Item 23 - First One -Year Extension for Site Plan Review No. 2020-03 and Variance No. 2020-06

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7.7.3 The maximum expected static settlement for the five -story residential structure supported on a conventional foundation system designed with a maximum bearing pressure of 5,000 psf and deriving support in the recommended bearing materials is estimated to be less than %2 inch and occur below the heaviest loaded structural element. Settlement of the foundation system is expected to occur on initial application of loading. Differential settlement is not expected to exceed'/a inch over a distance of 20 feet. 7.7.4 It is recommended that either a seismic separation or flexible connection be utilized where the apartment structures and parking structure may be attached. The design of the connection is at the discretion of the project structural engineer. Additional settlement analyses should be performed once the foundation loading configuration for the proposed structures is finalized to further evaluate the potential for differential settlement between the residential structure and parking structure. The utilization of a lesser bearing value, or increasing the thickness of engineered fill below the foundations, would further reduce the anticipated settlements and could be evaluated once the design becomes more finalized. 7.7.5 It is recommended that flexible utility connections be utilized for all rigid utilities to minimize or prevent damage to utilities from minor differential movements. 7.7.6 Once the design and foundation loading configurations for the proposed structures proceeds to a more finalized plan, the estimated settlements presented in this report should be reviewed and revised, if necessary. If the final foundation loading configurations are greater than the assumed loading conditions, the potential for settlement should be reevaluated by this office. 7.8 Miscellaneous Foundations 7.8.1 Foundations for small outlying structures, such as block walls up to 6 feet in height, planter walls or trash enclosures, which will not be structurally supported by the proposed building, may be supported on conventional foundations deriving support on a minimum of 12 inches of newly placed engineered fill which extends laterally at least 12 inches beyond the foundation area. Where excavation and compaction cannot be performed, such as adjacent to property lines, foundations may derive support in the undisturbed alluvial soils, and should be deepened as necessary to maintain a minimum 12-inch embedment into the recommended bearing materials. Geocon Project No. A9799-88-01 -19- June 7, 2022 7.8.2 If the soils exposed in the excavation bottom are loose, compaction of the soils will be required prior to placing steel or concrete. Compaction of the foundation excavation bottom is typically accomplished with a compaction wheel or mechanical whacker and must be observed and approved by a Geocon representative. Miscellaneous foundations may be designed for a bearing value of 1,500 psf, and should be a minimum of 12 inches in width, 18 inches in depth below the lowest adjacent grade and 12 inches into the recommended bearing material. The allowable bearing pressure may be increased by up to one-third for transient loads due to wind or seismic forces. 7.8.3 Foundation excavations should be observed and approved in writing by the Geotechnical Engineer (a representative of Geocon West, Inc.), prior to the placement of reinforcing steel and concrete to verify that the excavations and exposed soil conditions are consistent with those anticipated. 7.9 Lateral Design 7.9.1 Resistance to lateral loading may be provided by friction acting at the base of foundations, slabs and by passive earth pressure. An allowable coefficient of friction of 0.35 may be used with the dead load forces in the newly placed engineered fill or undisturbed alluvial soils. 7.9.2 Passive earth pressure for the sides of foundations and slabs poured against newly placed engineered fill or undisturbed alluvial soils may be computed as an equivalent fluid having a density of 230 pounds per cubic foot (pcf) with a maximum earth pressure of 2,300 psf. When combining passive and friction for lateral resistance, the passive component should be reduced by one-third. A one-third increase in the passive value may be used for wind or seismic loads. 7.10 Concrete Slabs -on -Grade 7.10.1 Concrete slabs -on -grade subject to vehicle loading should be designed in accordance with the recommendations in the Preliminary Pavement Recommendations section of this report (Section 7.11). 