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7.1.6 Where miscellaneous subterranean improvements are planned Elevator Pits the structures <br />P p ( ), <br />may be supported on a conventional foundation system deriving support in the undisturbed <br />alluvial soils found at and below a depth of 5 feet. If necessary, these miscellaneous <br />improvements may derive support in a combination of newly placed engineered fill. and <br />competent alluvium found at and below a depth of 5 feet. It is the intent of the Geotechnical <br />Engineer to allow miscellaneous subterranean structures to derive support in both engineered <br />fill and alluvium if project conditions warrant such an occurrence. Recommendations for <br />elevator pit design are provided in Section 7.15. <br />7.1.7 It is anticipated that stable excavations for the recommended grading associated with the <br />proposed structures can be achieved with sloping measures. However, if excavations in close <br />proximity to an adjacent property line and/or structure are required, special excavation <br />measures may be necessary in order to maintain lateral support of offsite improvements. <br />Excavation recommendations are provided in the Temporary Excavations section of this report <br />(Section 7.17). <br />7.1.8 Foundations for small outlying structures, such as block walls up to 6 feet high, planter walls <br />or trash enclosures, which will not be tied to the proposed structure, may be supported on <br />conventional foundations bearing on a minimum of 12 inches of newly placed engineered fill <br />which extends laterally at least 12 inches beyond the foundation area. Where excavation and <br />proper compaction cannot be performed, foundations may derive support directly in the <br />undisturbed alluvial soils, and should be deepened as necessary to maintain a minimum <br />12-inch embedment into the recommended bearing materials. If the soils exposed in the <br />excavation bottom are soft or loose, compaction of the soils will be required prior to placing <br />steel or concrete. Compaction of the foundation excavation bottom is typically accomplished <br />with a compaction wheel or mechanical whacker and must be observed and approved in <br />writing by a Geocon representative. <br />7.1.9 Where new paving is to be placed, it is recommended that all existing fill soils and soft alluvial <br />soils be excavated and properly compacted for paving support. The client should be aware that <br />excavation and compaction of all existing fill in the area of new paving is not required, <br />however, paving constructed over existing uncertified fill or unsuitable soils may experience <br />increased settlement and/or cracking, and may therefore have a shorter design life and <br />increased maintenance costs. As a minimum, the upper 12 inches of soil should be scarified <br />and properly compacted. Paving recommendations are provided in the Preliminary Pavement <br />Recommendations section of this report (see Sections 7.11 and 7.12). <br />7.1.10 Based on the results of percolation testing performed at the site, a stormwater infiltration <br />system is considered feasible for this project. Recommendations for infiltration are provided <br />in the Stormwater Infiltration section of this report (see Section 7.19). <br />Geocon Project No. A9799-88-01 <br />-11- <br />June 7, 2022 <br />7.1.11 Once the design and foundation loading configuration for the proposed structure proceeds to <br />a more finalized plan, the recommendations within this report should be reviewed and revised, <br />if necessary. Based on the final foundation loading configurations, the potential for settlement <br />should be reevaluated by this office. <br />7.1.12 Any changes in the design, location or elevation of improvements, as outlined in this report, <br />should be reviewed by this office. Geocon should be contacted to determine the necessity for <br />review and possible revision of this report. <br />7.2 Soil and Excavation Characteristics <br />7.2.1 The in -situ soils can be excavated with moderate effort using conventional excavation <br />equipment. Caving should be anticipated in unshored excavations, especially where granular <br />soils are encountered. <br />7.2.2 It is the responsibility of the contractor to ensure that all excavations and trenches are properly <br />shored and maintained in accordance with applicable OSHA rules and regulations to maintain <br />safety and maintain the stability of adjacent existing improvements. <br />7.2.3 All onsite excavations must be conducted in such a manner that potential surcharges