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HomeMy WebLinkAboutPA2022-0315_20230328_Preliminary Geotech Investigation 12-06-22 December 6, 2022 Blues 1905, LLC Project No: 72681-00 c/o Wealthgate Family Office Report No: 22-9231 5025 Pearl Parkway Boulder, Colorado 80301 Attention: Ms. Lynnette Miscio Executive Administrator Subject: Updated Preliminary Geotechnical Investigation Proposed Remodel and Additions to Single-Family Residence 2741 Ocean Boulevard Corona del Mar, California INTRODUCTION This report presents updated results and recommendations of a preliminary investigation undertaken to relate onsite and certain regional geotechnical conditions to the proposed construction of remodel improvements to the existing single-family residence at the subject site. Analysis for this investigation is based upon the conceptual architectural plans prepared by Evens Architects of the KAA Design Group and our previous onsite work (Appendix A, Reference 16). The conclusions and recommendations of this report are considered preliminary as they precede the development of grading and foundation plans, the formulation of which are partially dependent upon the recommendations presented herein. Scope of Investigation The investigation included the following: 1. Review of our previous onsite report as well as other pertinent geotechnical literature, including certain regional and site specific reports and maps, and interpretation of aerial photographs. 2. Geologic surface reconnaissance of the property and surrounding areas. 3. Preparation of an updated geotechnical plot plan and cross sections relating the known site conditions to the proposed construction and depicting certain geotechnical recommendations for site development. 4. Geotechnical analysis of subsurface conditions as related to shoring and foundation design, and construction recommendations. December 6, 2022 Project No: 72681-00 Report No: 22-9231 Page No: 2 5. Preparation of this geotechnical report presenting updated conclusions and recommendations for site development in accordance with the 2019 California Building Code and for use by your design professionals, contractors, and submittal to the City of Newport Beach. Accompanying Illustrations and Appendices Figure 1 - USGS Geologic Location Map Figure 2 - CDMG Seismic Hazards Index Map Figure 3 - Typical Retaining Wall Subdrain Detail Figure 4 - Typical Subdrain for Caisson Retaining Wall Figure 5 - Typical Slab Subdrain Detail Appendix A - References Appendix B - Previous Core Logs Appendix C - Previous Field Exploration and Laboratory Testing Appendix D - Slope Stability and Wall Loading Analyses Appendix E - Standard Grading Specifications Appendix F - Utility Trench Backfill Guidelines Plate 1 - Updated Geotechnical Plot Plan Plate 2 - Updated Geotechnical Cross Sections B-B’, C-C’, and D-D’ Site Description The subject property is located on the southwestern-facing slope in the southwestern portion of the community of Corona del Mar in Newport Beach, California. The property is flanked to the east by Ocean Boulevard, to the north by an adjacent residence, to the south by open space, and to the west by Way Lane and Shell Street. The property was previously developed with a circa 1960’s, 4,500 square foot single-family home and associated improvements. A portion of the existing residence and improvements will be removed, with the exception of the floors and foundation. Topographically, the lot can be characterized as a 0.25 acre westerly-sloping parcel descending 65+ feet at a slope ratio of approximately 1.3:1 (horizontal: vertical). Total relief across the site is from a maximum elevation of 70+ feet at Ocean Boulevard, to 11+ feet on Way Lane. Proposed Construction Our review of conceptual architectural plans dated September 26, 2022 prepared by Evens Architects of the KAA Design Group indicates the proposed development generally is planned to consist of a mixed height, maximum five-story single-family residence built within the notched- space in the sloping lot. The lower structure will be supported on a mat foundation and with a perimeter retaining wall system. Upper portions may be supported on caissons. December 6, 2022 Project No: 72681-00 Report No: 22-9231 Page No: 3 The existing lower-level multi-car garage will remain at the Way Lane grade, and provide support for the new and existing upper levels. Proposed floor level elevations range from 11.3 feet to 60.5 feet. The approximately 8,292± square feet home is envisioned to consist of steel and wood frame construction. The structure is to be supported by a mat and retaining wall foundation founded on bedrock with limited concrete caissons into bedrock for the western edge. Slopes will remain after development ranging from 13 to 40± feet high. Existing slope ratios range from 1.25-1.5 to 1 (horizontal to vertical). Shoring wall systems to a maximum height of 45± feet will be required along the north, south, and east adjoining property lines. GEOTECHNICAL CONDITIONS Geologic Setting The property is situated at the seaward boundary of a regionally extensive marine terrace that lies at the coastal margin of the San Joaquin Hills. The marine terrace was developed as a wave cut platform and, in the site vicinity, is underlain by sedimentary bedrock strata that were uplifted in the geologic past by tectonic forces acting on this region of southern California. Regionally, the bedrock is unconformably overlain by marine terrace deposits (ancient beach deposits). Marine and subaerial erosion of this terrace during recent geologic time has created the marine terrace surface, bluff and bayside that forms the property. Earth Materials The site is underlain at shallow depth by sedimentary bedrock classified as a part of the Monterey Formation. The bedrock is locally overlain in the eastern portion of the property by marine terrace deposits, and localized deposits of fill from the original construction. As locally exposed on the property and on the point on the western edge of Corona del Mar State Beach, the bedrock is primarily very hard and locally cemented sandstone and siltstone, with locally interbedded shale. This rock is typically hard and reduces into gravel to cobble-sized fragments. Marine terrace deposits typically consist of silty medium-grained sand with varying proportions of pebbles, gravel, and cobbles as a basal lag. This deposit reflects the ancient shoreline and beach depositional environment directly overlying the bedrock scour. The deposits are commonly dense and competent, but are prone to caving and raveling in unsupported, steep- walled excavations, or in borings with groundwater. The bedrock deposits are suitable for support of all new construction. Terrace deposits are suitable for support of landscape elements such as exterior flatwork and site walls. Based upon current and previous laboratory testing, onsite materials have a very low to medium expansion potential, a negligible concentration of soluble sulfates, and a moderate degree of corrosivity to buried metals. The majority of the bedrock materials should excavate, but with difficulty, with conventional grading equipment in good repair. Drilling and deep cuts into hard bedrock will be very difficult and may generate oversized rock. December 6, 2022 Project No: 72681-00 Report No: 22-9231 Page No: 4 Geologic Structure Based on regional maps and observations of nearby exposures, the bedrock strata underlying the site and vicinity are variably folded with a general northwesterly strike and southwesterly dip. This orientation reflects an obliquely unsupported structural-topographic relationship. However, well cemented character of the rock with the variably folded strata generally favors gross slope stability. Fracturing within the formation is also variable and will require lagging on vertical cuts to maintain stability. Slope Stability No evidence of former gross instability affecting the site has been observed based upon site review. Interpretation of pre-development aerial photographs reveals no geomorphic features suggestive of previous gross slope or former deep instability. Future slope instability is considered unlikely, as the development will accommodate grade changes with engineered retaining walls. No permanent cut or fill slopes are depicted in the proposed plans. The natural slopes anticipated to remain to the east and upslope of the development area are low height. Foundations in these areas should have slough walls for debris collection. Groundwater Perched groundwater can occur at shallow depth within the terrace deposits and at the terrace- bedrock contact. Groundwater seepage in the terrace materials may present a construction constraint from caving. Groundwater is not anticipated to adversely affect the proposed residence provided proper subsurface and surface drainage is incorporated into design and construction, where required. Surficial Runoff Drainage from the property is generally toward the lower Way Lane. Proposed development should incorporate engineering and landscape drainage designed to minimize the potential of erosive discharge onto slopes or ponding of water adjacent to foundation elements. Surface drainage design is a matter that is deferred to a licensed civil engineer. Seismic Considerations Published Studies One of the principals of seismic