7.10.2 Subsequent to the recommended grading, concrete slabs -on -grade for structures, not subject to vehicle loading, should be a minimum of 4 inches thick and minimum slab reinforcement should consist of No. 3 steel reinforcing bars placed 18 inches on center in both horizontal directions. Steel reinforcing should be positioned vertically near the slab midpoint. Geocon Project No. A9799-88-01 -20- June 7, 2022 PHASE 2 STRUCTURAL FOOTING TO BE PLACED OVER /\/\/ >,/A;R 11401 / INITIAL CONCRETE POUR _-_-4-_-_-�-_-PHASE 1 STRUCTURAL CONCRETE IN jTA/ L p jITj SLOT CUTS j/ 7.6.5 If two-part foundation construction is used, the structural footing will be bounded laterally by artificial fill and, therefore, passive pressure along the sides of the foundations cannot be utilized. Resistance to lateral loads should be provided via structural connections to other portions of the structure. 7.6.6 Continuous footings may be designed for an allowable bearing capacity of 2,500 pounds per square foot (psf), and should be a minimum of 12 inches in width, 18 inches in depth below the lowest adjacent grade, and 12 inches into the recommended bearing material. 7.6.7 Isolated spread foundations may be designed for an allowable bearing capacity of 3,000 psf, and should be a minimum of 24 inches in width, 18 inches in depth below the lowest adjacent grade, and 12 inches into the recommended bearing material. 7.6.8 The allowable soil bearing pressure above may be increased by 250 psf and 500 psf for each additional foot of foundation width and depth, respectively, up to a maximum allowable soil bearing pressure of 5,000 psf. 7.6.9 The allowable bearing pressures may be increased by one-third for transient loads due to wind or seismic forces. Geocon Project No. A9799-88-01 - 17 - June 7, 2022 7.6.10 Continuous footings should be reinforced with a minimum of four No. 4 steel reinforcing bars, two placed near the top of the footing and two near the bottom. The reinforcement for isolated spread footings should be designed by the project structural engineer. 7.6.11 If depth increases are utilized for the exterior wall footings, this office should be provided a copy of the final construction plans so that the excavation recommendations presented herein could be properly reviewed and revised if necessary. 7.6.12 No special subgrade presaturation is required prior to placement of concrete. However, the slab and foundation subgrade should be sprinkled as necessary; to maintain a moist condition as would be expected in any concrete placement. 7.6.13 Foundation excavations should be observed and approved in writing by the Geotechnical Engineer (a representative of Geocon West, Inc.), prior to the placement of reinforcing steel and concrete to verify that the excavations and exposed soil conditions are consistent with those anticipated. If unanticipated soil conditions are encountered, foundation modifications may be required. 7.6.14 This office should be provided a copy of the final construction plans so that the excavation recommendations presented herein could be properly reviewed and revised if necessary. 7.7 Foundation Settlement 7.7.1 The maximum expected static settlement for the parking structures supported on a conventional foundation system designed with a maximum bearing pressure of 5,000 psf, and deriving support in the recommended bearing materials is estimated to be less than 1 inch and occur below the heaviest loaded structural element. Settlement of the foundation system is expected to occur on initial application of loading. Differential settlement is not expected to exceed %Z inch over a distance of 20 feet. 7.7.2 The maximum expected static settlement for the seven -story mixed -use structure supported on a conventional foundation system designed with a maximum bearing pressure of 5,000 psf and deriving support in the recommended bearing materials is estimated to be less than 1 %2 inches and occur below the heaviest loaded structural element. Settlement of the foundation system is expected to occur on initial application of loading. Differential settlement is not expected to exceed 3/4 inch over a distance of 20 feet. Geocon Project No. A9799-88-01 _18- June 7, 2022 7.4.9 Foundations for small outlying structures, such as block walls up to 6 feet high, planter walls or trash enclosures, which will not be tied to the proposed structure, may be supported on conventional foundations bearing on a minimum of 12 inches of newly placed engineered fill which extends laterally at least 12 inches beyond the foundation area. Where excavation and proper compaction cannot be performed, foundations may derive support directly in the undisturbed alluvial soils, and should be deepened as necessary to maintain a minimum 12-inch embedment into the recommended bearing materials. If the soils exposed in the excavation bottom are soft or loose, compaction of the soils will be required prior to placing steel or concrete. Compaction of the foundation excavation bottom is typically accomplished with a compaction wheel or mechanical whacker and must be observed and approved in writing by a Geocon representative. 