contents of selected samples were determined by standard geochemical methods (CTM 417). The test results are presented in the table below.
Sample Location Sulfate Content
(ppm)
Sulfate Content
( %)
HS-3 @ 1-5 ft 117 < 0.02
Chloride Content: Chloride content was tested per CTM 422. The results are presented below.
Sample Location Chloride Content
(ppm)
HS-3 @ 1-5 ft 41
Minimum Resistivity and pH Tests: Minimum resistivity and pH tests were performed in general accordance with CTM 643 and standard geochemical methods. The results are presented in the table below.
Sample Location pH Minimum Resistivity
(ohm-cm)
HS-3 @ 1-5 ft 7.5 1,950
547
HS-1 R-3 10' - 30 14 16 CL
HS-3 R-3 10' - 36 18 18 CL
Laguna Beach
Project Number:
Plasticity
Index (%) PI
23106-01
Date: Jul-23
Symbol Location.: Sample No.: USCS Plastic Limit
(%) PL
Liquid Limit
(%) LL
Passing No.
200 Sieve
(%)
Depth (ft)
ATTERBERG LIMITS
(ASTM D 4318)
0 10
20 30
40 50
60 70
0 20 40 60 80 100
Plasticity Index (P.I.)
Liquid Limit (L.L.)
PLASTICITY CHART - CLASSIFICATION OF FINE-GRAINED SOILS 548
Project Name: Laguna Beach Tested By: G. Bathala Date: 07/06/23 Project No.: 23106-01 Checked By: J. Ward Date: 07/12/23 Boring No.: Sample Type: Ring
Sample No.: Depth (ft.): 2.0
Soil Identification:
2.415 2.415 2.415
1.000 1.000 1.000
165.83 166.47 166.44
45.58 45.53 45.18
Before Shearing
186.34 186.34 186.34
182.28 182.28 182.28
58.78 58.78 58.78
0.0000 0.2588 0.2604
-0.0546 0.3714 0.4168
After Shearing
199.35 202.23 192.86
178.71 183.87 173.85
65.21 70.32 59.15
2.70 2.70 2.70
62.43 62.43 62.43
HA-1
Olive gray silty, clayey sand (SC-SM)
Sample Diameter(in):
Weight of Wet Sample+Cont.(gm):
Vertical Rdg.(in): Final
Vertical Rdg.(in): Initial
Sample Thickness(in.):
Weight of Sample + ring(gm):
R-1
DIRECT SHEAR TEST
Consolidated Drained - ASTM D 3080
Water Density(pcf):
Specific Gravity (Assumed):
Weight of Container(gm):
Weight of Dry Sample+Cont.(gm):
Weight of Ring(gm):
Weight of Container(gm):
Weight of Dry Sample+Cont.(gm):
Weight of Wet Sample+Cont.(gm):
DS HA-1, R-1 @ 2
549
Normal Stress (kip/ft²)
Peak Shear Stress (kip/ft²)
Shear Stress @ End of Test (ksf)
Deformation Rate (in./min.)
Initial Sample Height (in.)
Diameter (in.)
Initial Moisture Content (%)
Dry Density (pcf)
Saturation (%)
Soil Height Before Shearing (in.)
Final Moisture Content (%)
07-23
Project No.: 23106-01
Sample Type:
Ring
Olive gray silty, clayey sand
(SC-SM) 12.0
0.9454
18.2 Laguna Beach DIRECT SHEAR TEST RESULTS
Consolidated Drained - ASTM D 3080
12.2 0.8436
16.6 1.000
0.789
0.786
0.0025
1.000
2.415
1.000
2.415
2.000
1.371
1.368
0.0025
4.000
2.738
2.732
0.0025
12.1 0.8874
16.2 Soil Identification: 3.29
97.4 3.29
96.8 97.6
1.000
2.415
3.29 Boring No.
Sample No.
Depth (ft)
HA-1
R-1
2 0.00
1.00 2.00
3.00 4.00
0 0.1 0.2 0.3
Shear Stress (ksf)
Horizontal Deformation (in.)