analyses and prediction is the premise that earthquakes are more likely to occur on geologically younger faults, and less likely to occur on older faults. For many years studies have described faults with Holocene movement (within the last 11,700 years) as December 6, 2022 Project No: 72681-00 Report No: 22-9231 Page No: 5 “Active”, and faults with documented Pleistocene movement (within the last 1.6 million years) and with undetermined Holocene movement as “Potentially Active”. Informally, many studies have described faults documented to have no Holocene movement as “Inactive”. Recent geologic and seismic publications are attempting to clarify the nomenclature describing faults to represent the potential affects more accurately 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 1.6 million years Quaternary Undifferentiated Pre-Quaternary Before the last 1.6 million years It is important to note these categories embrace all Pre-Holocene faults as Potentially Active and provide no methodology to designate a given fault as “Inactive”. Although the likelihood of an earthquake or movement to occur on a given fault significantly decreases with inactivity over geologic time, the potential for such events to occur on any fault cannot be eliminated within the current level of understanding. Local and Regional Faults The closest published active fault to the site is the offshore extension of the Newport-Inglewood Fault Zone, approximately 1.1 miles west-southwest, (CGS/2004). Other active faults in the vicinity of the site include the San Joaquin Hills fault, approximately 7.2 miles from the site, the Palos Verdes Fault, approximately 13.8 miles to the northwest; the Whittier-Elsinore Fault, approximately 23.9 miles northeast, and the San Andreas Fault, approximately 52.5 miles to the northeast. The offshore portion of the Newport-Inglewood Fault zone is indicated in published reports as being a Potentially Active and Quaternary fault, (Jennings, C.W., et. al.; 2015). This interpretation is not universally shared, as this portion of the Newport-Inglewood Fault is considered by some to be a likely active feature. With the fault’s location approximately 1.1 miles to the west and 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. December 6, 2022 Project No: 72681-00 Report No: 22-9231 Page No: 6 The California Geological Survey includes the “San Joaquin Hills” blind thrust fault, theorized to exist from Newport Beach to Dana Point, and ramping up inland to the Irvine area, and essentially underlying the site. With earthquakes of significant magnitude (M6.6) presently postulated for this structure, it is calculated as the most significant seismic source to affect this site. Historic Ground Motion Analyses Utilizing attenuation relationships, one can estimate the ground motion history of the site and attempt to predict the probability of future accelerations within a given period of time. The study indicates the maximum site acceleration from 1800 to 2022 occurred during a magnitude 6.3 Long Beach Earthquake approximately 10 to 12 miles from the site on March 11, 1933. The California Integrated Seismic Network has completed an earthquake planning scenario for an M6.9 event on the Newport-Inglewood Fault Zone similar to the Long Beach event (https://www.cisn.org/shakemap/sc/shake/Newport_Inglewood6.9_se/pga.html). The maximum anticipated ground acceleration near the project site is between approximately 0.35g and 0.43g It is noted that the estimation of peak ground accelerations presented above is provided for the interest of the client and is required by local (City or County) review agencies. Seismic parameters for use by the structural engineer in accordance with the 2019 California Building Code in design of the proposed structure(s) are presented in the recommendations portion of this report. Site Classification for Seismic Design For the purposes of determining seismic design parameters provided in the Recommendations portion of this report pertaining to the new structures, the upper one hundred feet of soil underlying the subject site has been classified in accordance with Chapter 20 of the ASCE/SEI 7- 16. Given the results of our field investigation and our review of conceptual development plans, which indicates the new residence will be supported in moderately to strongly cemented bedrock, the site classifies as B. Site classification as specified above is based on the procedures outlined in Section 20.3.4 of the ASCE/SEI 7-16, which states that shear-wave velocities for bedrock may be estimated by the Geotechnical Engineer or Engineering Geologist. As such, the cemented Monterey Formation bedrock underlying the proposed residence is estimated to have shear wave velocities between 2,500 ft/sec to over 5,000 feet/sec. Secondary Seismic Hazards Review of the Seismic Hazards Zones Map (CDMG, 1998) for the Newport Beach Quadrangle, Figure 2, indicates the site may be located within a zone of required investigation for earthquake December 6, 2022 Project No: 72681-00 Report No: 22-9231 Page No: 7 induced landslides and adjacent to a zone mapped for liquefaction. As proposed development will be founded on competent bedrock and effectively remove the majority of the existing slope, the possibility of seismic landsliding or liquefaction to impact the property or improvements is considered remote. Other secondary seismic hazards to the site include deep rupture, shallow ground cracking, and settlement. With the absence of active faulting onsite, the potential for deep fault rupture is not present. The potential for shallow ground cracking to occur during an earthquake is a possibility at any site, but does not pose a significant hazard to site development. The potential for seismically induced settlement to occur is considered nil for the bedrock site. The potential for tsunami inundation of the garage although possible, is considered to be low given the planned residence floor elevations. CONCLUSIONS 1. Proposed development is considered feasible from a geotechnical viewpoint provided the recommendations of this report are followed during design, construction, and long-term maintenance of the subject property. Proposed development should not adversely affect adjacent properties, provided appropriate engineering design, construction methods, and care are utilized during construction. 2. The property is underlain at shallow depth predominantly by Monterey Formation material. The bedrock is overlain along the front (east, northeast, southeast) of the property by marine terrace deposits, and fill and beach sands are possible at the rear (west, northwest, southwest) of the property adjacent to Way Lane. 3. Onsite materials have a very low to medium expansion potential, negligible soluble sulfate concentrations with respect to concrete deterioration, and a “moderate” potential for corrosion of buried metal based upon previous and current laboratory testing. 4. 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. The potential for seismically induced liquefaction affecting the residence is considered nil. 5. Groundwater may be a construction and design nuisance. If present, groundwater will promote caving in caisson excavations. Suitable drainage elements need to be installed at shoring/retaining walls and beneath the lowest floor level to mitigate possible transient seepage conditions. 6. Adverse surface discharge onto or off the site is not anticipated provided proper engineering design and post-construction site grading are implemented. December 6, 2022 Project No: 72681-00 Report No: 22-9231 Page No: 8 7. The bedrock materials beneath the site are anticipated to remain grossly stable. Limited natural slopes will remain with the proposed development, and slough walls are recommended where improvements abut ascending natural slopes. 8. Excavations into the slope for proposed construction will be shored and supported by proposed caisson or soil nail/rock bolt systems, or a hybrid design. Terrace sands and fractured rock exposed within the gaps between shoring elements may locally be prone to caving and use of lagging is required. 9. Shallow bedrock materials should excavate with conventional earthmoving equipment; however, very difficult excavation of deeper drilling or cuts should be anticipated. Drilling conditions may be difficult due to hard rock. Limited excavation may require a hydraulic ram and chipping at depth. 10. Vibration monitoring of peak particle velocities during the demolition, drilling, and hard rock excavation is recommended. 11. The new portions of the proposed residence and exterior improvements should be supported by a mat foundation and caissons, in order to be founded entirely within bedrock materials. Lightly loaded exterior hardscape elements may be constructed on terrace materials or engineered fill. 12. Where existing foundations elements are to be used, the structural engineer should evaluate their capacity to support new loads utilizing the design criteria presented herein. Underpinning of existing foundation elements to derive support in bedrock may be necessary. 