7.4.10 All imported fill shall be observed, tested, and approved by Geocon West, Inc. prior to bringing soil to the site. Rocks larger than 6 inches in diameter shall not be used in the fill. Import soils used as structural fill should have an expansion index less than 20 and corrosivity properties that are equally or less detrimental to that of the existing onsite soils (see Figure 139). Import soils placed in the building area should be placed uniformly across the building pad or in a manner that is approved by the Geotechnical Engineer (a representative of Geocon). 7.4.11 Utility trenches should be properly backfilled in accordance with the following requirements. The pipe should be bedded with clean sands (Sand Equivalent greater than 30) to a depth of at least I foot over the pipe, and the bedding material must be inspected and approved in writing by the Geotechnical Engineer (a representative of Geocon). The use of gravel is not acceptable unless used in conjunction with filter fabric to prevent the gravel from having direct contact with soil. The remainder of the trench backfill may be derived from onsite soil or approved import soil, compacted as necessary, until the required compaction is obtained. The use of minimum 2-sack slurry as backfill is also acceptable. Prior to placing any bedding materials or pipes, the trench excavation bottom must be observed and approved in writing by the Geotechnical Engineer (a representative of Geocon). 7.4.12 All trench and foundation excavation bottoms must be observed and approved in writing by the Geotechnical Engineer (a representative of Geocon), prior to placing bedding sands, fill, steel, gravel, or concrete. 7.5 Shrinkage 7.5.1 Shrinkage results when a volume of material removed at one density is compacted to a higher density. A shrinkage factor of between 10 and 20 percent should be anticipated when excavating and compacting the upper 5 feet of existing earth materials on the site to an average relative compaction of 92 percent. Geocon Project No. A9799-88-01 -15- June 7, 2022 7.4.2 If import soils will be utilized in the building pads, the soils must be placed uniformly and at equal thickness at the direction of the Geotechnical Engineer (a representative of Geocon West, Inc.). Soils can be borrowed from non -building pad areas and later replaced with imported soils. 7.6 Foundation Design 7.6.1 Subsequent to the recommended grading, a conventional shallow spread foundation system may be utilized for support of the proposed structures provided foundations derive support in newly placed engineered fill and/or the competent alluvial soils found at and below a depth of 5 feet. It is the intent of the Geotechnical Engineer to allow building foundations to derive support in both engineered fill and competent alluvial soils for this project if conditions warrant such an occurrence. All foundation excavations must be observed and approved in writing by the Geotechnical Engineer (a representative of Geocon) prior to placing steel or concrete. Any exposed soft soils should be compacted to a dense state or penetrated by proposed foundations at the direction of the Geotechnical Engineer (a representative of Geocon West, Inc.). 7.6.2 Special excavation measures, such as slot cutting, will be required to construct foundations along the property line. Recommendations for slot cutting are provided in Section 7.18 of this report. 7.6.3 Foundations along the property line may be constructed in two phases using slot cutting to create temporary excavations and quickly restore the majority of the support. It is recommended that this project be mass graded prior to performing any foundation excavations along the property lines. 7.6.4 The first phase of foundation construction will be to excavate a temporary slot -cut excavation. The lower portion of the excavation, once approved by Geocon, can be backfilled with structural concrete up to the desired bottom of foundation depth. The project structural engineer should determine if the Phase 1 concrete pour requires any reinforcing and/or a key between the two pours. The excavation should be backfilled on the same day the excavation is opened. The second phase of the foundation construction will be to place the reinforced structural foundation on top of the previously placed Phase 1 concrete. The two-part foundation construction is illustrated below. Geocon Project No. A9799-88-01 - 16 - June 7, 2022 7.3.2 Laboratory tests were performed on representative samples of the site materials to measure the percentage of water-soluble sulfate content. Results from the laboratory water-soluble sulfate tests are presented in Appendix B (Figure 139) and indicate that the on -site materials possess sulfate exposure class of "SO" to concrete structures as defined by 2019 CBC Section 1904 and ACI 318-19 Chapter 19. 