October 18, 2022
Updated December 30, 2025
Edwin & Amanda Kisiel Project No: 72653-00
247 Canyon Acres Drive Report No: 22-9143U
Laguna Beach, California 92651
Subject: Preliminary Geotechnical Investigation
Proposed New Single-Family Residence
2500 Glenneyre Street
Laguna Beach, California
INTRODUCTION
This report presents findings and conclusions of a preliminary geotechnical investigation undertaken to relate onsite and certain regional geotechnical conditions to the proposed construction of a single-family residence on the subject property. Analyses for this investigation are based upon conceptual designs by Mark Abel Architecture, and the Topographic Plan prepared by South Coast Surveying. The previous report was updated herein to reflect the current survey information.
This report is considered preliminary as no grading or foundation plans for the project are available, the preparation of which is dependent on the findings and recommendations presented in this report.
Scope of Investigation
The investigation included the following:
1. Review and analysis of pertinent reports, maps, aerial photographs, and published literature pertaining to the site and nearby areas, in order to relate geotechnical conditions to potential hazards at the property.
2. Field reconnaissance and the excavation, sampling, and geologic logging of four limitedaccess test pits to expose the shallow subsurface conditions and to determine the character and geometrical distribution of soil materials within the proposed construction areas. The maximum depth of exploration was approximately 3 feet below grade.
3. Laboratory testing of representative undisturbed and bulk samples to determine relevant soil characteristics, such as moisture, dry density, maximum density/optimum moisture, classification testing, expansion index, and/or corrosion properties.
4. Preparation of a site map and cross-sections relating the subsurface conditions to proposed construction and for use by engineers in the development of appropriate foundation design criteria.
Attachment 5
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5. Analyses of data and preparation of this geotechnical report presenting conclusions and recommendations for site development in accordance with the 2022 California Building Code and for use by your design professionals, contractors, and submittal to the City of Laguna Beach.
Accompanying Illustrations and Appendices
Figure 1 - USGS Geologic Location Map
Figure 2 - CGS Seismic Hazards Map
Figure 3 - Typical Retaining Wall Subdrain Detail
Figure 4 - Typical Subdrain for Caisson Retaining Wall
Figure 5 - Slab Subdrain Detail
Appendix A - References
Appendix B - Test Pit Logs
Appendix B-2 - Previous Test Pit Logs
Appendix C - Field Exploration and Laboratory Test Results Appendix D - Standard Grading Specifications
Appendix E - Utility Trench Backfill Specifications
Appendix F - Maintenance of Hillside Home Sites
Plate 1 - Geotechnical Plot Plan and Cross Sections A- - - Site Description The three roughly rectangular-shaped undeveloped lots front approximately 90 feet along Glenneyre Street and extend northeasterly approximately 90 feet to the rear property boundary within the undeveloped drainage area, as shown on Figure 1. Single-family residences occupy adjoining lots. Topographically, the proposed lot to be developed generally consists of a natural southwest-facing hillside slope with a seasonal stream running down the middle of the subject property, which descends at a ratio of approximately 2½:1 (horizontal:vertical). Maximum relief across the property is approximately 30 feet.
Proposed Development
Based on a review of the architectural plans prepared by Mark Abel Architecture, the proposed improvements include the construction of a three-level single-family residence on the southwestern portion of the subject property. The proposed structure will include a street-level terraced garage with retaining walls to a maximum height of 12+ feet supporting the upper twostory residence with a conventional and partially cantilevered design. We anticipate the design will utilize wood and steel-framing supported on retaining walls, possible piers, and perimeter foundations supporting a mix of slab on grade and raised wood flooring. 63 October 18, 2022 Project No: 72653-00
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GEOTECHNICAL CONDITIONS
Earth Materials
The property is underlain at shallow depth by bedrock assigned on the basis of regional mapping to the San Onofre Breccia, a rock formation of Miocene Age, consisting of breccia with interbedded conglomerate, sandstone, siltstone, mudstone, and minor diatomaceous shale and tuff. The breccia generally consists of gravel to cobble-sized angular clasts of metamorphic rock, suspended in a cemented sandy clay matrix. Bedrock is considered suitable for foundation support. The bedrock of the San Onofre Breccia is locally hard. Specialized equipment may be necessary for excavation.
Residual soil overlies the bedrock and is exposed at the ground surface in certain locations. The residual soil consists of brown, dry to moist, coarse-grained clayey sand to silty sand.
Geologic Structure
Based on regional mapping and nearby studies, the bedrock in the vicinity of the site is massive to crudely stratified and has a favorable history with regard to slope stability. Bedding planes exposed in the area of the site strike east-west to northeasterly and dip southerly between 24 and 45 degrees, as shown on Figure 2. Depending on the orientation of proposed excavations and other structures, the resulting structural-topographic relationship may be considered potentially adverse. Therefore, a Geofirm representative should observe all excavations.
Slope Stability
No evidence of gross slope instability has been reported, is depicted on regional maps, or has been observed during our onsite investigations of the site and immediate vicinity. The potential for deep-seated gross instability beneath the site is considered low due to the crudely bedded and cemented character of the underlying bedrock of the San Onofre Breccia.
Groundwater
Groundwater is not anticipated to be a construction nuisance or design constraint. However, perched groundwater may seasonally occur and may pose a construction nuisance during the rainy season.