0.00 1.00
2.00 3.00
4.00 0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00
Shear Stress (ksf)
Normal Stress (ksf)
DS HA-1, R-1 @ 2
550
Tested Sample:
HA-1 at 2 ft
33.2 Degrees 33.2 Degrees
0.11 ksf 0.10 ksf
Peak: At 0.30" Displacement:
DIRECT SHEAR PLOT
Project Number: 23106-01
Date: Jul-23
Laguna Beach
0 1
2 3
4 5
0 1 2 3 4 5
Shear Stress (ksf)
Normal Stress (ksf)
Peak At 0.30" Displacement
551
Project Name: Laguna Beach Tested By: G. Bathala Date: 06/29/23 Project No.: 23106-01 Checked By: J. Ward Date: 07/12/23 Boring No.: Sample Type: Ring
Sample No.: Depth (ft.): 7.5
Soil Identification:
2.415 2.415 2.415
1.000 1.000 1.000
203.33 207.42 206.36
42.48 45.69 43.05
Before Shearing
189.81 189.81 189.81
172.16 172.16 172.16
58.54 58.54 58.54
0.0000 0.2399 0.2372
-0.0118 0.2601 0.2641
After Shearing
217.59 226.54 233.00
191.97 200.85 208.69
55.47 65.21 70.32
2.70 2.70 2.70
62.43 62.43 62.43
HS-2
Olive lean clay (CL)
Sample Diameter(in):
Weight of Wet Sample+Cont.(gm):
Vertical Rdg.(in): Final
Vertical Rdg.(in): Initial
Sample Thickness(in.):
Weight of Sample + ring(gm):
R-2
DIRECT SHEAR TEST
Consolidated Drained - ASTM D 3080
Water Density(pcf):
Specific Gravity (Assumed):
Weight of Container(gm):
Weight of Dry Sample+Cont.(gm):
Weight of Ring(gm):
Weight of Container(gm):
Weight of Dry Sample+Cont.(gm):
Weight of Wet Sample+Cont.(gm):
DS HS-2, R-2 @ 7.5
552
Normal Stress (kip/ft²)
Peak Shear Stress (kip/ft²)
Shear Stress @ End of Test (ksf)
Deformation Rate (in./min.)
Initial Sample Height (in.)
Diameter (in.)
Initial Moisture Content (%)
Dry Density (pcf)
Saturation (%)
Soil Height Before Shearing (in.)
Final Moisture Content (%)
06-23
Project No.: 23106-01
Sample Type:
Ring
Olive lean clay (CL)
92.0 0.9882
18.8 Laguna Beach DIRECT SHEAR TEST RESULTS
Consolidated Drained - ASTM D 3080
96.7 0.9731
17.6 1.000
1.283
0.827
0.0017
1.000
2.415
1.000
2.415
2.000
1.877
1.358
0.0017
4.000
3.031
2.543
0.0017
93.6 0.9798
18.9 Soil Identification: 15.53
116.4
15.53 115.8 117.6
1.000
2.415
15.53 Boring No.
Sample No.
Depth (ft)
HS-2
R-2
7.5 0.00
1.00 2.00
3.00 4.00
0 0.1 0.2 0.3
Shear Stress (ksf)
Horizontal Deformation (in.)