13. During a seismic event, the proposed foundation system supporting the addition(s) may perform differently than the foundation system for the existing residence. The structural engineer should evaluate the structural connections between the proposed and existing structures, and provide additional requirements, if warranted, to reduce the potential for distress along such structural connections. RECOMMENDATIONS Site Preparation and Grading 1. General Grading of the site should be performed in accordance with the Standard Grading Specifications of Appendix E. Excavations should be supervised and approved in writing by a representative of this firm. Grading will mostly include the excavation and export of earth materials to construct the cuts and building pad grades. Overcut or damaged December 6, 2022 Project No: 72681-00 Report No: 22-9231 Page No: 9 bedrock or terrace may require remedial grading, with up to 2+ feet of over-excavation and re-compaction required beneath improvements to achieve more uniform subgrade conditions. Locally deeper removals may be required as determined by the geologist during construction. 2. Removal of Existing Improvements Deleterious materials, including organic materials and trash, should be removed and disposed of offsite. 3. Compaction Standard Onsite soils are anticipated to be suitable for use as compacted fill, except for wall backfill. Materials should be placed at or near optimum moisture content and compacted under the observation and testing of the soil engineer. If adverse bedrock conditions are encountered, the over-excavated bedrock materials may be treated with 5 percent by weight cement to mitigate expansion potential. The recommended minimum density for compacted material is 90 percent of the maximum dry density as determined by ASTM D 1557-07. 4. Temporary Construction Slopes A. Protection of Property In order to reduce the potential risk to adjoining properties, construction cuts will require shoring. 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. The earth materials exposed in temporary excavations should be evaluated and classified by the contractor during construction. 5. Permanent Shoring It is anticipated that shoring will be used to accommodate site excavations and will be designed as a permanent retaining wall offset and separate from the proposed building wall. Shoring should consider topographic and structural surcharges of the adjacent properties. December 6, 2022 Project No: 72681-00 Report No: 22-9231 Page No: 10 Final selection of an appropriate system must include consideration of the potential effects of vibrations, caving, deflections, and footing area disturbance on the neighboring structures. Shoring may not be removed following construction as it will create void spaces. To reduce the risk of possible settlement induced distress on adjacent properties, shoring elements along property boundaries should be left in place. However, it should be recognized that vibrations induced by shoring installation alone may be sufficient to cause distress to nearby improvements. Vibration monitoring is recommended. Design lateral loading values for a cantilevered pile temporary shoring system should be based upon 40 pounds per cubic foot acting in a triangular distribution backing fill or terrace soils, and 10 pounds per cubic foot acting in a triangular distribution backing bedrock. Braced wall design should utilize a uniform pressure of 480 pounds per square foot backing fill or terrace soils, and a uniform pressure of 24H psf where H is in feet backing bedrock. Caissons should be designed as recommended below. Use 200 psf lagging loads. The placement of shoring should consider that construction may encounter variably loose zones which may be prone to settlement. It is the contractor’s responsibility to develop appropriate means and methods of construction to avoid damage to adjacent properties. Proper installation of shoring is the responsibility of the contractor. The adjacent property owners must be advised of the risks and the owner and builder should provide arrangements to repair any possible damages. Where shoring elements will become permanent, refer to the design criteria provided in the following sections of this report. Structural Design of Foundations and Slabs It is anticipated that foundation elements for the residence will bear in cemented Monterey formation bedrock and will utilize both a mat foundation and caissons. Mat foundations and slabs founded on such areas need not be designed to resist the effects of expansive soils. Foundations and slabs should be designed for the intended use and loading by the Structural Engineer. The design should consider the bedrock foundation design properties provided below. The distribution of earth materials is depicted on Plate 1, which may be utilized to assist in foundation design. Our recommendations are considered to be generally consistent with the standards of practice. They are based on both analytical methods and empirical methods derived from experience with similar geotechnical conditions. These recommendations are considered the minimum necessary for the likely soil conditions and are not intended to supersede the design of the Structural Engineer or criteria of governing agencies. December 6, 2022 Project No: 72681-00 Report No: 22-9231 Page No: 11 1. Mat Foundations Mat foundations should be designed in accordance with the 2019 California Building Code. The minimum recommended slab thickness is 18 inches, with No. 4 bars top and bottom at a spacing of 12 inches, placed in both directions. Mat foundations supported by competent bedrock may be designed for an allowable bearing value of 10,000 pounds per square foot with a minimum embedment of 12 inches below the lowest adjacent grade. The design value may be increased one-third for short duration wind or seismic loading. A subgrade modulus of 500 pounds per cubic inch may be used in design. Total and differential settlements are anticipated to be on the order of 1/2+ and 1/4+ inch, respectively, over a distance of 20 feet. Actual foundation embedment should be governed by CBC requirements and the structural engineering design. Lateral loads may be resisted by earth pressure forces on the side of the mat foundation and by friction acting on the bottom of the mat slab. The allowable passive pressure forces may be computed using an equivalent fluid density of 400 pounds per cubic foot, and a coefficient of friction of 0.4 may be used in computing the frictional resistance. Friction resistance and passive pressure may be combined without reduction. 2. Pre-Wetting of Mat Slab Subgrade Pre-wetting of the mat slab subgrade at or above optimum moisture content should be performed just prior to slab construction. 3. Existing Foundation Underpinning Deepened/caisson foundations embedded 2 feet or more into competent bedrock material may be designed for an allowable bearing value of 4,000 pounds per square foot. Lateral resistance may be calculated utilizing 150 and 400 pounds per cubic foot equivalent fluid pressure for beach deposits and competent bedrock, respectively, acting on a tributary area of twice the caisson diameter. If deepened footings are utilized, the minimum width of 18 inches is recommended and lateral loads may be resisted by passive pressure forces and friction acting on the bottom of footings. The allowable passive pressure may be computed using an equivalent fluid density of 400 pounds per cubic foot for bedrock up to a maximum of 4,000 pounds per square foot. A coefficient of friction of 0.4 may be used in computing the frictional resistance in bedrock. Friction resistance and passive pressure may be combined without reduction. December 6, 2022 Project No: 72681-00 Report No: 22-9231 Page No: 12 4. Caissons Caissons required for shoring or foundations should be designed for a minimum of 10 feet embedment into bedrock. Caissons may be designed for a dead plus live load end bearing value of 15,000 pounds per square foot for 10 feet minimum bedrock embedment. A skin friction of 500 pounds per square foot within the bedrock may also be utilized. Lateral resistance may be calculated utilizing 500 pounds per cubic foot equivalent fluid pressure, acting on a tributary area of twice the caisson diameter (D) provided caissons are spaced at least 2D center-to-center. A maximum lateral value of 10,000 pounds per square foot should be used. Caisson fixity may be taken at a bedrock embedment of 2 feet. 5. Slab Subdrains or Waterproofing Percolating irrigation and meteoric water may perch on top of less pervious earth materials (bedrock) beneath the site. Groundwater effects on the lowest level construction can be reduced by intercepting the groundwater with a subdrain system constructed beneath the slab(s). If utilized, the subdrain system should be constructed in accordance with the detail presented on Figure 5, and the information provided below. As a minimum, mat slabs should be underlain by 4 inches of ½ to ¾ inch open graded gravel. Slabs should also 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. The slab subdrain system should consist of 4-inch diameter perforated pipe graded to flow at one percent in the base of 12-inch deep trench around the perimeter of the slab and spaced in a 10 feet grid pattern within the interior. The trench should be lined with non-woven filter fabric and backfilled with ½ or ¾ inch rock. The slab subdrain piping system should be outletted per the Civil Engineer. As an alternative to the suggested slab subdrain system shown in Figure 5, the lower slab may be waterproofed. Slab waterproofing design and details should be provided by the project architect or waterproofing consultant. Structural Design of Retaining Walls 1. Lateral Loads Lateral earth pressures for design are determined using Generalized Limit Equilibrium (GLE) method. Our calculations for site stability and wall pressures are included in Appendix D. Active pressure forces acting on retaining walls which support onsite bedrock material or onsite terrace and fill material may be computed based on equivalent fluid pressures of 10 December 6, 2022 Project No: 72681-00 Report No: 22-9231 Page No: 13 and 40 pounds per cubic foot, respectively. At-rest pressure forces on restrained walls supporting onsite bedrock material or onsite terrace material may be computed based on equivalent fluid pressures of 15 and 60 pounds per cubic foot, respectively. Other topographic and structural surcharges should be addressed by the structural engineer. Limited wall deformations normally occur and should be considered in design of finished surfaces. Seismic earth pressure loads for retaining walls are zero based on our GLE analyses (see Appendix D). Wall loading is controlled by static conditions. 