Surficial Runoff
The proposed improvements will modify surface drainage, which should be controlled and outlet through appropriate landscape architectural or civil engineering design. 64 October 18, 2022 Project No: 72653-00
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Seismic Considerations
Published Studies
One of the principles of seismic analyses and prediction is the premise that earthquakes are more likely to occur on geologically younger faults and less likely to occur on older faults. For many years, studies have described faults with Holocene movement (within the last 11,700 years) as y, many studies
have described faults documented to ha
and seismic publications are attempting to clarify the nomenclature describing faults to more accurately represent the potential effects from earthquakes.
Reports by the California Division of Mines and Geology indicate faults with documented Holocene or Historic (within the last 200 years) movement should be considered Active.
However, Potentially Active faults are more appropriately characterized in terms of the last period of documented movement. The Fault Activity Map of California (Jennings, C.W.; 2015) defines four categories for onshore Potentially Active faults. The categories are associated with the time of the last displacement evidenced on a given fault and are summarized in Table 1.
Table 1. Definitions of Fault Activity in California
Activity Category Recency of Movement
Active Historic Within the last 200 years
Holocene Within the last 11,700 years
Potentially
Active
Late Quaternary Within the last 700,000 years
Quaternary Undifferentiated
Pre-Quaternary Before the last 1.6 million years
It is important to note that these categories embrace all Pre-Holocene faults as Potentially Active, an earthquake or movement occurring on a given fault significantly decreases with inactivity over geologic time, the potential for such events to occur on any fault cannot be eliminated within the current level of understanding.
Local and Regional Faults
The closest published active fault to the site is the offshore extension of the Newport-Inglewood Fault Zone, approximately 2 miles west (CGS/2004). Other active faults in the vicinity of the site include the San Joaquin Hills Fault, approximately 7 miles to the northeast, the Palos Verdes Fault, approximately 18 miles to the southwest; the Coronado Bank Fault, approximately 18 miles to the south; the Elsinore Fault, approximately 25 miles to the east, and the San Andreas Fault, approximately 53 miles to the northeast.
The offshore portion of the Newport-Inglewood Fault zone (NIFZ) is indicated in published reports as being a Potentially Active and Quaternary fault (Jennings, C.W., 2015). This 65 October 18, 2022 Project No: 72653-00
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interpretation is not universally shared, as this portion of the NIFZ is included as a potential seismic source in the computer programs utilized to model ground motions for this study. With 2 miles to the west, it is calculated as the most significant seismic source to affect this site. Given the present level of understanding of this offshore structure, it is, in our opinion, appropriate to include this portion of the fault as a causative seismic feature.
Ground Motion Analyses
Utilizing attenuation relationships (Bozorgnia et al., 1999, uncorrected/soft rock), one can estimate the ground motion history of the site. The study indicates the maximum site acceleration from 1800 to 2025 was approximately 0.1g, and occurred during the magnitude 6.3 Long Beach Earthquake, 13.4 miles from the site on March 11, 1933.
It is noted that the estimation of historic peak ground acceleration presented above is provided for the interest of the client and is required by local (City or County) review agencies. The value derived is not directly utilized in the structural design of residential structures. Seismic parameters for use by the structural engineer in accordance with the 2022 California Building Code in the design of the proposed structure(s) are presented in the recommendations portion of this report.
Site Classification for Seismic Design
For the purposes of determining seismic design parameters provided in the Recommendations portion of this report pertaining to the new structures, the upper one hundred feet of soil underlying the subject site has been classified in accordance with Section 1613 of the 2022 CBC.
Given the results of our onsite and nearby field investigations, which indicate the improvements will be found in bedrock, the site is classified as B.
Secondary Seismic Hazards
Review of the Seismic Hazards Zones Map (CDMG, 1998) for the San Juan Capistrano and Laguna Beach Quadrangles, Figure 3
for liquefaction or earthquake-induced landslides. This is consistent with the findings of this study.
Other secondary seismic hazards can include deep rupture, shallow ground cracking, and settlement. With the absence of active faulting onsite, the potential for deep fault rupture is not present. The potential for shallow ground cracking to occur during an earthquake is a possibility at any site, but it does not pose a significant hazard to site development. The elevation of the property is well above the anticipated Tsunami inundation. As the site is underlain at relatively shallow depth by bedrock, the magnitude of potential seismically induced settlement is considered negligible.
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CONCLUSIONS
1. The proposed construction at the subject site is considered geotechnically feasible, provided the recommendations herein are integrated into design, construction, and longterm maintenance. Proposed construction should not affect or be affected by adjacent properties, provided appropriate design and construction methods are utilized.
2. The property is underlain at relatively shallow depth by bedrock of the San Onofre Breccia. Competent bedrock is considered suitable for the support of new foundations supporting significant improvements.
3. No active faults are known to transect the site, and therefore, the site is not expected to be adversely affected by surface rupturing. It will, however, be affected by ground motions from earthquakes during the design life of the residence.
4. Based upon our current and previous laboratory test results, onsite earth materials have a low to medium expansion potential, a negligible soil soluble sulfate level, and a moderate potential for corrosion of buried metal.
5. Groundwater was not encountered during our subsurface investigation and is not considered a design or construction constraint.
6. Surface water drainage should be evaluated and improved as necessary by a landscape architect or civil engineer.
7. The proposed residence should be supported on conventional foundations supported in competent bedrock deposits. The cantilevered sections of the proposed residence should be supported on caissons constructed at least 10 feet into competent bedrock deposits and deepened where necessary to an adequate slope setback.