0.00 1.00
2.00 3.00
4.00 0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00
Shear Stress (ksf)
Normal Stress (ksf)
DS HS-2, R-2 @ 7.5
553
Tested Sample:
HS-2 at 7.5 ft
30.2 Degrees 29.9 Degrees
0.71 ksf 0.23 ksf
Peak: At 0.30" Displacement:
DIRECT SHEAR PLOT
Project Number: 23106-01
Date: Jul-23
Laguna Beach
0 1
2 3
4 5
0 1 2 3 4 5
Shear Stress (ksf)
Normal Stress (ksf)
Peak At 0.30" Displacement
554
Project Name: Laguna Beach Tested By: G. Bathala Date: 07/05/23 Project No.: 23106-01 Checked By: J. Ward Date: 07/12/23 Boring No.: Sample Type: 90% Remold
Sample No.: Depth (ft.): 1-5
Soil Identification:
2.415 2.415 2.415
1.000 1.000 1.000
196.73 197.27 196.36
45.38 45.57 44.61
Before Shearing
164.40 164.40 164.40
155.85 155.85 155.85
52.57 52.57 52.57
0.0000 0.2628 0.2544
-0.0097 0.2792 0.2744
After Shearing
218.00 211.89 219.61
199.85 194.63 202.84
61.83 56.84 64.65
2.70 2.70 2.70
62.43 62.43 62.43
HS-3
Dark olive gray clayey sand (SC)
Sample Diameter(in):
Weight of Wet Sample+Cont.(gm):
Vertical Rdg.(in): Final
Vertical Rdg.(in): Initial
Sample Thickness(in.):
Weight of Sample + ring(gm):
B-1
DIRECT SHEAR TEST
Consolidated Drained - ASTM D 3080
Water Density(pcf):
Specific Gravity (Assumed):
Weight of Container(gm):
Weight of Dry Sample+Cont.(gm):
Weight of Ring(gm):
Weight of Container(gm):
Weight of Dry Sample+Cont.(gm):
Weight of Wet Sample+Cont.(gm):
DS HS-3, B-1 @ 1-5
555
Normal Stress (kip/ft²)
Peak Shear Stress (kip/ft²)
Shear Stress @ End of Test (ksf)
Deformation Rate (in./min.)
Initial Sample Height (in.)
Diameter (in.)
Initial Moisture Content (%)
Dry Density (pcf)
Saturation (%)
Soil Height Before Shearing (in.)
Final Moisture Content (%)
07-23
Project No.: 23106-01
Sample Type:
90% Remold
Dark olive gray clayey sand
(SC) 49.7
0.9903
13.2 Laguna Beach DIRECT SHEAR TEST RESULTS
Consolidated Drained - ASTM D 3080
50.1 0.9800
12.1 1.000
0.912
0.726
0.0025
1.000
2.415
1.000
2.415
2.000
1.569
1.342
0.0025
4.000
2.842
2.713
0.0025
50.0 0.9836
12.5 Soil Identification: 8.28
116.5
8.28 116.2 116.6
1.000
2.415
8.28 Boring No.
Sample No.
Depth (ft)
HS-3
B-1
1-5
0.00 1.00
2.00 3.00
4.00 0 0.1 0.2 0.3
Shear Stress (ksf)
Horizontal Deformation (in.)
0.00 1.00
2.00 3.00
4.00 0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00
Shear Stress (ksf)
Normal Stress (ksf)
DS HS-3, B-1 @ 1-5
556
Tested Sample:
HS-3 at 1-5 ft
32.7 Degrees 33.6 Degrees
0.28 ksf 0.04 ksf
Samples Remolded to 90% Relative Compaction
Peak: At 0.30" Displacement:
DIRECT SHEAR PLOT