from <br />existing structures, construction equipment, and vehicle loads are resisted. The surcharge area <br />may be defined by a 1:1 projection down and away from the bottom of an existing foundation <br />or vehicle load. Penetrations below this 1:1 projection will require special excavation measures <br />such as sloping and shoring. Excavation recommendations are provided in the Temporary <br />Excavations section of this report (see Section 7.17). <br />7.2.4 The upper 5 feet of existing site soils encountered during this investigation are considered to <br />have a "very low" expansive potential (EI =1); and the soils are classified as "non -expansive" <br />based on the 2019 California Building Code (CBC) Section 1803.5.3. The recommendations <br />in this report assume that foundations and slabs will derive support in these materials. <br />7.3 Minimum Resistivity, pH, and Water -Soluble Sulfate <br />7.3.1 Potential of Hydrogen (pH) and resistivity testing as well as chloride content testing were <br />performed on representative samples of soil to generally evaluate the corrosion potential to <br />surface utilities. The tests were performed in accordance with California Test Method Nos. 643 <br />and 422 and indicate that the soils are considered "corrosive" with respect to corrosion of <br />buried ferrous metals on site. The results are presented in Appendix B (Figure B9) and should <br />be considered for design of underground structures. <br />Geocon Project No. A9799-88-01 -12- June 7, 2022 <br />6.8 Oil Fields & Methane Potential <br />Based on a review of the California Geologic Energy Management Division (Ca1GEM, 2022), the site is <br />not located near the boundary of an oil field and no oil wells are located in the immediate vicinity of the <br />site. Due to the voluntarynature of record reporting b the oil well drilling companies, wells may be <br />p g Y g p Y <br />improperly located or not shown on the well location map. Undocumented wells could be encountered <br />during construction. Any wells encountered will need to be properly abandoned in accordance with the <br />current requirements of the Ca1GEM. <br />Since the site is not located within the boundaries of a known oil field, the potential for the presence of <br />methane gas at the site is considered low. However, should it be determined that a methane study is <br />required for the proposed development it is recommended that a qualified methane consultant be retained <br />to perform the study and provide mitigation measures as necessary. <br />6.9 Subsidence <br />Subsidence occurs when a large portion of land is displaced vertically, usually due to the withdrawal of <br />groundwater, oil, or natural gas. Soils that are particularly subject to subsidence include those with high <br />silt or clay content. The site is not located within an area of known ground subsidence. No large-scale <br />extraction of groundwater, gas, oil, or geothermal energy is occurring or planned at the site. There <br />appears to be little or no potential for ground subsidence due to withdrawal of fluids or gases at the site. <br />Geocon Project No. A9799-88-01 <br />7.1 General <br />-9- <br />7. CONCLUSIONS AND RECOMMENDATIONS <br />June 7, 2022 <br />7.1.1 It is our opinion that neither soil nor geologic conditions were encountered during the <br />investigation that would preclude the construction of the proposed development provided the <br />recommendations presented herein are followed and implemented during design and <br />construction. <br />7.1.2 Up to 5 feet of existing artificial fill was encountered during the site investigation. <br />The existing fill encountered is believed to be the result of past grading and construction <br />activities at the site. Deeper fill may exist in other areas of the site that were not directly <br />explored. It is our opinion that the existing fill, in its present condition, is not suitable for direct <br />support of proposed foundations or slabs. The existing fill and site soils are suitable for re -use <br />as engineered fill provided the recommendations in the Grading section of this report are <br />followed (see Section 7.4). <br />7.1.3 Based on these considerations, it is recommended that the upper 5 feet of existing earth <br />materials within the buildingfootprint areas be excavated and properly compacted for <br />tP P P Y p <br />foundation and slab support. Deeper excavations should be conducted as needed to remove <br />any encountered fill or soft soils as necessary at the direction of the Geotechnical Engineer (a <br />representative of Geocon). The limits of