RECOMMENDATIONS
Site Preparation and Grading
1. General
All grading should be performed in accordance with the Standard Grading Specifications in Appendix D. Grading will likely include minor cut and fill operations to construct the building pad, exterior grades, and backfill of any retaining walls.
2. Remedial Grading
Remedial grading is recommended to include the re-compaction of existing residual soils.
Over-excavation is anticipated to consist of the removal of the upper 2 to 3± feet of 67 October 18, 2022 Project No: 72653-00
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existing residual soil material down to competent bedrock deposits prior to placement of additional fill soil to achieve site grades.
Local deeper removals may be required as determined by the geologist during construction. Processing, over-excavation, and re-compaction should be observed, tested, and approved in writing by a representative of this firm. Locally deeper removals may be recommended by the geologist during grading. Processing, over-excavation, and recompaction should be observed, tested, and approved in writing by a representative of this firm.
3. Removal of Existing Improvements
Any existing vegetation, trash, and/or construction and irrigation debris should be removed and disposed of off-site.
4. Compaction Standard
On-site soil materials are anticipated to be suitable for re-use as compacted fill. Such materials should be placed at 120 percent of optimum moisture content and compacted under the supervision of the soil engineer to at least 90 percent of the maximum dry density as determined by ASTM D 1557.
5. Construction Slopes
The grading of temporary construction slopes can create two potentially adverse conditions affecting the property and onsite personnel. These conditions include slope instability and safety. As the geotechnical consultant, we are limited to recommending temporary slope geometries considered stable, such that slope failures, should they occur, are not anticipated to adversely impact adjoining properties or structures. While our recommendations may often comply with safety guidelines concerning temporary slopes, Cal/OSHA. The safety of onsite personnel is the responsibility of the general contractor as described below. Temporary excavations should not be surcharged.
A. Protection of Property
In order to reduce the potential risk to nearby improvements, temporary construction slopes exposing onsite earth materials may be excavated vertically to a maximum height of 10 feet, with higher slopes laid back no steeper than 1:1 (horizontal:
vertical), pending field review by the geologist during grading. Shoring should be anticipated where space or grading limitations preclude temporary slope layback or in locations where workers may be in close proximity to vertical cuts. 68 October 18, 2022 Project No: 72653-00
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B. Worker Safety
As the safety of onsite personnel affected by the performance of temporary construction slopes is the responsibility of the general contractor, the contractor is recommended to implement the safety practices as defined in Section 1541, Subchapter 4, of Cal/OSHA T8 Regulations (2006).
The geometry of permissible temporary cuts varies based on soil type and may differ significantly from the geometry presented in Section A. The earth materials exposed in temporary excavations should be evaluated and classified by the contractor during construction.
Structural Design of Foundations and Slabs
Earth materials to be exposed at finish grades exhibit a low to medium expansion potential. We recommend that the foundation and slabs be designed to resist the effects of expansive soils in accordance with Section 1808.6.1 of the 2022 California Building Code. Foundations and slabs should be designed for the intended use and loading by the Structural Engineer. The design should consider the expansion potential of the subgrade soils and other appropriate soil-related criteria. The foundation and slab design should consider an effective plasticity index of 25.
Although there is no known economical method of totally preventing movement due to expansive soils, current state-of-the-practice in the southern California area dictates substantial reinforcement, slab thickening, moisture barriers, and pre-soaking of sub-grade soils as methods of reducing the effects of expansive soils. Reasonable mitigation of expansive soil effects is considered feasible from a geotechnical viewpoint, utilizing such methods, although it is noted that some future distress cannot be precluded when building on expansive soils.
Our recommendations are considered to be generally consistent with the standards of practice.
They are based on both analytical methods and empirical methods derived from experience with similar geotechnical conditions. These recommendations are considered the minimum necessary for the likely soil conditions and are not intended to supersede the design of the Structural Engineer or the criteria of governing agencies.
1. Conventional Foundations and Slabs-on-Grade
Conventional spread and continuous footings should be designed in accordance with the 2022 California Building Code. Footings may be designed for an allowable bearing value of 4,000 pounds per square foot for competent bedrock deposits, with a minimum width of 18 inches and a minimum embedment of 24 inches below the lowest adjacent grade and extending at least 12 inches into competent bedrock. Deepened excavations may be necessary in isolated areas to meet embedment recommendations. A geologist from our office should review the foundation excavations to verify proper embedment into competent bedrock. The design value may be increased by one-third for short-duration 69 October 18, 2022 Project No: 72653-00
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wind or seismic loading. Estimated settlements from structural loading are less than ½ inch total and ¼ inch differential.
Lateral loads may be resisted by passive pressure forces and by friction acting on the bottom of footings. The allowable passive pressure forces for bedrock may be computed using an equivalent fluid density of 400 pounds per cubic foot up to a maximum of 4,000 pounds per square foot. A coefficient of friction of 0.35 may be used in computing the frictional resistance in bedrock. Friction resistance and passive pressure may be combined without reduction.
A minimum slab thickness of 5 inches (actual) is recommended with minimum slab reinforcement of No. 4 bars spaced at 16 inches each way in the middle-third of the slab.
Slabs should be underlain by 4 inches of ½ to ¾ inch open graded gravel. Slab underlayment is deferred to the project architect; however, in accordance with the American Concrete Institute, we suggest that slabs be underlain by a 15-mil-thick vapor retarder/barrier (Stego Wrap or equivalent) placed over the gravel in accordance with the requirements of ASTM E:1745 and E:1643.