2. Subdrains The drainage scheme depicted on Figure 3 or 4, or an approved alternative, should be used to achieve control of seepage forces behind retaining walls. Retaining walls incorporating shoring and shotcrete will likely utilize miradrain panels placed against the excavation backcut, as generally depicted on Figure 4. The details of such subdrain systems are referred to the wall designer, builder, or waterproofing consultant. The subdrain is not a substitute for waterproofing. 3. Waterproofing Waterproofing should be installed in accordance with the architects’ specifications or those of a waterproofing consultant. 4. Wall Deformation Use of a structural foam product such as Insulfoam should be considered for use between the shoring/retaining wall and building wall to allow for shoring/retaining wall deformations, while mitigating effects of these wall deformations on the building. This product has been used to limit loads on retaining walls because of its low unit weight (3 pcf) and load-deformation properties. Structural Design of Soil Nail (Optional) In view of the capacity envisioned for the anchors, we recommend that the design include gravity grouting throughout the entire length of the soil nail. An ultimate bond stress of 20 pounds per square inch may be used in the preliminary design for gravity-grouted anchors between the Monterey formation bedrock and the grout. Soil nails should have a typical maximum spacing of 5 feet with a minimum 6-inch diameter. The soil nail anchors should be inclined downward at a nominal 15-20 degrees from horizontal. The soil nails should be extended beyond the potential active wedge in order to derive their December 6, 2022 Project No: 72681-00 Report No: 22-9231 Page No: 14 resistance from beyond this potential failure plane. The anchors should have a minimum bond length of 5 feet. The actual bond length should be determined by the structural engineer. Considering the potentially corrosive nature of the onsite soil and bedrock materials, we recommend that, at a minimum, all permanent anchors be epoxy-coated. It is recommended that a concrete expert be retained to design an appropriate grout mix. In lieu of retaining a concrete expert, the 2019 California Building Code, Section 1904.1 should be utilized, which refers to ACI 318, Table 4.3.1. In addition, it is our recommendation that all anchor blocks and anchorages for permanent anchors be properly sealed against corrosion. The length of drilled hole should be verified and recorded by our firm. Grout should be injected at the low end of the drilled hole and should fill the drilled hole with a dense grout free of voids or inclusion of foreign material. Cold joints should not be used in grout placement. Soil nails should be grouted full length. After placing the grout for soil nails, they should remain undisturbed for the appropriate cure time. Nail lengths, reinforcement and connection details should be in accordance with the recommendations of the structural engineer. Hardscape Design and Construction Hardscape improvements along the front and rear of the residence may utilize conventional foundations and slabs in compacted fill. Such improvements should be designed in accordance with the foundation recommendations presented below. 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, and pre-soaking of subgrade soils as methods of minimizing 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. Planters, fences, garden walls and retaining walls constructed with a minimum embedment of 18 inches in compacted fill or competent terrace deposits should be designed for an allowable bearing value of 1,500 pounds per square foot, and may utilize an allowable lateral bearing pressure of 150 pounds per cubic foot and a friction coefficient of 0.25. Concrete flatwork should be divided into as nearly square panels as possible. Flatwork elements should be a minimum 5 inches thick (actual) and reinforced with No. 4 bars spaced at 16 inches on center both ways. Joints should be provided at maximum 8 feet intervals to give articulation to the concrete panels. Landscaping and planters adjacent to concrete flatwork should be designed in such a manner as to direct drainage away from concrete areas to approved outlets. December 6, 2022 Project No: 72681-00 Report No: 22-9231 Page No: 15 Planters located adjacent to principle foundation elements should be sealed and drained; this is especially important if located upon retaining wall backfills. Concrete Laboratory test results from onsite and nearby soils indicate onsite materials have negligible soluble sulfate content. It is recommended that a concrete expert be retained to design an appropriate concrete mix to address soil soluble sulfate content as well as the structural requirements. In lieu of retaining a concrete expert, it is recommended that the 2019 California Building Code, Section 1904.1 be utilized, which refers to ACI 318, Tables 4.3 and permits Type II cement. Corrosivity Onsite soils have a moderate potential for corrosion of buried metals. A corrosion expert should be retained to advise on appropriate mitigation and/or material selection. Seismic Structural Design Based on the geotechnical data and site parameters, the following is provided by the USGS (ASCE/SEI 7-16) to satisfy the 2019 CBC design criteria: Table 2, Site and Seismic Design Criteria For ASCE/SEI 7-16 and 2019 CBC Design Parameters Recommended Values Site Class Site Longitude (degrees) Site Latitude (degrees) Ss (g) B S1 (g) B SMS (g) B SM1 (g) B SDS (g) B SD1 (g) B Fa Fv PGAM (g) Seismic Design Category B -117.8779 33.5959 1.363 0.483 1.363 0.387 0.818 0.258 0.9 0.8 0.537 D December 6, 2022 Project No: 72681-00 Report No: 22-9231 Page No: 16 Finished Grade and Surface Drainage Finished grades should be designed and constructed so that no water ponds in the vicinity of footings or the rear slope. Drainage design in accordance with the 2019 California Building Code, Section 1804.4 is recommended. Roofs should be guttered and discharge conducted away from the house in a non-erosive manner as specified by the project civil engineer or landscape architect. Proper interception and disposal of onsite surface discharge is presumed to be a matter of civil engineering or landscape architectural design. The site is geotechnically unsuitable for the local discharge of onsite storm water due to onsite sloping conditions and the potential to adversely promote shallow groundwater conditions affecting nearby properties. Onsite discharge of storm water is not recommended. Foundation Plan Review In order to review the plans for conformance with the recommendations of this report and as a condition of the issue of this report, the undersigned should review final foundation plans and specifications prior to submission of such to the building official for issuance of permits. Such review is to be performed only for the limited purpose of checking for conformance with the design concept and the information provided herein. This review shall not include review of the accuracy or completeness of details, such as quantities, dimensions, weights or gauges, fabrication processes, construction means or methods, coordination of the work with other trades or construction safety precautions, all of which are the sole responsibility of the Contractor. Geofirm’s review shall be conducted with reasonable promptness while allowing sufficient time in our judgment to permit adequate review. Review of a specific item shall not indicate that Geofirm has reviewed the entire system of which the item is a component. Geofirm shall not be responsible for any deviation from the Construction Documents not brought to our attention in writing by the Contractor. Geofirm shall not be required to review partial submissions or those for which submissions of correlated items have not been received. Observation and Testing The 2019 California Building Code (CBC), 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 detailed inspection of the Contractor’s work but rather are to allow Geofirm, as an experienced December 6, 2022 Project No: 72681-00 Report No: 22-9231 Page