existing fill and/or soft soil removal will be verified <br />by the Geocon representative during site grading activities. The excavation should extend <br />laterally a minimum distance of three feet beyond the building footprint areas, including <br />building appurtenances, or a distance equal to the depth of fill below the foundation, whichever <br />is greater. Where the recommended lateral over -excavation cannot be performed, such as <br />adjacent to a property line, foundations should be deepened as necessary to derive support in <br />the undisturbed alluvial soils found at and below a depth of 5 feet. Recommendations for <br />earthwork are provided in the Grading section of this report (see Section 7.4). <br />7.1.4 All excavations must be observed and approved in writing by the Geotechnical Engineer (a <br />representative of Geocon). Prior to placing any fill, the upper 12 inches of the excavation <br />bottom must be scarified, moistened, and proof -rolled with heavy equipment in the presence <br />of the Geotechnical Engineer (a representative of Geocon West, Inc.). <br />7.1.5 Subsequent to the recommended grading, the proposed structures may be supported on a <br />conventional shallow spread foundation system deriving support in newly placed engineered <br />fill and/or the competent alluvial soils found at and below a depth of 5 feet. It is the intent of <br />the Geotechnical Engineer to allow building foundations to derive support in both engineered <br />fill and competent alluvial soils for this project if conditions warrant such an occurrence. Any <br />exposed soft soils should be compacted to a dense state or penetrated by proposed foundations <br />at the direction of the Geotechnical Engineer (a representative of Geocon West, Inc.). <br />Geocon Project No. A9799-88-01 _10- June 7, 2022 <br />The Maximum Considered Earthquake Ground Motion (MCE) is the level of ground motion that has a <br />2 percent chance of exceedance in 50 years, with a statistical return period of 2,475 years. According to <br />the 2019 California Building Code and NEHRP-2015, the MCE is to be utilized for the evaluation of <br />liquefaction, lateral spreading, seismic settlements, and it is our understanding that the intent of the <br />Building code is to maintain "Life Safety" during a MCE event. The Design Earthquake Ground Motion <br />(DE) is the level of ground motion that has a 10 percent chance of exceedance in 50 years, with a <br />statistical return period of 475 years. <br />Deaggregation of the MCE peak ground acceleration was performed using the USGS online Unified <br />Hazard Tool, 2014 Conterminous U.S. Dynamic edition (v4.2.0). The result of the deaggregation analysis <br />indicates that the predominant earthquake contributing to the MCE peak ground acceleration is <br />characterized as a 6.67 magnitude event occurring at a hypocentral distance of 15.03 kilometers from the <br />site. <br />Deaggregation was also performed for the Design Earthquake (DE) peak ground acceleration, and the <br />result of the analysis indicates that the predominant earthquake contributing to the DE peak ground <br />acceleration is characterized as a 6.61 magnitude occurring at a hypocentral distance of 21.16 kilometers <br />from the site. <br />Conformance to the criteria in the above tables for seismic design does not constitute any kind of <br />guarantee or assurance that significant structural damage or ground failure will not occur if a large <br />earthquake occurs. The primary goal of seismic design is to protect life, not to avoid all damage, since <br />such design may be economically prohibitive. <br />6.4 Liquefaction Potential <br />Liquefaction is a phenomenon in which loose, saturated, relatively cohesionless soil deposits lose shear <br />strength during strong ground motions. Primary factors controlling liquefaction include intensity and <br />duration of ground motion, gradation characteristics of the subsurface soils, in -situ stress conditions, and <br />the depth to groundwater. Liquefaction is typified by a loss of shear strength in the liquefied layers due <br />to rapid increases in pore water pressure generated by earthquake accelerations. <br />The current standard of practice, as outlined in the "Recommended Procedures for Implementation of <br />DMG Special Publication 117, Guidelines for Analyzing and Mitigating Liquefaction in California" and <br />"Special Publication 117A, Guidelines for Evaluating and Mitigating Seismic Hazards in California" <br />requires liquefaction analysis to a depth of 50 feet below the lowest portion of the proposed structure. <br />Liquefaction