2. Moisture Content of Slab Subgrade Soils
Presoaking of slab subgrade soils is recommended prior to the construction of new slab areas. Moisture conditioning should be to 120 percent of optimum moisture content to a depth of at least 12 inches below the subgrade. The subgrade should be geotechnically approved prior to placing gravel.
3. Slab Subdrains or Waterproofing
Percolating irrigation and meteoric water may perch on top of less pervious layers at shallow depth beneath the site. Groundwater effects on basement-like elements can be reduced by intercepting seepage groundwater with a subdrain constructed beneath slabs (refer to Figure 5). As an alternative to the suggested slab subdrain system, lower slabs may be waterproofed. Slab waterproofing design and details should be provided by the project architect or waterproofing consultant.
Structural Design of Caissons
Caissons utilized for foundations should be twenty-four-inch diameter and embedded a minimum of 10 feet below into competent bedrock materials. Caissons may be designed for a dead plus live load end bearing value of 5,000 pounds per square foot and a skin friction of 500 pounds per square foot for portions embedded in bedrock. These values may be increased by one-third for wind and seismic forces. Settlement from loading is anticipated to be approximately 1/2-inch total and 1/4-inch differential over a horizontal distance of 20 feet.
Lateral resistance may be computed below the creep zone utilizing 400 pounds per square foot per foot of depth for bedrock acting on a tributary area of twice the caisson diameter. A 70 October 18, 2022 Project No: 72653-00
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minimum 24-inch diameter caisson is required in order to verify proper cleanout by the contractor and to allow visual observation and confirmation by the engineering geologist.
Although not currently proposed, caissons supporting near or on-slope improvements should be designed to resist an additional creep load equal to an equivalent fluid pressure of 60 pounds per cubic foot for a depth of 5 feet below the existing or finished slope grade, whichever is deeper.
Structural Design Pertaining to Soil/Slope Creep
It is generally accepted that soil creep is a surficial slope instability condition that is progressive in character and caused in this climatic environment by weathering expansion and contraction of sloping earth materials under the influence of moisture changes and gravity. The potential for structural distress of shallow foundation systems placed in or adjacent to creeping materials is high, as the creep process removes downslope support for conventional footings. Soil creep will affect those portions of the lot on or adjacent to the slopes.
Potential distress associated with creep-induced foundation deformations should be anticipated and reduced with an appropriate design that considers that most of the downslope movement of creep-prone materials at this site will occur in the upper 5± feet of sloping earth material, measured vertically from existing slope grades. The depth of creep should be field evaluated as conditions are exposed during excavation.
Additionally, deformations caused by movement cannot be entirely precluded, and it is the intent of these recommendations only to minimize their perception. Other design considerations that will minimize the perception of movement include the use of flexible surfacing materials rather than frangible materials such as tile, brick, and stucco.
Structural Design of Retaining Walls
1. Lateral Loads
Active pressure forces acting on unsurcharged retaining walls that are backfilled with level, free-draining granular material may be computed based on an equivalent fluid pressure of 35 pounds per cubic foot. Possible topographic or structural surcharges should be addressed by the structural engineer. Restrained walls should be designed for 60 pounds per cubic foot equivalent fluid pressure. Limited wall deformations normally occur and should be considered in the design of finished surfaces.
A dynamic lateral force should be applied to retaining walls 6 feet or more in height. The site is classified as being in Seismic Design Category D (Type II occupancy, SDs > 0.5g, SD1 > 0.2g). Seismic design of retaining walls may be based on the Mononobe-Okabe method, as updated by Atik and Sitar (2010), using an additional dynamic load of 16 pounds per cubic foot equivalent fluid pressure, acting at 1/3 H above the base of the wall. Final design requirements should be provided by the structural engineer. 71 October 18, 2022 Project No: 72653-00
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2. Subdrains
The drainage scheme depicted on Figure 3, or geotechnically approved alternatives, should be used to mitigate seepage forces behind retaining walls. The details of subdrain systems are referred to the wall designer, builder, or waterproofing consultant. The subdrain is not a substitute for waterproofing.
3. Retaining Wall Foundations
Bearing capacity and lateral resistance may be computed using the parameters presented in the foundation sections above.
Seismic Structural Design
Based on the geotechnical data and site parameters, the following is provided by the USGS to satisfy the 2022 CBC design criteria:
Site and Seismic Design Criteria for 2022 CBC
Concrete
Laboratory test results indicate onsite-derived soils have a negligible soluble sulfate content. It is recommended that a concrete expert be retained to design an appropriate concrete mix to address the structural requirements. In lieu of retaining a concrete expert, it is recommended that the 2022 California Building Code, Section 1904.1 be utilized, which refers to ACI 318, Table 4.3.1.
Design
Parameters
Recommended
Values
Site Class
Site Longitude (degrees)
Site Latitude (degrees)
Ss (g)
S1 (g)
SMS (g)
SM1 (g)
SDS (g)
SD1 (g)
Fa Fv Seismic Design Category
PGAM (g)
B (Estimated)
-117.764682
33.524570
1.330
0.472
1.33 0.472
0.887
0.315
1.0 1.0
D
0.584
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Slope Setbacks
The proposed improvements appear to be adequately setback from slopes. In accordance with the 2022 CBC, the bottom of foundations should be set back from the slope face a minimum distance of H/3, where H is the height of the slope measured from the toe of the onsite slope along the rear property line and the lowest structural foundation elements (adjacent to the planned pool). The minimum foundation setback distance is 10 feet from the descending slope face.