No: 17 professional, to become generally familiar with the work in progress and to determine, in general, if the work is proceeding in accordance with the recommendations of this report. Geofirm shall not supervise, direct, or have control over the Contractor’s work nor have any responsibility for the construction means, methods, techniques, sequences or procedures selected by the Contractor nor the Contractor’s safety precautions or programs in connection with the work. These rights and responsibilities are solely those of the Contractor. Geofirm shall not be responsible for any acts or omission of the Contractor, subcontractor, any entity performing any portion of the work, or any agents or employees of any of them. Geofirm does not guarantee the performance of the Contractor and shall not be responsible for the Contractor’s failure to perform its work in accordance with the Contractor documents or any applicable law, codes, rules, or regulations. These observations are beyond the scope of this investigation and budget and are conducted on a time and material basis. The responsibility for timely notification of the start of construction and ongoing geotechnically involved phases of construction is that of the Owner and his Contractor. Typically, at least 24 hours’ notice is required. Jobsite Safety Neither the professional activities of Geofirm, nor the presence of Geofirm’s employees and subconsultants at a construction/project site, shall relieve the General Contractor of its obligations, duties and responsibilities including, but not limited to, construction means, methods, sequence, techniques or procedures necessary for performing, superintending and coordination the work in accordance with the contract documents and any health or safety precautions required by any regulatory agencies. Geofirm and its personnel have no authority to exercise any control over any construction contractor or its employees in connection with their work or any health or safety programs or procedures. The General Contractor shall be solely responsible for jobsite safety. LIMITATIONS This investigation has been conducted in accordance with generally accepted practice in the engineering geologic and soils engineering field. No further warranty is offered or implied. Conclusions and recommendations presented are based on subsurface conditions encountered and are not meant to imply a control of nature. As site geotechnical conditions may alter with time, the recommendations presented herein are considered valid for a time period of one year from the report date. The recommendations are also specific to the current proposed development. Changes in proposed land use or development may require supplemental investigation or recommendations. Also, independent use of this report in any form cannot be approved unless specific written verification of the applicability of the recommendations is obtained from this firm. December 6, 2022 Project No: 72681-00 Report No: 22-9231 Page No: 18 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 D. Bearfield, P.E Chief Engineering Geologist, E.G. 1619 Associate Engineer, P.E. 84335 Date Signed: 12/6/2022 KAT/JDB:mr Distribution: Addressee Via Email JOB NO.:DATE:FIGURE: USGS Geologic Location Map, Santa Ana 30' x 60' Quadrangle 72681-00 December 2022 1 SITE 2741 Ocean Blvd. Corona del Mar JOB NO.:DATE:FIGURE: CDMG Seismic Hazards Map, Newport Beach and Laguna Beach Quadrangles 72681-00 December 2022 2 SITE 2741 Ocean Blvd Corona del Mar JOB NO.:DATE:FIGURE: Typical Retaining Wall Subdrain Detail 72681-00 December 2022 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 fabric- wrapped 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. 12"-18" Finish Grade -Design May Vary per Architect or Civil Engineer Alternative Weep Hole(s) for Exterior Applications, Design per Architect or Civil Engineer JOB NO.:DATE:FIGURE: Typical Subdrain for Caisson Retaining Wall 72681-00 December 2022 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 JOB NO.:DATE:FIGURE: Typical Slab Subdrain Detail 72681-00 December 2022 5 Concrete Slab 4" Gravel Layer Single Sized 1/2 to 3/4-inch Drain Rock 15-mil visqueen membrane overlaying gravel Native Soil or Engineered Fill Geotextile Filter Fabric Perforated 4" PVC Schedule 40 Drain Pipe 12" min 12" min APPENDIX A REFERENCES APPENDIX A REFERENCES 1. Anderson, Donald G., et al., 2008, NCHRP Report 611, Seismic Analysis and Design of Retaining Walls, Buried Structures, Slopes and Embankments,” Transportation Research Board, Washington, D.C. 2. 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. 3. Building Seismic Safety Council, 2009, NEHRP Recommended Seismic Provisions for New Buildings and Other Structures, FEMA, Washington, D.C. 4. California Building Code, 2019 Edition. 5. California Division of Mines and Geology, 1998, “Seismic Hazards Zones Map, Laguna Beach Quadrangle. 6. California Division of Mines and Geology, 1998, “Seismic Hazards Zones Map, Newport Beach Quadrangle. 7. California Geological Survey, 2008, “Guidelines for Evaluating and Mitigating Seismic Hazards in California,” Special Publication 117A. 8. Cao, T., Bryant, W.A., Rowshandel, B., Branum, D. and Wills, C.J., 2003, “The Revised 2002 California Probabilistic Seismic Hazard Maps, dated June. 9. Geofirm, 1995 "Preliminary Geotechnical Investigation, Proposed Duplex, 3016 Breakers Drive, Corona del Mar, California," Project No. 70533-00, Report No. 5-1823, dated January 10. 10. Geofirm, 1998, “Preliminary Geotechnical Investigation for Foundation Design, 231 and 233 Jasmine, Corona del Mar, California”; Project No: 70911-00, Report No. 8-2829, dated June 12. 11. Geofirm, 1999, “Preliminary Geotechnical Investigation, Proposed Single Family Residence, 3030 Breakers Drive, Corona del Mar, California”; Project No: 70998-00, Report No: 9-3124, dated June 4. 12. Geofirm, 2001, “Preliminary Geotechnical Investigation for Foundation Design, Proposed Single Family Residence, 2724 Ocean Boulevard, Corona del Mar, California”; dated January 23, 2001, Project No. 71146-00, Report No. 01-3615. 13. Geofirm, 2005, “Preliminary Geotechnical Investigation, Proposed New Single-Family Residence, 3036 Breakers Drive, Corona del Mar, California”; Project No. 71563-00, Report No. 05-5595, dated July 6. 14. Geofirm, 2014, “2013 CBC Geotechnical Update Report, Proposed New Single-Family Residence, 3225 Ocean Boulevard, Corona del Mar, California”, Project No. 71862-01, Report No. 14-7447, dated August 19. 15. Geofirm, 2014, “Updated Geotechnical Recommendations for Project Design Revisions, Proposed New Single-Family Residence, 3235 Ocean Boulevard, Corona del Mar, California”, Project No. 71879-03, Report No. 14-7479, dated May 21. 16. Geofirm, 2015, “Preliminary Geotechnical Investigation, New Single-Family Residence, 2741 Ocean Boulevard, Corona del Mar, California”, Project No. 72182-00, Report No. 15- 7693R, dated June 30. 17. Geofirm, 2020, “Updated Preliminary Geotechnical Investigation, New Single-Family Residence, 2741 Ocean Boulevard, Corona del Mar, California”, Project No. 72182-00, Report No. 15-7693R, dated June 30. 18. Jennings, Charles W., et al, 2015, “Fault Activity Map of California”, California Geological Survey, Digital Geologic Data Map No. 6. 19. Martin, G.R. and Lew, M.; 1999, “Recommended Procedures for Implementation of DMG Special Publication 117, Guidelines for Analyzing and Mitigating Liquefaction Hazards in California”, SCEC, dated March. 20. OSHPD/SEA, 2020, “Seismic Design Maps”, https://seismicmaps.org/. 21. United States Geological Survey, 2004, “Preliminary Digital Geologic Map of the Santa Ana 30’ x 60’ Quadrangle, southern California, Version 2.1”. APPENDIX B PREVIOUS CORE LOGS Ground Elevation: Figure No.: CORE NO.:C-1 Description Project No.:72182-00 De p t h ( f e e t ) Gr a p h i c R e c o v e r y In t e r v a l Sa m p l e I n t e r v a l CORE LOG De p t h ( f e e t ) Ru n T i m e ( m i n ) Ph o t o I D 8" dia. HSA & Core Gregg Drilling Method of Drilling: Drilling Company: RQ D ( % ) Bo x N u m b e r Re c o v e r y ( % ) 4/27/2015 ERH 2741 Ocean Blvd, Corona del Mar Date(s) Logged: Logged By: LOCATION: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 0-23':Marine Terrace Deposits –Variably silty fine to medium SAND, local fine gravel; weakly cemented, medium dense, yellowish to orangish brown. 80 NA 122517122521 122534122539 NA 92 67 135730 135732135735 135738135743 135754 1 5:15 12:20 @5’: Cal-sampled in adjacent hand-auger boring; sample is dry to damp, weakly cemented slightly silty fine SAND. @20-25': From 20'-23'sample consist of variably silty SAND with fine gravel lag deposits on contact. Bedrock at 23'. @25'-30': From 25'-27.8',sample consists of dark gray moderately cemented medium/coarse SANDSTONE, moderately fractured and washed-out. Siliceous/cherty layer approx 3" thick at 26.5'. From 27.8'-30',sample consists of thinly bedded to laminated SILTSTONE and CLAYSTONE, moderately soft, moderately to locallly strongly indurated, slightly fractured; generally gray with bands of light gray and orange. BLOWS70/6" (70lb) @23’-50': Bedrock: Monterey Formation –Moderately to strongly cemented SANDSTONE with thick interbeds of variably indurated laminated SILTSTONE-CLAYSTONE; bedrock portion of core sample consists of moderately cemented fine SANDSTONE; dark gray, slightly fractured. @5’-10': Slightly silty fine SAND with scattered shell fragments. 