typically occurs in areas where the soils below the water table are composed of poorly <br />consolidated, fine to medium -grained, primarily sandy soil. In addition to the requisite soil conditions, <br />the ground acceleration and duration of the earthquake must also be of a sufficient level to induce <br />liquefaction. <br />Geocon Project No. A9799-88-01 -7- June 7, 2022 <br />A review of the State of California Seismic Hazard Zone Map for the Tustin Quadrangle (CGS, 2001) <br />indicates that the site is not located in an area designated as "liquefiable". A review of the Safety Element <br />of the General Plan for the City of Santa Ana indicates that the site is located in an area designated as <br />having the `Potential for Liquefaction' (City of Santa Ana, 2010). However, as stated previously, the <br />historic high groundwater level is reported to be in excess of 40 feet below the existing ground surface. <br />Based on these considerations, it is our opinion that the potential for liquefaction at the site is low. <br />6.5 Slope Stability <br />The topography at the site is relatively level and the site is not within an area identified as having a <br />potential for slope stability hazards (City of Santa Ana, 2010) or seismic slope instability hazards <br />(CDMG, 2001). No landslides have been identified at the site or in close proximity to the site. Also, the <br />site is not in the path of any known or potential landslides. Therefore, the potential for slope stability <br />hazards to adversely affect the proposed development is considered low. <br />6.6 Earthquake -Induced Flooding <br />Earthquake -induced flooding is inundation caused by failure of dams or other water -retaining structures <br />due to earthquakes. A review of the Safety Element of the Orange County General Plan (2004) and the <br />City of Santa Ana Seismic Safety Element (2010) indicates that the site is not located within the <br />inundation boundaries of upgradient dams, rivers, creeks, or reservoirs. The probability of earthquake - <br />induced flooding is considered very low. <br />6.7 Tsunamis, Seiches and Flooding <br />The site is not located within a coastal area. Therefore, tsunamis, seismic sea waves, are not considered <br />a significant hazard at the site. <br />Seiches are large waves generated in enclosed bodies of water in response to ground shaking. No major <br />water -retaining structures are located immediately up gradient from the project site. Flooding from a <br />seismically -induced seiche is considered unlikely. <br />The site is in located within an area of minimal flooding potential (Zone X) as defined by the Federal <br />Emergency Management Agency (FEMA, 2022). <br />Geocon Project No. A9799-88-01 - 8 - June 7, 2022 <br />6.2 Seismicity <br />As with all of Southern California, the site has experienced historic earthquakes from various regional <br />faults. The seismicity of the region surrounding the site was formulated based on research of an electronic <br />database of earthquake data. The epicenters of recorded earthquakes with magnitudes equal to or greater <br />than 5.0 in the site vicinity are depicted on Figure 4, Regional Seismicity Map. A partial list of moderate <br />to major magnitude earthquakes that have occurred in the Southern California area within the last <br />100 years is included in the following table. <br />LIST OF HISTORIC EARTHQUAKES <br />Earthquake <br />(Oldest to Youngest) <br />Date of Earthquake <br />Magnitude <br />Distance to <br />Epicenter <br />(Miles) <br />Direction <br />to <br />Epicenter <br />Near Redlands <br />July 23, 1923 <br />6.3 <br />39 <br />ENE <br />Long Beach <br />March 10, 1933 <br />6.4 <br />11 <br />SW <br />Tehachapi <br />July 21, 1952 <br />7.5 <br />108 <br />NW <br />San Fernando <br />February 9, 1971 <br />6.6 <br />55 <br />NW <br />Whittier Narrows <br />October 1, 1987 <br />5.9 <br />25 <br />NW <br />Sierra Madre <br />June 28, 1991 <br />5.8 <br />36 <br />NNW <br />Landers <br />June 28, 1992 <br />7.3 <br />87 <br />ENE <br />Big Bear <br />June 28, 1992 <br />6.4 <br />67 <br />ENE <br />Northridge <br />January 17, 1994 <br />6.7 <br />50 <br />NW <br />Hector Mine <br />October 16, 1999 <br />7.1 <br />1.08 <br />ENE <br />Rid ecrest <br />July 5, 2019 <br />7.1 <br />140 <br />N <br />The site could be subjected to strong ground shaking in the event of an earthquake. However, this hazard <br />is common in Southern California and the effects of ground shaking can be mitigated if the proposed <br />structures are designed and constructed in conformance with current building codes and