Hardscape Design and Construction
Hardscape improvements may utilize conventional foundations embedded in new engineered fill prepared in accordance with the remedial grading recommendations, or alternatively may be founded into competent bedrock materials and should be designed in accordance with the foundation recommendations presented below.
Conventional spread footings may be designed for an allowable bearing value of 1,500 or 4,000 pounds per square foot, for new engineered fill or competent bedrock materials, respectively.
Footings may be designed with a minimum width of 15 inches and a minimum embedment of 18 inches below the lowest adjacent grade. Deepened excavations may be necessary in isolated areas to meet embedment recommendations. A geologist from our office should review the foundation excavations to verify proper embedment into competent bedrock. Actual footing depth and width should be governed by CBC requirements and engineering design. The design value may be increased by one-third for short-duration wind or seismic loading.
Lateral loads may be resisted by passive pressure forces and by friction acting on the bottom of footings. The allowable passive pressure forces may be computed using an equivalent fluid density of 150 or 400 pounds per cubic foot for new engineered fill or competent bedrock deposits, respectively. A coefficient of friction of 0.25 may also be used in computing the frictional resistance.
Concrete flatwork should be divided into as nearly square panels as possible. Joints should be provided at maximum 6-foot intervals to give articulation to the concrete panels. Landscaping and planters adjacent to concrete flatwork should be designed in such a manner as to direct drainage away from concrete areas to approved outlets. Planters located adjacent to principal foundation elements should be sealed and drained.
Flatwork elements should be a minimum of 5 inches thick (actual) and reinforced with No. 4 bars 16 inches on center both ways.
Monitoring
Complete documentation of the pre- and post-construction conditions of adjacent improvements should be undertaken. In addition, monitoring of ground movement and construction vibrations should be made as an integral part of the construction. Such documentation should include:
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1. A sufficient number of photographs to establish the existing condition of nearby structures.
2. Establishment of a sufficient number of ground elevation control stations so that potential subsidence or heave associated with grading and lateral movement can be detected.
Monitoring of such points should be accomplished during all grading, shoring (if any), and excavation work, and continued until retaining walls are backfilled or site grading is complete.
Finished Grade and Surface Drainage
Finished grades should be designed and constructed so that no water ponds in the vicinity of footings or drains over the rear slope. Drainage design in accordance with the California Building Code, Section 1804.4 is recommended. Proper interception and disposal of onsite surface discharge is presumed to be a matter of civil engineering or landscape architectural design.
Foundation Plan Review
In order to help assure conformance with recommendations of this report and as a condition of the use of this report, the undersigned should review final foundation plans and specifications prior to submission of such to the building official for issuance of permits. Such a review is to be performed only for the limited purpose of checking for conformance with the design concept and the information provided herein. This review shall not include a review of the accuracy or completeness of details, such as quantities, dimensions, weights, or gauges, fabrication processes, construction means or methods, coordination of the work with other trades or construction safety precautions, all of which are the sole responsibility of the Contractor. e promptness while allowing sufficient time
in our judgment to permit adequate review. Review of a specific item shall not indicate that Geofirm has reviewed the entire system of which the item is a component. Geofirm shall not be responsible for any deviation from the Construction Documents not brought to our attention in writing by the Contractor. Geofirm shall not be required to review partial submissions or those for which submissions of correlated items have not been received.
Pre-Construction Meeting
A pre-construction meeting should be held with representatives of the owner, contractor, architect, civil engineer, geotechnical engineer, engineering geologist, and building official prior to grading and/or construction to clarify any questions relating to the incorporation of geotechnical recommendations into grading, construction, and work sequence.
Jobsite Safety
subconsultants at a construction/project site, shall relieve the General Contractor of its 74 October 18, 2022 Project No: 72653-00
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obligations, duties and responsibilities including, but not limited to, construction means, methods, sequence, techniques or procedures necessary for performing, superintending and coordination of the work in accordance with the contract documents and any health or safety precautions required by any regulatory agencies. Geofirm and its personnel have no authority to exercise any control over any construction contractor or its employees in connection with their work or any health or safety programs or procedures. The General Contractor shall be solely responsible for jobsite safety.
Observation and Testing
The 2022 California Building Code, Section 1705.6 requires geotechnical observation and testing during construction to verify proper removal of unsuitable materials, that foundation excavations are clean and founded in competent material, to test for proper moisture content and proper degree of compaction of fill, to test and observe placement of wall and trench backfill materials, and to confirm design assumptions. It is noted that the CBC requires continuous verification and testing during placement of fill, pile driving, and pier/caisson drilling.
A Geofirm representative shall visit the site at intervals appropriate to the stage of construction, as notified by the Contractor, in order to observe the progress and quality of the work completed by the Contractor. Such visits and observation are not intended to be an exhaustive check or a , but rather are to allow Geofirm, as an experienced
professional, to become generally familiar with the work in progress and to determine, in general, if the work is proceeding in accordance with the recommendations of this report. , nor have any
responsibility for the construction means, methods, techniques, sequences, or procedures selected by the Contractor,
work. These rights and responsibilities are solely those of the Contractor. Geofirm shall not be responsible for any acts or omissions of the Contractor, subcontractor, any entity performing any portion of the work, or any agents or employees of any of them. Geofirm does not guarantee the its work in accordance with the Contractor documents or any applicable law, codes, rules, or regulations.
These observations are beyond the scope of this investigation and budget and are conducted on a time and material basis. The responsibility for timely notification of the start of construction and ongoing geotechnically involved phases of construction is that of the owner and his contractor.