20 NA 114439 114442 NA5:00± 0 NA NA NA5:00± 63 52 132730132736 132740 113:30 93 73 142337 142339142351 142354 1 (30.3')13:00 97 52 144505 213:30 @30'-35': From 30'-31.5', sample consists of moderately cemented, slightly fractured, olive-brown sandy SILTSTONE. From 31.5'-35', sample consists of strongly cemented SANDSTONE, moderately hard, slightly fractured, gray. @35'-40': Strongly cemented,moderately hard SANDSTONE continues. 2 Core Logs.xlsx 5/14/2015 Geofirm 2741 Ocean Blvd, Corona del Mar Ground Elevation: Figure No.:Project No.:72182-00 CORE LOG 0 CORE NO.:C-1 De p t h ( f e e t ) Description De p t h ( f e e t ) Sa m p l e I n t e r v a l Gr a p h i c R e c o v e r y In t e r v a l Re c o v e r y ( % ) RQ D ( % ) Ru n T i m e ( m i n ) Ph o t o I D Bo x N u m b e r Date(s) Logged:4/27/2015 Method of Drilling:8" dia. HSA & Core Logged By:Drilling Company: LOCATION: ERH Gregg Drilling 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 Continued 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 Total Depth = 50' Backfilled with cuttings and bentonite chips Bedrock: Monterey Formation,continues 92 63 145033145035 145037145040 311:00 75*40*154710 154712 317:00 @40'-45': From 40'-43', strongly cemented, moderately hard SANDSTONE continues from above. From 43'-44.7', sample consists of thinly bedded to laminated, moderately indurated, moderately soft, olive brown and gray CLAYSTONE-SILTSTONE. Remainder of core sample consists of strongly cemented SANDSTONE. @45'-50': Disturbed core sample consists of thinly bedded to laminated, moderately indurated, moderately soft CLAYSTONE-SILTSTONE. Olive brown and gray. *Numbers may not be accurate due to difficult extraction process, which disturbed core sample. 2 (41.1') Core Logs.xlsx 5/14/2015 Stoney-Miller Consultants, Inc. Ground Elevation: Figure No.:Project No.:72182-00 CORE LOG CORE NO.:C-2 De p t h ( f e e t ) Description De p t h ( f e e t ) Sa m p l e I n t e r v a l Gr a p h i c R e c o v e r y In t e r v a l Re c o v e r y ( % ) RQ D ( % ) Ru n T i m e ( m i n ) Ph o t o I D Bo x N u m b e r Date(s) Logged:4/28/2015 Method of Drilling:8" dia. HSA & Core Logged By:ERH Drilling Company:Gregg Drilling LOCATION:2741 Ocean Blvd, Corona del Mar 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 0-23':Marine Terrace Deposits –Variably silty fine to medium SAND, local fine gravel; weakly cemented, medium dense, yellowish to orangish brown. NOTE: Casing advanced to 16' improve circulation and reduce occurrence of adjacent slope erosion or possible water intrusion on nearby improvements 73 65 130724 130726130729 130732130734 115:00± @20'-25': Coring effort significantly increased at 23', inferred bedrock contact. No recovery in core barrel, only in shoe, which contained laminated clayey SILTSTONE, light gray, orange and brown. @25'-30': Thinly bedded to laminated SILTSTONE and CLAYSTONE, moderately soft, slightly to moderately fractured; weathered, generally gray with bands of light gray and orange; core sample disturbed upon transfer to box. Siliceous/cherty layer approx 5" thick at 25'. @23’-50': Bedrock: Monterey Formation –Predominantly variably indurated laminated SILTSTONE-CLAYSTONE with minor thick interbeds of moderately to strongly cemented SANDSTONE. 33 0 130310 130313 115:00± 93 93 133350 133352133354 133356133358 1 (34.3')16:00± 97 73 135716135719 135721135723 135726135728 135733 218:00± @30'-35': From 30'-32', sample consists of thinly bedded to laminated SILTSTONE and CLAYSTONE continues from above. From 32'-35', sample consists of strongly indurated, moderately soft grayish brown SILTSTONE. @35'-40': From 35'-36', sample consists of strongly cemented,moderately hard SANDSTONE with closely spaced fractures; from 36' to 40', sample generally consists of moderately soft clayey SILTSTONE, orangish brown, slightly fractured. Contact between sandstone and siltstone is very steep, perhaps indicative of sandstone intrusion (dike). 2 @10'-15': Bulk Sample Core Logs.xlsx 5/14/2015 Geofirm 2741 Ocean Blvd, Corona del Mar Ground Elevation: Figure No.:Project No.:72182-00 CORE LOG 0 Ph o t o I D Bo x N u m b e r CORE NO.:C-2 De p t h ( f e e t ) Description De p t h ( f e e t ) Sa m p l e I n t e r v a l Gr a p h i c R e c o v e r y In t e r v a l Re c o v e r y ( % ) RQ D ( % ) Ru n T i m e ( m i n ) LOCATION: Date(s) Logged:4/28/2015 Method of Drilling:8" dia. HSA & Core Logged By:ERH Drilling Company:Gregg Drilling 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 Continued 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 Total Depth = 50' Backfilled with cuttings and bentonite chips Bedrock: Monterey Formation,continues 88 58 142750 142153142156 142158142200 142207 318:00± 100 48 144717 144719144722 144725144729 144733 317:00± @40'-45': From 40'-41.5', sample consists of strongly indurated/cemented,dark reddish gray sandy SILTSTONE with moderately spaced fractures (joints). From 41.5'-42.5', sample consists of moderately cemented sandy SILTSTONE, dark gray with white speckles. From 42.5'-44.5', sample consists of thinly bedded, strongly indurated/cemented SILTSTONE with widely-spaced, steeply dipping polished partings. @45'-50': Thinly bedded, strongly indurated/cemented SILTSTONE with widely-spaced, steeply dipping polished partings, continues from above. Weakly brecciated zone at 49'. 2 (42.9') Core Logs.xlsx 5/14/2015 Stoney-Miller Consultants, Inc. APPENDIX C PREVIOUS FIELD EXPLORATION AND LABORATORY TESTING APPENDIX C PREVIOUS FIELD EXPLORATION AND LABORATORY TESTING I. Field Exploration Procedures A. Field Exploration A track-mounted rotary wash drill rig with a 4-inch diameter face-discharge bit on a hollow stem drill rod was utilized to expose subsurface soils. B. Sampling 1. Core Samples Core samples of subsurface materials were obtained using 60-inch double tube coring barrel and wire line system. Soil and rock samples were cut and held in the inner barrel as the bit excavated the outer rock. NX-diameter cores were photographed and boxed onsite and transported to the laboratory for testing each day. Records of the core lengths and rock quality are documented on the core logs in Appendix B. 2. Disaggregated Sample Any bulk sample of material was bagged and transported to the laboratory for classification and physical testing. II. Laboratory Testing Procedures A. Moisture and Density Test The dry unit weight and field moisture content were determined for core specimens obtained from the test sampler by measuring the volume and weight of the specimen. The moisture determination was made in accordance with ASTM test methods. The results are provided in Figure C-1 and summarized on the boring logs in Appendix B. B. Corrosivity Series Soluble sulfates, pH and minimum resistivity were determined in accordance with California Test Method 417, ASTM D 4972, and California Test Method 643, respectively. The results are presented below: Sample Designation C-2 @ 10-15’ Soluble Sulfate - 41 mg/kg pH - 7.8 Minimum Resistivity - 2,560 ohm-cm (saturated) C. Maximum Density/Optimum Moisture Content The maximum dry density/optimum moisture content relationship was determined for a typical sample of the onsite soil. The laboratory standard used was ASTM: D 1557. The test results are presented below. Sample Location Maximum Density (pcf) Optimum Moisture Content (%) C-2 @ 10’ 122.5 9.0 D. Direct Shear A direct shear test was performed on representative remolded sample of the terrace soils. The sample was remolded to a dry unit weight of 107 pcf and moisture content of 7.6 percent. The tests were performed under nominal normal loads of 1000, 2000, and 4000 pounds per square foot at a strain rate of 0.065 inches per minute, and in general accordance with ASTM: D 3080. The test results are summarized in Figures C-4. E. Particle Size Analysis A particle size analyses was performed on representative sample of the on- site soils in accordance with ASTM D422. Test results are presented in Figure C-2. F. Unconfined Compression Tests Unconfined compressive strength tests were performed on eight samples of the bedrock material in accordance with ASTM D2938-95. The testing was completed at the laboratory of Leighton & Associates in Irvine, California. The results are presented on the attached Figure C-5. C-1 5.00 6 RING 3.9 111.7 21 C-1 20.00 60 RC C-1 25.00 60 RC C-1 30.00 60 RC C-1 35.00 60 RC C-1 40.00 60 RC C-1 45.00 60 RC C-2 10.00 60 LB C-2 25.00 60 RC C-2 30.00 60 RC C-2 35.00 60 RC C-2 40.00 60 RC C-2 45.00 60 RC Borehole Soil UnitSampleType DryDensity(pcf)Classification Expansion Index Water Content(%) MOISTURE, DENSITY AND SATURATION Depth(ft) SampleLength (in) Saturation (%) Client: Craig and Raquel Dawson Figure No. C-1 Project Number: 72182-00 Project Name: Dawson Address: 2741 Ocean Blvd;Corona del Mar 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 0.0010.010.1110100 COBBLES GRAVEL SAND D60 0.275 D100 BOREHOLE DEPTH finemedium 3 1002416301 200610501/2 50.20 HYDROMETERU.S. SIEVE OPENING IN INCHES U.S. SIEVE NUMBERS1.5 8 143/4 3/8 PE R C E N T F I N E R B Y W E I G H T PI Cc CuLLPL C-2 GRAIN SIZE IN MILLIMETERS coarse fine coarse SILT OR CLAY C-2 0.1329.5 Classification 140342040660 %Clay%Silt 9.811.478.6 %Sand%Gravel 0.2 D10 0.005 D30BOREHOLEDEPTH 11.57 GRAIN SIZE DISTRIBUTION 10.0 10.0 