Project Number: 23106-01
Date: Jul-23
Laguna Beach
0 1
2 3
4 5
0 1 2 3 4 5
Shear Stress (ksf)
Normal Stress (ksf)
Peak At 0.30" Displacement
557
Project Name: Tested By: GB/JD Date: 06/28/23
Project No.: Checked By: J. Ward Date: 07/12/23
Boring No.: Depth (ft.):
Sample No.: Sample Type:
Soil Identification:
Sample Diameter (in.): 2.415
Sample Thickness (in.): 1.000
Weight of Sample + ring (g): 209.18
Weight of Ring (g): 45.68
Height after consol. (in.): 0.9386
Before Test
Wt. of Wet Sample+Cont. (g): 191.94
Wt. of Dry Sample+Cont. (g): 174.73
Weight of Container (g): 56.13
Initial Moisture Content (%) 14.5
Initial Dry Density (pcf) 118.7
Initial Saturation (%): 87
Initial Vertical Reading (in.) 0.1105
After Test
Wt. of Wet Sample+Cont. (g): 273.18
Wt. of Dry Sample+Cont. (g): 254.24
Weight of Container (g): 65.58
Final Moisture Content (%) 13.25
Final Dry Density (pcf): 126.7
Final Saturation (%): 100
Final Vertical Reading (in.) 0.1750
Specific Gravity (assumed): 2.78
Water Density (pcf): 62.43
0.10 0.1118 0.9987 0.00 0.13 0.460 0.13
0.25 0.1221 0.9884 0.05 1.16 0.445 1.11
0.50 0.1289 0.9816 0.11 1.84 0.436 1.73
1.00 0.1380 0.9725 0.19 2.75 0.424 2.56
2.00 0.1482 0.9624 0.29 3.77 0.411 3.48
2.00 0.1483 0.9623 0.29 3.78 0.411 3.48
4.00 0.1552 0.9554 0.43 4.47 0.403 4.04
8.00 0.1701 0.9404 0.58 5.96 0.383 5.38
16.00 0.1902 0.9203 0.76 7.97 0.356 7.21
4.00 0.1859 0.9246 0.58 7.54 0.360 6.96
1.00 0.1788 0.9317 0.41 6.83 0.368 6.42
0.25 0.1750 0.9355 0.31 6.45 0.372 6.14
HS-1
R-3
Time
Corrected
Deformation (%)
PROPERTIES of SOILS
Ring
Void
Ratio
Dark olive brown sandy lean clay s(CL)
Time Readings
Elapsed
Time (min)
10.0 Pressure
(p)
(ksf) Dial Rdgs.
(in.) Date
ONE-DIMENSIONAL CONSOLIDATION
ASTM D 2435
23106-01
Laguna Beach
Deformation
% of Sample
Thickness Square
Root of
Time
Final
Reading
(in.)
Apparent
Thickness
(in.)
Load
Compliance
(%)
0.340
0.360
0.380
0.400
0.420
0.440
0.460
0.480
0.10 1.00 10.00 100.
Void Ratio
Pressure, p (ksf)
Inundate with
Tap water
Consol HS-1, R-3 @ 10
558
Initial Final Initial Final Initial Final Initial Final Soil Identification:
Time Readings
118.7 0.372 87 100
Degree of
Saturation (%) Dry Density (pcf)
0.462
Void Ratio
10 14.5
Dark olive brown sandy lean clay s(CL)
Project No.:
Laguna Beach
07-23
23106-01
Boring
No.
Sample
No.
Depth
(ft.)
Moisture
Content (%)
ONE-DIMENSIONAL CONSOLIDATION
PROPERTIES of SOILS
ASTM D 2435
HS-1 R-3 13.2 126.7
0.0000
0.2000
0.4000
0.6000
0.8000
1.0000
1.2000
0.1 1.0
Deformation Dial Reading (in.)
Log of Time (min.)