Typically, at least a 24-hour notice is required.
LIMITATIONS
This investigation has been conducted in accordance with generally accepted practice in the engineering geologic and soils engineering field. No further warranty is offered or implied.
Conclusions and recommendations presented are based on subsurface conditions encountered and are not meant to imply a control of nature. As site geotechnical conditions may alter with 75 October 18, 2022 Project No: 72653-00
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time, the recommendations presented herein are considered valid for a time period of one year from the report date. The recommendations are also specific to the current proposed development. Changes in proposed land use or development may require supplemental investigation or recommendations. Also, independent use of this report in any form cannot be approved unless specific written verification of the applicability of the recommendations is obtained from this firm.
Thank you for this opportunity to be of service. If you have any questions, please contact this office.
Respectfully submitted,
GEOFIRM
Kevin A. Trigg, P.G. Jesse Bearfield, P.E. 84335
Chief Engineering Geologist, E.G. 1619 Associate Engineer KAT/JDB : mr
Distribution: Email to Addressee
76 77
78 JOB NO.: DATE: FIGURE:
Typical Retaining Wall Subdrain Detail
72653-00 December 2025 3
Onsite Native Soil Cap for
exterior ; (1.5'-2.0' MAX. thick)
Select Noncohesive
Granular Backfill
(SE > 30)
Retaining Wall Footing
Geotextile Filter Fabric
4" Perforated Plastic Collector Pipe
(Below Adjacent Finish Grade)
Single-sized 1/2"- 3/4" Drain Rock
(1 cubic foot per lineal foot)
Limit of Wall Excavation -
See Report for
Recommended Geometery
Typical
Retaining
Wall
Notes: This system consists of a geotextile fabric-wrapped gravel envelope. Collection is with a 4-inch diameter perforated plastic pipe embedded in the gravel envelope and tied to a 4-inch diameter non-perforated plastic pipe which discharges at convenient locations. The outlet pipe should be placed such that the flow gradient is not less than 2.0 percent. The geotextile fabricwrapped gravel envelope should be placed at a similar gradient All drain pipes should be Schedule 40 PVC or ABS SDR-35. Perforations may be either bored 1/4-inch diameter holes or 3/16-inch slots placed on the bottom one-third of the pipe perimeter. If the pipe is to be bored, a minimum of 10 holes should be uniformly placed per foot of length. If slots are made, they should not exceed 2-1/2 inches in length and should not be closer than 2 inches. Total length of slots should not be less than 50 percent of the pipe length and should be uniformly spaced.
The fabric pore spaces should not exceed equivalent 30 mesh openings or be less than equivalent 100 mesh openings. The fabric should be placed such that a minimum lap of 8-inches exists at all splices.
18" min
Finish Grade - Design May
Vary per Architect or Civil
Engineer
Alternative Weep Hole(s)
for Exterior Applications,
Design per Architect or
Civil Engineer
79 JOB NO.: DATE: FIGURE:
Typical Subdrain for Caisson Retaining Wall
72653-00 ber 202 4
Caisson
Waterproofing per
Architectural Plan
Finished Reinforced
Retaining Wall and/or
Shotcrete Wall between
Caissons
Native Soil
Shoring Lagging
Mirafi Quickdrain, or
approved equivalent,
outletted to sump pump
Miradrain or
approved
equivalent
Retained Earth
Material
Embedded Reinforcement
per Structural
80 JOB NO.: DATE: FIGURE:
Slab Subdrain Detail
7 -00 5
Concrete Slab
4" Gravel Layer
Single Sized 1/2 to 3/4-inch
Drain Rock
15-mil visqueen membrane
overlaying gravel
Native Soil
Geotextile Filter
Fabric
Perforated 4" PVC
Schedule 40 Drain
Pipe
12" min
12" min
81 APPENDIX A
REFERENCES
82 APPENDIX A
REFERENCES
1. Al Atik, Linda, M. ASCE, and Sitar, Nicholas, M.ASCE, 2010, Seismic Earth Pressures on Cantilever Retaining Structures, ASCE Journal of Geotechnical and Geoenvironmental Engineering, dated October.
2. Characteristics, Relationship with Horizontal Component, and Building Code -Motion Data,
pp. 23-49, dated September 15.
3. California Building Code, 2022 Edition.
4. . 5.
. 6.
Point Quadrangle.
7. California Geological Survey
http://gmw. consrv.ca.gov/shmp/index.htm.
8. Cao, T., Bryant, W.A., Rowshandel, B., Branum, D.,
2002 California Probabilistic Seismic Hazard Maps, dated June.
9. -00, Report
No. 18-8271, dated April 2.
10. California Division of Mines and Geology, Geologic Data Map No. 6.
11. SEAOC and OSHPD
12. United States Geological Survey, 2002, "Preliminary Digital Geologic Map of the Long Beach 30' x 60' Quadrangle, southern California, Version 1.0". 83 APPENDIX B
TEST PIT LOGS
84 85
86 87
88 APPENDIX B-2
PREVIOUS TEST PIT LOGS
89 90
91 92
APPENDIX C
FIELD EXPLORATION AND LABORATORY TEST RESULTS
93 APPENDIX C
FIELD EXPLORATION AND LABORATORY TEST RESULTS
I. Field Exploration Procedures
A. Field Exploration
Subsurface soils were exposed utilizing hand-held tools and electrical equipment.