Client: Craig and Raquel Dawson Figure No. C-2 Project Number: 72182-00 Project Name: Dawson Address: 2741 Ocean Blvd;Corona del Mar 90 95 100 105 110 115 120 125 130 135 140 0 5 10 15 20 25 30 MOISTURE-DENSITY RELATIONSHIP DR Y D E N S I T Y , p c f WATER CONTENT, % Optimum Water Content Maximum Dry Density PCF % LL PL PI TEST RESULTS Test Method 2.80 2.70 2.60 Source of Material Description of Material ASTM D1557 Method A ATTERBERG LIMITS Curves of 100% Saturation for Specific Gravity Equal to: 122.5 9.0 C-2 @ 10 Client: Craig and Raquel Dawson Figure No. C-3 Project Number: 72182-00 Project Name: Dawson Address: 2741 Ocean Blvd;Corona del Mar 0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 0 1,000 2,000 3,000 4,000 DescriptionBOREHOLEDEPTH DIRECT SHEAR TEST NORMAL PRESSURE, psf SH E A R S T R E N G T H , p s f c 30 31 MC% C-2 C-2 10.0 10.0 Peak Strength Ultimate Strength 422 151 Client: Craig and Raquel Dawson Figure No. C-4 Project Number: 72182-00 Project Name: Dawson Address: 2741 Ocean Blvd;Corona del Mar APPENDIX D SLOPE STABILITY AND WALL LOADING ANALYSES APPENDIX D ENGINEERING ANALYSES GENERAL Engineering analyses were performed to assess the minimum Factors of Safety (FS) against future movement of the slope located within the subject property, and to assist in defining pressures on retaining walls. The analyses were performed with the actual or conservative geologic conditions. The “Slide 7.0”, 2D slope stability program utilized the stability analyses. The computer program utilizes the limit equilibrium theory for the calculation of the minimum Factory of Safety (FS). SHEAR STRENGTH PARAMETERS The shear strength parameters utilized in our engineering analyses are presented in Table D-1, below. These values were based on local experience in similar soils, laboratory test results by Stoney-Miller Consultants and others during previous investigations, and engineering judgment, and are considered reasonable and representative of the on-site materials. TABLE D-1 SUMMARY OF STRENGTH PARAMETERS Material Type Bulk Density (pcf) Cohesion C (psf) Friction Angle  (deg) Monterey Bedrock Along Bed Marine Terrace (Static) Marine Terrace (Seismic) Beach Deposits 135 120 120 115 5000 150 400 0 0 31 30 28 ANALYSES Engineering analyses were performed for a Cross Sections A-A’, B-B’ and C-C’ to assess gross stability and to estimate earth pressure loads. Analyses were performed with the proposed grades to determine remedial measures necessary to achieve the required factors of safety. The following conditions were evaluated: Potential wedge failures were made using GLE methods to assess lateral retaining wall loads for static and pseudostatic conditions as recommended by the NCHRP Report 611. Factors of safety of 1.0 were used for stability under both static and seismic conditions. The accelerations for seismic analyses were developed using a pseudo-static horizontal acceleration of 0.397g derived using two-thirds of the site PGAm of 0.596g as recommended in NEHRP Recommended Seismic Provisions, 2009 Edition, Commentary to Section 11.8.3. Gross stability was analyzed for both static and pseudo-static conditions. Given the competency of the terrace and underlying bedrock materials, required factors of safety were met for static and pseudo-static seismic conditions (see Table D-2). Sections were then analyzed for wedge surfaces through terrace soils and bedrock for static and seismic wall conditions. Factors of safety of 1.0 or more were achieved for trial surfaces using wall loads as presented in Table D-2. TABLE D-2 STABILITY ANALYSIS SUMMARY Section Static FOS Seismic FOS Figure No. Comments A-A’ 3.8 3.2 D-1.1 D-1.2 Proposed/Global Conditions, circular failure surfaces A-A’ 1.0 1.0 D-1.3 D-1.4 12-ft Wall Wedge Analysis with 25 pcf equivalent fluid pressure B-B’ 1.5 1.8 D-2.1 D-2.2 Proposed/Global Conditions, circular failure surfaces B-B’ 3.9 2.7 D-2.3 D-2.4 16-ft Wall Wedge Analysis with 0 pcf equivalent fluid pressure C-C’ 1.0 1.0 D-3.1 D-3.2 51-ft Wall Wedge Analysis with 20 pcf equivalent fluid pressure in upper terrace material Section Static FOS Seismic FOS Figure No. Comments D-D’ 1.0 1.4 D-4.1 D-4.2 33-ft Wall Wedge Analysis with 9 pcf equivalent fluid pressure in upper terrace material 3.83.8 400.00 lbs/ft2 200.00 lbs/ft2 200.00 lbs/ft2 0.00 lbs/ft2 300.00 lbs/ft2 3.83.8 RuWater  Surface Phi  (deg) Cohesion  (psf) Strength  Type Unit  Weight  (lbs/ft3) ColorMaterial  Name 0None31150Mohr‐ Coulomb120Qtm  Static 0None05000Mohr‐ Coulomb135Tm Safety Factor 0.0 0.3 0.5 0.8 1.0 1.3 1.5 1.8 2.0 2.3 2.5 2.8 3.0 3.3 3.5 3.8 4.0 4.3 4.5 4.8 5.0 5.3 5.5 5.8 6.0+ 80 60 40 20 0 -40 -20 0 20 40 60 80 100 Scenario Global/Static ConditionGroupXSA Company Geofirm/Stoney-Miller Consultants, Inc.Drawn By ZW Figure No.Figure D-1.1Date7/29/2020 Project Dawson Residence 2741 Ocean Boulevard, Corona del Mar, California SLIDEINTERPRET 9.008 3.23.2 400.00 lbs/ft2 200.00 lbs/ft2 200.00 lbs/ft2 0.00 lbs/ft2 300.00 lbs/ft2 3.23.2 RuWater  Surface Phi  (deg) Cohesion  (psf) Strength  Type Unit  Weight  (lbs/ft3) ColorMaterial  Name 0None30400Mohr‐ Coulomb120Qtm  Seismic 0None05000Mohr‐ Coulomb135Tm 0.15 Safety Factor 0.0 0.3 0.5 0.8 1.0 1.3 1.5 1.8 2.0 2.3 2.5 2.8 3.0 3.3 3.5 3.8 4.0 4.3 4.5 4.8 5.0 5.3 5.5 5.8 6.0+ 80 60 40 20 0 -40 -20 0 20 40 60 80 100 Scenario Global/Seismic ConditionGroupXSA Company Geofirm/Stoney-Miller Consultants, Inc.Drawn By ZW Figure No.Figure D-1.2Date7/29/2020 Project Dawson Residence 2741 Ocean Boulevard, Corona del Mar, California SLIDEINTERPRET 9.008 1.01.0 400.00 lbs/ft2 200.00 lbs/ft2 200.00 lbs/ft2 0.00 lbs/ft2 300.00 lbs/ft2 1.01.0 RuWater  Surface Phi  (deg) Cohesion  (psf) Strength  Type Unit  Weight  (lbs/ft3) ColorMaterial  Name 0None31150Mohr‐ Coulomb120Qtm  Static 0None05000Mohr‐ Coulomb135Tm Safety Factor 0.0 0.3 0.5 0.8 1.0 1.3 1.5 1.8 2.0 2.3 2.5 2.8 3.0 3.3 3.5 3.8 4.0 4.3 4.5 4.8 5.0 5.3 5.5 5.8 6.0+ 80 60 40 20 0 -40 -20 0 20 40 60 80 100 Scenario Wall/Static ConditionGroupXSA Company Geofirm/Stoney-Miller Consultants, Inc.Drawn By ZW Figure No.Figure D-1.3Date7/29/2020 Project Dawson Residence 2741 Ocean Boulevard, Corona del Mar, California SLIDEINTERPRET 9.008 1.01.0 400.00 lbs/ft2 200.00 lbs/ft2 200.00 lbs/ft2 0.00 lbs/ft2 300.00 lbs/ft2 1.01.0 0.4 RuWater  Surface Phi  (deg) Cohesion  (psf) Strength  Type Unit  Weight  (lbs/ft3) ColorMaterial  Name 0None30400Mohr‐ Coulomb120Qtm  Seismic 0None05000Mohr‐ Coulomb135Tm Safety Factor 0.0 0.3 0.5 0.8 1.0 1.3 1.5 1.8 2.0 2.3 2.5 2.8 3.0 3.3 3.5 3.8 4.0 4.3 4.5 4.8 5.0 5.3 5.5 5.8 6.0+ 12 0 10 0 80 60 40 20 0 -80 -60 -40 -20 0 20 40 60 80 100 120 Scenario Wall/Seismic ConditionGroupXSA Company Geofirm/Stoney-Miller Consultants, Inc.Drawn By ZW Figure No.Figure D-1.4Date7/29/2020 Project Dawson Residence 2741 Ocean Boulevard, Corona del Mar, California SLIDEINTERPRET 9.008 1.51.5 500.00 lbs/ft2 1.51.5 RuWater  Surface Phi  (deg) Cohesion  (psf) Strength  Type Unit  Weight  (lbs/ft3) ColorMaterial  Name 0None31150Mohr‐ Coulomb120Qtm  Static 0None05000Mohr‐ Coulomb135Tm 0None280Mohr‐ Coulomb115Qb Safety Factor 0.0 0.3 0.5 0.8 1.0 1.3 1.5 1.8 2.0 2.3 2.5 2.8 3.0 3.3 3.5 3.8 4.0 4.3 4.5 4.8 5.0 5.3 5.5 5.8 6.0+ 80 60 40 20 0 -20 0 20 40 60 80 100 120 140 Scenario Global/Static ConditionGroupXSB Company Geofirm/Stoney-Miller Consultants, Inc.Drawn By ZW Figure No.Figure D-2.1Date7/29/2020 Project Dawson Residence 2741 Ocean Boulevard, Corona del Mar, California SLIDEINTERPRET 9.008 1.81.8 500.00 lbs/ft2 1.81.8 0.15 RuWater  Surface Phi  (deg) Cohesion  (psf) Strength  Type Unit  Weight  (lbs/ft3) ColorMaterial  Name 0None30400Mohr‐ Coulomb120Qtm  Seismic 0None05000Mohr‐ Coulomb135Tm 0None280Mohr‐ Coulomb115Qb Safety Factor 0.0 0.3 0.5 0.8 1.0 1.3 1.5 1.8 2.0 2.3 2.5 2.8 3.0 3.3 3.5 3.8 4.0 4.3 4.5 4.8 5.0 5.3 5.5 5.8 6.0+ 80 60 40 20 0 0 20 40 60 80 100 120 Scenario Global/Seismic ConditionGroupXSB Company Geofirm/Stoney-Miller Consultants, Inc.Drawn By ZW Figure No.Figure D-2.2Date7/29/2020 Project Dawson Residence 2741 Ocean Boulevard, Corona del Mar, California SLIDEINTERPRET 9.008 3.93.9 500.00 lbs/ft2 3.93.9 RuWater  Surface Phi  (deg) Cohesion  (psf) Strength  Type Unit  Weight  (lbs/ft3) ColorMaterial  Name 0None31150Mohr‐ Coulomb120Qtm  Static 0None05000Mohr‐ Coulomb135Tm 0None280Mohr‐ Coulomb115Qb Safety Factor 0.0 0.3 0.5 0.8 1.0 1.3 1.5 1.8 2.0 2.3 2.5 2.8 3.0 3.3 3.5 3.8 4.0 4.3 4.5 4.8 5.0 5.3 5.5 5.8 6.0+ 60 40 20 0 -20 0 20 40 60 80 100 120 Scenario Wall/Static ConditionGroupXSB Company Geofirm/Stoney-Miller Consultants, Inc.Drawn By ZW Figure No.Figure D-2.3Date7/29/2020 Project Dawson Residence 2741 Ocean Boulevard, Corona del Mar, California SLIDEINTERPRET 9.008 2.72.7 500.00 lbs/ft2 2.72.7 0.4 RuWater  Surface Phi  (deg) Cohesion  (psf) Strength  Type Unit  Weight  (lbs/ft3) ColorMaterial  Name 0None30400Mohr‐ Coulomb120Qtm  Seismic 0None05000Mohr‐ Coulomb135Tm 0None280Mohr‐ Coulomb115Qb Safety Factor 0.0 0.3 0.5 0.8 1.0 1.3 1.5 1.8 2.0 2.3 2.5 2.8 3.0 3.3 3.5 3.8 4.0 4.3 4.5 4.8 5.0 5.3 5.5 5.8 6.0+ 60 40 20 0 -20 0 20 40 60 80 100 120 Scenario Wall/Seismic ConditionGroupXSB Company Geofirm/Stoney-Miller Consultants, Inc.Drawn By ZW Figure No.Figure D-2.4Date7/29/2020 Project Dawson Residence 2741 Ocean Boulevard, Corona del Mar, California SLIDEINTERPRET 9.008 1.01.0 600.00 lbs/ft2 0.00 lbs/ft2 340.00 lbs/ft2 1.01.0 RuWater  Surface