0.00 1.00
2.00 3.00
4.00 5.00
6.00 7.00
8.00 0.10 1.00 10.00 100.00
Deformation (%)
Pressure, p (ksf)
0.0000
0.2000
0.4000
0.6000
0.8000
1.0000
1.2000
0.0 10.0
Square Root of Time (min.1/2)
Inundate with
Tap water
559
Project Name: Tested By: GB/JD Date: 06/28/23
Project No.: Checked By: J. Ward Date: 07/12/23
Boring No.: Depth (ft.):
Sample No.: Sample Type:
Soil Identification:
Sample Diameter (in.): 2.415
Sample Thickness (in.): 1.000
Weight of Sample + ring (g): 198.67
Weight of Ring (g): 44.80
Height after consol. (in.): 0.9969
Before Test
Wt. of Wet Sample+Cont. (g): 207.01
Wt. of Dry Sample+Cont. (g): 193.18
Weight of Container (g): 56.97
Initial Moisture Content (%) 10.2
Initial Dry Density (pcf) 116.2
Initial Saturation (%): 61
Initial Vertical Reading (in.) 0.0166
After Test
Wt. of Wet Sample+Cont. (g): 264.13
Wt. of Dry Sample+Cont. (g): 241.86
Weight of Container (g): 57.93
Final Moisture Content (%) 16.01
Final Dry Density (pcf): 116.1
Final Saturation (%): 96
Final Vertical Reading (in.) 0.0225
Specific Gravity (assumed): 2.70
Water Density (pcf): 62.43
0.10 0.0170 0.9996 0.00 0.04 0.450 0.04
0.25 0.0202 0.9964 0.04 0.36 0.446 0.32
0.50 0.0223 0.9943 0.09 0.57 0.444 0.48
1.00 0.0247 0.9919 0.15 0.81 0.441 0.66
2.00 0.0275 0.9891 0.25 1.09 0.439 0.84
2.00 0.0230 0.9936 0.25 0.64 0.445 0.39
4.00 0.0273 0.9893 0.37 1.07 0.441 0.70
8.00 0.0353 0.9813 0.49 1.87 0.431 1.38
16.00 0.0470 0.9696 0.65 3.04 0.416 2.39
4.00 0.0416 0.9750 0.51 2.50 0.422 1.99
1.00 0.0295 0.9871 0.39 1.29 0.438 0.90
0.25 0.0225 0.9941 0.28 0.59 0.446 0.31
HS-3
R-3
Time
Corrected
Deformation (%)
PROPERTIES of SOILS
Ring
Void
Ratio
Olive lean clay with sand (CL)s
Time Readings
Elapsed
Time (min)
10.0 Pressure
(p)
(ksf) Dial Rdgs.
(in.) Date
ONE-DIMENSIONAL CONSOLIDATION
ASTM D 2435
23106-01
Laguna Beach
Deformation
% of Sample
Thickness Square
Root of
Time
Final
Reading
(in.)
Apparent
Thickness
(in.)
Load
Compliance
(%)
0.410
0.415
0.420
0.425
0.430
0.435
0.440
0.445
0.450
0.455
0.10 1.00 10.00 100.
Void Ratio
Pressure, p (ksf)
Inundate with
Tap water
Consol HS-3, R-3 @ 10
560
Initial Final Initial Final Initial Final Initial Final Soil Identification:
Time Readings
116.2 0.446 61 96
Degree of
Saturation (%) Dry Density (pcf)
0.451
Void Ratio
10 10.2
Olive lean clay with sand (CL)s
Project No.:
Laguna Beach
07-23
23106-01
Boring
No.
Sample
No.
Depth
(ft.)
Moisture
Content (%)
ONE-DIMENSIONAL CONSOLIDATION
PROPERTIES of SOILS
ASTM D 2435
HS-3 R-3 16.0 116.1
0.0000
0.2000
0.4000
0.6000
0.8000
1.0000
1.2000
0.1 1.0
Deformation Dial Reading (in.)
Log of Time (min.)
0.00 0.50
1.00 1.50
2.00 2.50
3.00 0.10 1.00 10.00 100.00
Deformation (%)
Pressure, p (ksf)
0.0000
0.2000
0.4000
0.6000
0.8000
1.0000
1.2000
0.0 10.0
Square Root of Time (min.1/2)
Inundate with
Tap water
561
Project Name: Tested By: G. Bathala Date: 07/07/23
Project No.: Checked By: J. Ward Date: 07/12/23
Boring No.: HS-4 Sample Type: Ring
Sample No.: R-4 Depth (ft.) 15.0
Sample Description: Olive gray silty clay (CL-ML)
Initial Dry Density (pcf): 110.5 Final Dry Density (pcf): 112.1 Initial Moisture (%): 11.40 Final Moisture (%) : 18.0
Initial Length (in.): 1.0000 Initial Void ratio: 0.5255 Initial Dial Reading: 0.0019 Specific Gravity(assumed): 2.70 Diameter(in): 2.415 Initial Saturation (%) 58.6
0.100 0.9999 0.00 -0.01 -0.01
2.000 0.9881 0.25 -1.19 -0.94
H2O 0.9879 0.25 -1.21 -0.96
Percent Swell (+) / Settlement (-) After Inundation = -0.02 Load
Compliance
(%)
Apparent
Thickness