engineering <br />practices. <br />6.3 Seismic Design Criteria <br />The following table summarizes the site -specific design criteria obtained from the 2019 California <br />Building Code (CBC; Based on the 2018 International Building Code [IBC] and ASCE 7-16), Chapter <br />16 Structural Design, Section 1.613 Earthquake Loads. The data was calculated using the online <br />application Seismic Design Maps, provided by OSHPD. The short spectral response uses a period of <br />0.2 second. We evaluated the Site Class based on the discussion in Section 1613.2.2 of the 2019 CBC <br />and Table 20.3-1 of ASCE 7-16. The values presented below are for the risk -targeted maximum <br />considered earthquake (MCER). <br />Geocon Project No. A9799-88-01 - 5 - <br />2019 CBC SEISMIC DESIGN PARAMETERS <br />June 7, 2022 <br />Parameter <br />Value <br />2019 CBC Reference <br />Site Class <br />D <br />Section 1613.2.2 <br />MCER Ground Motion Spectral Response <br />1.29g <br />Figure 1613.2.1(1) <br />Acceleration — Class B (short), Ss <br />MCER Ground Motion Spectral Response <br />0.46g <br />Figure 1613.2.1(2) <br />Acceleration — Class B (1 sec), SI <br />Site Coefficient, FA <br />I <br />Table 1613.2.3(1) <br />Site Coefficient, Fv <br />1.,,;4* <br />Table 1613.2.3(2) <br />Site Class Modified MCER Spectral Response <br />1.29g <br />Section 1613.2.3 (Eqn 16-36) <br />Acceleration (short), SMs <br />Site Class Modified MCER Spectral Response <br />0.846g* <br />Section 1613.2.3 (Eqn 16-37) <br />Acceleration — (1 sec), SMI <br />5% Damped Design <br />Spectral Response Acceleration (short), SDs <br />0.86g <br />Section 1613.2.4 (Eqn 16-38) <br />5% Damped Design <br />Spectral Response Acceleration (1 sec), SDI <br />0.564g* <br />Section 1613.2.4 (Eqn 16-39) <br />Note: <br />*Per Section 11.4.8 of ASCE/SEI 7-16, a ground motion hazard analysis shall be performed for <br />projects for Site Class "E" sites with Ss greater than or equal to 1.Og and for Site Class "D" and <br />"E" sites with S 1 greater than 0.2g. Section 11.4.8 also provides exceptions which indicates that <br />the ground motion hazard analysis may be waived provided the exceptions are followed. Using <br />the code based values presented in the table above, in lieu of a performing a ground motion <br />hazard analysis, requires the exceptions outlined in ASCE 7-16 Section 11.4.8 be followed. <br />The table below presents the mapped maximum considered geometric mean (MCEG) seismic design <br />parameters for projects located in Seismic Design Categories of D through F in accordance with ASCE <br />7-16. <br />ASCE 7-16 PEAK GROUND ACCELERATION <br />Parameter <br />Value <br />ASCE 7-16 Reference <br />Mapped MCEG Peak Ground Acceleration, <br />0.543g <br />Figure 22-9 <br />PGA <br />Site Coefficient, FPGA <br />1.1 <br />Table 11.8-1 <br />Site Class Modified MCEG Peak Ground <br />0.598g <br />Section 11.8.3 (Eqn 11.8-1) <br />Acceleration, PGAM <br />Geocon Project No. A9799-88-01 - 6 - June 7, 2022 <br />• <br />Architecture + Planning <br />17911 Von Karman Ave. <br />Suite 200 <br />Irvine, CA 92614 <br />ktgy.com <br />949.851.2133 <br />KTGY Project No: 2017-0934 <br />Project Contact: Debbie Holland <br />Email: dholland@ktgy.com <br />Principal: Wil Wong <br />Project Designer: D. Schoolmeester <br />Project Director: Debbie Holland <br />Developer <br />ED7 OAK <br />INVES'I'NiEN I'S <br />4199 CAMPUS DRIVE <br />IRVINE, CA 92612 <br />PHONE NO. (714) 342-2502 <br />1 <br />TF <br />r <br />N <br />M <br />Q <br />U <br />Q <br />Z <br />Q <br />Q <br />Z <br />Q <br />U) <br />W <br />w <br />U) <br />w <br />LO <br />V_ <br />L0 <br />06 <br />LO <br />No. Date Description H <br />m <br />U) <br />U <br />Lu <br />U <br />Z <br />Q <br />J <br />It is the clients responsibility prior to or during construction to notify the architect in writing <br />n <br />of any perceived errors or omissions in the plans and specifications of which a contractor <br />thoroughly knowledgeable with the building codes and methods of construction should <br />reasonably be aware. Written instructions addressing such perceived errors or omissions <br />shall be received from the architect prior to the client or clients subcontractors proceeding <br />jr <br />with the work. The client will be responsible for any defects in construction if these <br />procedures are not followed. <br />v J <br />0. <br />SED ARC,S,,T <br />ILL <br />�0 �� <br />N <br />(N <br />* No. C29795 * <br />C) <br />RENEWAL DATE <br />AUGUST 31, 2023 <br />of <br />C A�_ <br />License Stamp <br />o <br />GEOTECHNICAL <br />REPORT <br />COPYRIGHT (c <br />AO-81 <br />