Phi  (deg) Cohesion  (psf) Strength  Type Unit  Weight  (lbs/ft3) ColorMaterial  Name 0None31150Mohr‐ Coulomb120Qtm  Static 0None05000Mohr‐ Coulomb135Tm Safety Factor 0.0 0.3 0.5 0.8 1.0 1.3 1.5 1.8 2.0 2.3 2.5 2.8 3.0 3.3 3.5 3.8 4.0 4.3 4.5 4.8 5.0 5.3 5.5 5.8 6.0+ 80 60 40 20 0 -20 0 20 40 60 80 100 120 140 Scenario Wall/Static ConditionGroupXSC Company Geofirm/Stoney-Miller Consultants, Inc.Drawn By ZW Figure No.Figure D-3.1Date7/29/2020 Project Dawson Residence 2741 Ocean Boulevard, Corona del Mar, California SLIDEINTERPRET 9.008 1.01.0 600.00 lbs/ft2 0.00 lbs/ft2 340.00 lbs/ft2 1.01.0 0.4 RuWater  Surface Phi  (deg) Cohesion  (psf) Strength  Type Unit  Weight  (lbs/ft3) ColorMaterial  Name 0None30400Mohr‐ Coulomb120Qtm  Seismic 0None05000Mohr‐ Coulomb135Tm Safety Factor 0.0 0.3 0.5 0.8 1.0 1.3 1.5 1.8 2.0 2.3 2.5 2.8 3.0 3.3 3.5 3.8 4.0 4.3 4.5 4.8 5.0 5.3 5.5 5.8 6.0+ 15 0 10 0 50 0 -50 -25 0 25 50 75 100 125 150 175 200 225 Scenario Wall/Static ConditionGroupXSC Company Geofirm/Stoney-Miller Consultants, Inc.Drawn By ZW Figure No.Figure D-3.2Date7/29/2020 Project Dawson Residence 2741 Ocean Boulevard, Corona del Mar, California SLIDEINTERPRET 9.008 1.01.0 0.00 lbs/ft2 81.00 lbs/ft2 1.01.0 RuWater  Surface Phi  (deg) Cohesion  (psf) Strength  Type Unit  Weight  (lbs/ ft3) ColorMaterial  Name 0None31150Mohr‐ Coulomb120Qtm  Static 0None05000Mohr‐ Coulomb135Tm Safety Factor 0.0 0.3 0.5 0.8 1.0 1.3 1.5 1.8 2.0 2.3 2.5 2.8 3.0 3.3 3.5 3.8 4.0 4.3 4.5 4.8 5.0 5.3 5.5 5.8 6.0+ 60 40 20 0 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 Scenario Wall/Static ConditionGroupXSD Company Geofirm/Stoney-Miller Consultants, Inc.Drawn By ZW Figure No.Figure D-4.1Date7/30/2020 Project Dawson Residence 2741 Ocean Boulevard, Corona del Mar, California SLIDEINTERPRET 9.008 1.41.4 0.00 lbs/ft2 81.00 lbs/ft2 1.41.4 0.4 RuWater  Surface Phi  (deg) Cohesion  (psf) Strength  Type Unit Weight  (lbs/ft3)ColorMaterial  Name 0None30400Mohr‐ Coulomb120Qtm  Seismic 0None05000Mohr‐ Coulomb135Tm Safety Factor 0.0 0.3 0.5 0.8 1.0 1.3 1.5 1.8 2.0 2.3 2.5 2.8 3.0 3.3 3.5 3.8 4.0 4.3 4.5 4.8 5.0 5.3 5.5 5.8 6.0+ 60 40 20 0 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 Scenario Wall/Seismic ConditionGroupXSD Company Geofirm/Stoney-Miller Consultants, Inc.Drawn By ZW Figure No.Figure D-4.2Date7/30/2020 Project Dawson Residence 2741 Ocean Boulevard, Corona del Mar, California SLIDEINTERPRET 9.008 APPENDIX E STANDARD GRADING SPECIFICATIONS APPENDIX E STANDARD GRADING SPECIFICATIONS GENERAL These Guidelines present the usual and minimum requirements for grading operations observed and tested by Geofirm, or its designated representative. No deviation from these guidelines 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 geotechnical engineer or any person or persons employed by the licensed geotechnical engineer signing the soils report. If unsatisfactory soil-related conditions exist, the geotechnical 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 geotechnical engineer. SITE PREPARATION All brush, vegetation and other deleterious material such as rubbish shall be collected, piled and removed from the site prior to placing fill, leaving the site clear and free from objectionable material. Soil, alluvium, or rock materials determined by the geotechnical 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 geotechnical engineer. The surface shall then be plowed or scarified to a minimum depth of 6 inches until the surface is free from uneven features that would tend to prevent uniform compaction by the equipment used. After the area to receive fill has been cleared and scarified, it shall be diced or bladed by the contractor until it is uniform and free from large clods, brought to the proper moisture content, and compacted to minimum requirements. If the scarified zone is greater than 12 inches in depth, the excess shall be removed and placed in lifts restricted to 6 inches. Any underground structures such as cesspools, cisterns, mining shafts, tunnels, septic tanks, wells, pipelines, or others not located prior to grading are to be removed or treated in a manner prescribed by the geotechnical engineer. MATERIALS Materials for compacted fill shall consist of materials approved by the geotechnical engineer. These materials may be excavated from the cut area or imported from other approved sources, and soils from one or more sources may be blended. Fill soils shall be free from organic vegetable matter and other unsuitable substances. Normally, the material shall contain no rocks or hard lumps greater than 6 inches in size and shall contain at least 50 percent of material smaller than 1/4-inch in size. Materials greater than 4 inches in size shall be placed so that they are completely surrounded by compacted fines; no nesting of rocks shall be permitted. No material of a perishable, spongy, or otherwise of an unsuitable nature shall be used in the fill soils. Representative samples of materials to be utilized as compacted fill shall be analyzed in the laboratory by the geotechnical 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 geotechnical 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 (five layers). Compaction shall be accomplished by sheepsfoot rollers, vibratory rollers, multiple-wheel 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. GRADING OBSERVATIONS AND TESTING The geotechnical engineer shall observe and test the placement of fill during the grading process and will file a written report upon completion of grading stating his observations as to compliance with these specifications. One density test shall be required for each 2 vertical feet of fill placed, or one for each 1,000 cubic yards of fill, whichever requires the greater number of tests. Any cleanouts and processed ground to receive fill must be observed by the geotechnical 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 and tests of the completed grading, no further excavations and/or filling shall be performed without the approval of the geotechnical engineer, if it is to be subject to the recommendations of this report. APPENDIX F UTILITY TRENCH BACKFILL GUIDELINES APPENDIX F UTILITY TRENCH BACKFILL GUIDELINES The following guidelines pertinent to utility trench backfills have been adopted by the County of Orange, Environmental Management Agency Grading Section, effective March 31, 1986. The application of the guidelines is strictly enforced by the County reviewers and inspectors. 1. Each utility subcontractor (gas, electric, water, sewer, telephone, cable TV, irrigation, drainage, etc.) shall submit to the developer for dissemination to his consultants (civil engineer, geotechnical engineer, and utility contractor) a plot plan of 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 which includes a plot plan showing the location of all utility trenches which: A. Are located within the load influence zone of a structure (1:1 projection) B. Are located beneath any hardscape C. Are parallel and in close proximity to the top or toe of a slope and may adversely impact slope stability if improperly backfilled D. Are located on the face of a slope in a trench 18 or more inches in depth. Typically, trenches that are less than 18 inches in depth will not be within the load influence zone if located next to a structure, and will not have a significant effect on slope stability if constructed near the top or toe of a slope and need not be shown on the plot plan unless determined to be significant by the geotechnical engineer. This plot plan may be prepared by someone other than the geotechnical engineer, but must meet his approval. 4. Backfill compaction test locations must be shown on the plot plan described in No. 3 above, and a table of test data provided in the geotechnical report. 5. The geotechnical report (utility trench backfill) must state that all utility trenches within the subject lots have been backfilled in a manner suitable for the intended use. This includes the backfill of all trenches shown on the plot plan described in No. 3 and the backfill of those trenches which did not need to be plotted on this plan. UPDATED GEOTECHNICAL PLOT PLAN 2741 OCEAN BOULEVARD CORONA DEL MAR, CALIFORNIA 72681-00 DECEMBER 2022 1 JOB NO.:REPORT NO.:DATE:PLATE: 22-9231 SCALE: 1"=10' ? ? ? ? ? ? ? ?? C-2 C-1 Qsw Qsw Qtm Qtm Tm Tm TmQsw ? ? ?? ? ? ? ? ? ? ? ? ?? ? ? Qb/Af (?) D D' B B' C C' C-2 Tm BEDROCK - MONTEREY FORMATION, CIRCLED WHERE BURIED APPROXIMATE CORE LOCATION EXPLANATION Qb/Af (?)INFERRED BEACH AND FILL DEPOSITS Qtm MARINE TERRACE DEPOSITS, CIRCLED WHERE BURIED ?APPROXIMATE GEOLOGIC CONTACT, DOTTED WHERE BURIED, QUERIED WHERE UNCERTAIN Qsw SLOPEWASH ⅊ ⅊ ⅊ ⅊ ⅊ ⅊ 70 60 50 40 30 20 10 C C' 0 EL E V A T I O N ( F E E T , P E R P L A N ) 70 60 50 40 30 20 10 D D' 0 EL E V A T I O N ( F E E T , P E R P L A N ) 70 60 50 40 30 20 10 B B' 0 EL E V A T I O N ( F E E T , P E R P L A N ) TYPICAL BEDDING, APPARENT, CONVOLUTED TY P I C A L B E D D I N G , AP P A R E N T , C O N V O L U T E D TY P I C A L B E D D I N G , AP P A R E N T , C O N V O L U T E D UPDATED GEOTECHNICAL CROSS SECTIONS B-B', C-C' & D-D' 2741 OCEAN BOULEVARD CORONA DEL MAR, CALIFORNIA 72681-00 DECEMBER 2022 2 JOB NO.:REPORT NO.:DATE:PLATE: 22-9231 Tm Tm Qtm Qsw Qtm Qtm Tm Tm Tm Tm Qsw QbQb Qsw EXISTING GRADE EXISTING GRADE EXISTING GRADE C-2 C-2 (PROJECTED) MINIMUM 10' CAISSONS (TYP.)