(in)
ONE-DIMENSIONAL SWELL OR SETTLEMENT
POTENTIAL OF COHESIVE SOILS
ASTM D 4546
Corrected
Deformation
(%)
Laguna Beach
23106-01
0.5109
0.0020
0.0138
0.0140
Pressure (p)
(ksf)
0.5254
0.5112
Final Reading
(in) Void Ratio
Swell (+)
Settlement (-)
% of Sample
Thickness
0.5100
0.5120
0.5140
0.5160
0.5180
0.5200
0.5220
0.5240
0.5260
0.5280
0.100 1.000 10.000
Void Ratio
Log Pressure (ksf)
Void Ratio - Log Pressure Curve
Inundate with
Tap water
Swell or Settlement HS-4, R-4 @ 15
562
Appendix D
Infiltration Test Data
563
Boring Number:
Test hole dimensions (if circular)
5 8
3 Pre‐Test (Sandy Soil Criteria)*
1 8:00 8:25 25.0 1.87 1.88 0.01
2 8:25 8:50 25.0 1.88 1.89 0.01
Main Test Data
1 8:55 9:25 30.0 1.89 1.89 0.00 0.0
2 9:25 9:55 30.0 1.89 1.90 0.01 0.0
3 9:55 10:25 30.0 1.9 1.91 0.01 0.0
4 10:25 10:55 30.0 1.91 1.92 0.01 0.0
5 10:55 11:25 30.0 1.92 1.93 0.01 0.0
6 11:25 11:55 30.0 1.93 1.95 0.02 0.0
7 11:55 12:25 30.0 1.95 1.96 0.01 0.0
8 12:25 12:55 30.0 1.96 1.98 0.02 0.0
9 12:55 13:25 30.0 1.98 1.98 0.00 0.0
10 13:25 13:55 30.0 1.98 1.99 0.01 0.0
11 13:55 14:25 30.0 1.99 2.00 0.01 0.0
12 14:25 14:55 30.0 2.00 2.01 0.01 0.0
Feasibility Factor of Safety 2.0
0.0 Sketch:
Infiltration Test Data Sheet
LGC Geotechnical, Inc
131 Calle Iglesia Suite 200, San Clemente, CA 92672 tel. (949) 369‐6141 Project Name: Woodhart LLC- Laguna Beach
Project Number: 23106-01
Date: 6/22/2023
I-1
Test pit dimensions (if rectangular)
Boring Depth (feet)*: Pit Depth (feet):
Boring Diameter (inches): Pit Length (feet):
Pipe Diameter (inches): Pit Breadth (feet): *measured at time of test Trial No. Start Time
(24:HR)
Stop Time
(24:HR)
Time Interval
(min)
Initial Depth to
Water (feet)
Final Depth
to Water
(feet)
Total Change
in Water Level
(feet)
Greater Than or
Equal to
0.5 feet (yes/no)
No
No
*If two consecutive measurements show that six inches of water seeps away in less than 25 minutes, the test shall be run for an additional hour with measurements taken every 10 minutes. Otherwise, pre-soak (fill) overnight, and then obtain at least twelve measurements per hole over at least six hours (approximately 30 minute intervals) with a precision of at least 0.25 inches Trial No. Start Time
(24:HR)
Stop Time
(24:HR)
Time Interval,
Dt (min)
Initial Depth to
Water, Do (feet)
Measured Infiltration Rate (With Factor of Safety)
Based on Guidelines from: South Orange County 9/28/2017 Spreadsheet Revised on: 10/30/2019
Final Depth
to Water,
Df(feet)
Change in
Water Level,
DD (feet)
Measured
Infiltration
Rate(in/hr)
Measured Infiltration Rate (No Factor of Safety) 0.0
Notes: Standing water was observed in
infiltration boring 24 hrs after presoak
564
Boring Number:
Test hole dimensions (if circular)
5 8
3 Pre‐Test (Sandy Soil Criteria)*
1 8:12 8:37 25.0 3.14 3.23 0.09
2 8:38 9:03 25.0 2.97 3.07 0.10
Main Test Data
1 9:03 9:33 30.0 3.07 3.2 0.13 0.3
2 9:34 10:04 30.0 2.99 3.10 0.11 0.2
3 10:05 10:35 30.0 2.91 3.04 0.13 0.2
4 10:35 11:05 30.0 3.04 3.15 0.11 0.2
5 11:06 11:36 30.0 2.92 3.04 0.12 0.2
6 11:37 12:07 30.0 3.00 3.11 0.11 0.2
7 12:08 12:38 30.0 3.00 3.11 0.11 0.2
8 12:39 13:11 32.0 3.04 3.16 0.12 0.2
9 13:12 13:42 30.0 3.04 3.14 0.10 0.2
10 13:44 14:14 30.0 3.05 3.15 0.10 0.2
11 14:15 14:45 30.0 3.02 3.13 0.11 0.2
12 14:46 15:16 30.0 3.05 3.17 0.12 0.2
Feasibility Factor of Safety 2.0
0.1 Sketch:
Measured Infiltration Rate (With Factor of Safety)
Based on Guidelines from: South Orange County 9/28/2017 Spreadsheet Revised on: 10/30/2019