Disaggregated, or bulk, soil samples were obtained at the surface from the spoil pile as the excavation advanced. These soils were bagged and transported to our laboratory for testing. Core samples of subsurface materials were obtained by driving a steel barrel drive sampler. Samplers were driven utilizing a 20-pound weight that was raised and permitted to fall 12 inches. The sampler has an outside diameter of 3.0 inches and is lined with a series of 1-inch high brass rings having an inside diameter of 2.43 inches. A drive shoe is placed on the tip of the sampler to hold the liners in place during sampling.
The samples were removed from the sample barrel in the brass rings, placed in moisture-tight containers, and transported to the laboratory for testing.
II. Laboratory Testing Procedures
A. Moisture Content and Dry Density Test
The moisture content and dry density determination were made in accordance with ASTM test methods. The results are summarized in Figure C-1.
B. Corrosion Test Results
A series of corrosivity tests was performed on a specimen of soil. The testing includes an evaluation of sulfate content in accordance with California test method 417, a pH evaluation in accordance with ASTM D 4972, and a minimum resistivity evaluation in accordance with California test method 643.
The test results are presented below.
Sample Designation - HA-4 @ 0-
pH - 7.1
Soluble Sulfate - 49 mg/kg
Minimum Resistivity - 2,160 ohm-cm
Soluble Chloride - 21 mg/kg
94 C. Gradation Test
Grain size was evaluated for a representative soil sample in accordance with ASTM D 422. The results are shown on Figure C-2.
D. Maximum Density and Optimum Moisture Content
Optimum moisture and maximum density were evaluated in accordance with Test Designation ASTM D 1557. These results are tabulated below and depicted on the attached Figure C-3.
Sample
Location
Optimum Moisture Content
(%)
Maximum Dry Density
(pcf)
HA-1 13.3 118.1
E. Expansion Index Test
An expansion index test was performed in accordance with UBC Standard No. 29-2. The results of the test are tabulated below:
Sample Designation - HA-3 @ 0- HA-4 @ 0-
Expansion Index - 50 55
Expansion Classification - Low Medium
95 96
97 98
APPENDIX D
STANDARD GRADING SPECIFICATIONS
99 APPENDIX D
STANDARD GRADING SPECIFICATIONS
GENERAL
These specifications present the usual and minimum requirements for grading operations observed by Geofirm or its designated representative. No deviation from these specifications will be allowed, except where specifically superseded in the geotechnical report signed by a registered geotechnical engineer.
The placement, spreading, mixing, watering, and compaction of the fills in strict accordance with these guidelines shall be the sole responsibility of the contractor. The construction, excavation, and placement of fill shall be under the direct observation of the soils engineer signing the soils report. If unsatisfactory soil-related conditions exist, the soils engineer shall have the authority to reject the compacted fill ground, and if necessary, excavation equipment will be shut down to permit completion of compaction. Conformance with these specifications will be discussed in the final report issued by the soils engineer.
SITE PREPARATION
Brush, vegetation, and other deleterious material such as rubbish shall be collected, piled, and removed from the site prior to placing fill, leaving the site clear and free from objectionable material.
Soil, alluvium, or rock materials determined by the soils engineer as being unsuitable for placement in compacted fills shall be removed from the site. Any material incorporated as part of a compacted fill must be approved by the soils engineer.
The surface shall then be plowed or scarified to a minimum depth of 6 inches until the surface is free from uneven features that would tend to prevent uniform compaction by the equipment used.
After the area to receive fill has been cleared and scarified, it shall be diced or bladed by the contractor until it is uniform and free from large clods, brought to the proper moisture content, and compacted to the minimum requirements. If the scarified zone is greater than 12 inches in depth, the excess shall be removed and placed in lifts restricted to 6 inches.
Underground structures such as cesspools, cisterns, mining shafts, tunnels, septic tanks, wells, pipe lines, or others not located prior to grading are to be removed or treated in a manner prescribed by the soils engineer.
MATERIALS
Materials for compacted fill shall consist of materials approved by the soils engineer. These materials may be excavated from the cut area or imported from other approved sources, and soils 100
from one or more sources may be blended. Fill soils shall be free from organic vegetable matter and other unsuitable substances. Normally, the material shall contain no rocks or hard lumps greater than 6 inches in size and shall contain at least 50 percent of material smaller than 1/4- inch in size. Materials greater than 4 inches in size shall be placed so that they are completely surrounded by compacted fines; no nesting of rocks shall be permitted. No material of a perishable, spongy, or otherwise unsuitable nature shall be used in the fill soils.
Representative samples of materials to be utilized as compacted fill shall be analyzed in the laboratory by the soils engineer to determine their physical properties. If any material other than that previously tested is encountered during grading, the appropriate analysis of this material shall be conducted by the geotechnical engineer as soon as possible.
PLACING, SPREADING, AND COMPACTING FILL MATERIAL
The material used in the compacting process shall be evenly spread, watered, processed, and compacted in thin lifts not to exceed 6 inches in thickness to obtain a uniformly dense layer.
When the moisture content of the fill material is below that specified by the soils engineer, water shall be added by the contractor until the moisture content is near optimum as specified.
When the moisture content of the fill material is above that specified by the geotechnical engineer, the fill material shall be aerated by the contractor by blading, mixing, or other satisfactory methods until the moisture content is near optimum as specified.
After each layer has been placed, mixed, and spread evenly, it shall be thoroughly compacted to 90 percent of the maximum laboratory density in compliance with ASTM D: 1557-70 (five layers). Compaction shall be accomplished by sheepsfoot rollers, vibratory rollers, multiplewheel pneumatic-tired rollers, or other types of acceptable compacting equipment. Equipment shall be of such design that it will be able to compact the fill to the specified density.