Notes: Standing water was observed in
infiltration boring 24 hrs after presoak
Final Depth
to Water,
Df(feet)
Change in
Water Level,
DD (feet)
Measured
Infiltration
Rate(in/hr)
Measured Infiltration Rate (No Factor of Safety) 0.2
Total Change
in Water Level
(feet)
Greater Than or
Equal to
0.5 feet (yes/no)
No
No
*If two consecutive measurements show that six inches of water seeps away in less than 25 minutes, the test shall be run for an additional hour with measurements taken every 10 minutes. Otherwise, pre-soak (fill) overnight, and then obtain at least twelve measurements per hole over at least six hours (approximately 30 minute intervals) with a precision of at least 0.25 inches Trial No. Start Time
(24:HR)
Stop Time
(24:HR)
Time Interval,
Dt (min)
Initial Depth to
Water, Do (feet)
Trial No. Start Time
(24:HR)
Stop Time
(24:HR)
Time Interval
(min)
Initial Depth to
Water (feet)
Final Depth
to Water
(feet)
*measured at time of test
Boring Depth (feet)*: Pit Depth (feet):
Boring Diameter (inches): Pit Length (feet):
Pipe Diameter (inches): Pit Breadth (feet):
Date: 6/22/2023
I-2
Test pit dimensions (if rectangular)
Infiltration Test Data Sheet
LGC Geotechnical, Inc
131 Calle Iglesia Suite 200, San Clemente, CA 92672 tel. (949) 369‐6141 Project Name: Woodhart LLC- Laguna Beach
Project Number: 23106-01
565
Appendix E
General Earthwork and Grading Specifications
566
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, moistureconditioning 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, the number of “equipment” of work and the estimated quantities of daily earthwork General Earthwork and Grading Specifications for Rough Grading Page 1 567
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). Nesting of the 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 over-excavated as specified in the following section. Scarification shall continue until soils are broken down and free of oversize material and the working surface is reasonably uniform, flat, and free of uneven features that would inhibit uniform compaction.
General Earthwork and Grading Specifications for Rough Grading Page 2 568
2.3 Over-excavation
In addition to removals and over-excavations 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 over-excavated 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 over-excavated 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 of 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 oversize 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.
General Earthwork and Grading Specifications for Rough Grading Page 3 569
3.3 Import
If importing of fill material is required for grading, proposed import material shall meet the requirements of the geotechnical consultant. 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.
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).
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). 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 sheepsfoot 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.
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).
General Earthwork and Grading Specifications for Rough Grading Page 4 570
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 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 General Earthwork and Grading Specifications for Rough Grading Page 5 571
General Earthwork and Grading Specifications for Rough Grading Page 6 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.
572
573
574
575
576
577
578
579
580
581