Compaction shall be continuous over the entire area, and the equipment shall make sufficient passes to obtain the desired density uniformly.
A minimum relative compaction of 90 percent out to the finished slope face of all fill slopes will be required. Compacting of the slopes shall be accomplished by backrolling the slopes in increments of 2 to 5 feet in elevation gain or by overbuilding and cutting back to the compacted inner core, or by any other procedure which produces the required compaction.
OBSERVATIONS AND TESTING
The geotechnical engineer shall observe the placement of fill during the grading process and will file a written report upon completion of grading stating his observations as to compliance with these specifications.
101
One density test shall be required for each 2 vertical feet of fill placed, or one for each 1,000 cubic yards of fill, whichever requires the greater number of tests.
Any cleanouts and processed ground to receive fill must be observed by the soils engineer and/or engineering geologist prior to any fill placement. The contractor shall notify the geotechnical engineer when these areas are ready for observation.
PROTECTION OF WORK
During the grading process and prior to the complete construction of permanent drainage controls, it shall be the responsibility of the contractor to provide good drainage and prevent ponding of water and damage to adjoining properties or to finished work on the site.
After the geotechnical engineer has terminated his observations of the completed grading, no further excavations and/or filling shall be performed without the approval of the soils engineer, if it is to be subject to the recommendations of this report. 102
APPENDIX E
UTILITY TRENCH BACKFILL GUIDELINES
103
APPENDIX E
UTILITY TRENCH BACKFILL GUIDELINES
The following guidelines pertinent to utility trench backfills have been adopted by the County of Orange, Environmental Management Agency Grading Section, effective March 31, 1986. The application of the guidelines is strictly enforced by the County reviewers and inspectors.
1. Each utility subcontractor (gas, electric, water, sewer, telephone, cable TV, irrigation, drainage, etc.) shall submit to the developer for dissemination to his consultants (civil engineer, geotechnical engineer, and utility contractor) a plot plan of all utility lines installed under his purview which identifies line type, material, size, depth, and approximate location.
2. The developer or his agent shall provide a composite plot plan of all utilities or a copy of all individual utility plot plans to his geotechnical engineer for use in evaluating whether all utility trench backfills are suitable for the intended use.
3. The geotechnical engineer shall provide the County with a report that includes a plot plan showing the location of all utility trenches, which:
A. Are located within the load influence zone of a structure (1:1 projection) B. Are located beneath any hardscape
C. Are parallel and in close proximity to the top or toe of a slope and may adversely impact slope stability if improperly backfilled
D. Are located on the face of a slope in a trench 18 inches or more in depth.
Typically, trenches that are less than 18 inches in depth will not be within the load influence zone if located next to a structure and will not have a significant effect on slope stability if constructed near the top or toe of a slope, and need not be shown on the plot plan unless determined to be significant by the geotechnical engineer. This plot plan may be prepared by someone other than the soil engineer, but it must meet his approval.
4. Backfill compaction test locations must be shown on the plot plan described in No. 3 above, and a table of test data provided in the geotechnical report.
5. The geotechnical report (utility trench backfill) must state that all utility trenches within the subject lots have been backfilled in a manner suitable for the intended use. This includes the backfill of all trenches shown on the plot plan described in No. 3 and the backfill of those trenches that did not need to be plotted on this plan. 104
APPENDIX F
MAINTENANCE OF HILLSIDE HOME SITES
105
APPENDIX F
MAINTENANCE OF HILLSIDE HOME SITES
Sites graded in hillsides require maintenance and repair of slopes and drainage. The City of Los Angeles, Department of Building and Safety has published a Homeowner's Guide (June 1974) containing "Recommendations for Maintenance of Graded Sites," which are pertinent to all graded sites:
"It is incumbent upon the hillside property owner to maintain his property in a manner which will assure the continued stability of the property. The following are recommendations regarding slope and yard maintenance in graded hillside areas:
1. Maintain existing slope planting, provide new approved planting where indicated, and maintain irrigation systems in working order.
2. Maintain paved diverter terraces, interceptor terraces, downdrains, appurtenances such as inlets, and velocity reducer structures in a clean condition and in good repair.
3. Earth berms prevent water from flowing over the slope. It is important that these berms be maintained.
4. Standing storm water on the pad area directly above the descending slopes, whether natural, cut, or fill, is a major contributor to slope failure. It is important that the pad drainage be maintained at a minimum of 2 percent to the street or other approved location to prevent this situation.
5. Side swales, which direct water around the house, should be maintained so that they will not become ineffective.
6. Catch basins, grates, and subsurface drainage piping should be kept free of silt and debris.
7. Roof gutters and downspouts should be inspected periodically to ensure that they are not broken or clogged. All non-erosive drainage devices should be kept clean and in good repair.
8. Extensive landscaping or revision to the property may seriously alter the surface drainage pattern. When landscaping, homeowners should avoid disrupting flow patterns created when the property was originally graded. It should be remembered that normal property drainage in hillside areas is from the rear yard to the street. Some properties drain to natural water courses.
9. Any problems, such as erosion, should be repaired immediately in order that more serious problems may be averted.
10. Rodent activity should be controlled to prevent water penetration and loosening of the soil.
11. Care should be exercised to prevent loose fill from being placed on a grading site, especially on slopes."
106
107