7.3.3 Geocon West, Inc. does not practice in the field of corrosion engineering and mitigation. If corrosion sensitive improvements are planned, it is recommended that a corrosion engineer be retained to evaluate corrosion test results and incorporate the necessary precautions to avoid premature corrosion of buried metal pipes and concrete structures in direct contact with the soils. 7.4 Grading 7.4.1 A preconstruction conference should be held at the site prior to the beginning of grading operations with the owner, contractor, civil engineer and soil engineer in attendance. Special soil handling requirements can be discussed at that time. 7.4.2 Earthwork should be observed, and compacted fill tested by representatives of Geocon West, Inc. The existing fill and alluvial soils encountered during exploration are suitable for reuse as engineered fill, provided any encountered oversize material (greater than 6 inches) and any encountered deleterious debris is removed. 7.4.3 Grading should commence with the removal of all existing vegetation and existing improvements from the area to be graded. Deleterious debris such as wood and root structures should be exported from the site and should not be mixed with the fill soils. Asphalt and concrete should not be mixed with the fill soils unless approved by the Geotechnical Engineer. All existing underground improvements planned for removal should be completely excavated and the resulting depressions properly backfilled in accordance with the procedures described herein. Once a clean excavation bottom has been established it must be observed and approved in writing by the Geotechnical Engineer (a representative of Geocon West, Inc.). Geocon Project No. A9799-88-01 -13- June 7, 2022 7.4.4 As a minimum, it is recommended that the upper 5 feet of existing earth materials within the proposed building footprint areas be excavated and properly compacted for foundation and slab support. Deeper excavations should be conducted as necessary to remove deeper artificial fill or soft alluvial soil at the direction of the Geotechnical Engineer (a representative of Geocon). The limits of existing fill and/or soft alluvial soils removal will be verified by the Geocon representative during site grading activities. The excavation should extend laterally a minimum distance of 3 feet beyond the building footprint area, including building appurtenances, or a distance equal to the depth of fill below the foundation, whichever is greater. Where the recommended lateral over -excavation cannot be performed, such as adjacent to a property line, foundations should be deepened as necessary to derive support in the undisturbed alluvial soils found at or below a depth of 5 feet. 7.4.5 All excavations must be observed and approved in writing by the Geotechnical Engineer (a representative of Geocon). Prior to placing any fill, the upper 12 inches of the excavation bottom must be scarified, moistened, and proof -rolled with heavy equipment in the presence of the Geotechnical Engineer (a representative of Geocon West, Inc.). Any exposed soft soils should be compacted to a dense state or penetrated by proposed foundations at the direction of the Geotechnical Engineer (a representative of Geocon West, Inc.). 7.4.6 All fill and backfill soils should be placed in horizontal loose layers approximately 6 to 8 inches thick, moisture conditioned to near optimum moisture content, and properly compacted to a minimum of 90 percent of the maximum dry density per ASTM D 1557 (latest edition). 7.4.7 It is anticipated that stable excavations for the recommended grading associated with the proposed structures can be achieved with sloping measures. However, if excavations in close proximity to an adjacent property line and/or structure are required, special excavation measures may be necessary in order to maintain lateral support of offsite improvements. Excavation recommendations are provided in the Temporary Excavations section of this report (see Section 7.17). 7.4.8. Where new paving is to be placed, it is recommended that all existing fill and soft alluvium be excavated and properly compacted for paving support. As a minimum, the upper 12 inches of soil should be scarified, moisture conditioned to near optimum moisture content, and compacted to at least 95 percent relative compaction, as determined by ASTM Test Method D 1557 (latest edition). Paving recommendations are provided in Preliminary Pavement Recommendations section of this report (see Sections 7.11 and 7.12). Geocon Project No. A9799-88-01 -14- June 7, 2022 Architecture + Planning 17911 Von Karman Ave. Suite 200 Irvine, CA 92614 ktgy.com 949.851.2133 KTGY Project No: 2017-0934 Project Contact: Debbie Holland Email: dholland@ktgy.com Principal: Wil Wong Project Designer: D. Schoolmeester Project Director: Debbie Holland Developer ED 0 A K INVESTi1iEN I'S 4199 CAMPUS DRIVE IRVINE, CA 92612 PHONE NO. (714) 342-2502 Sig TF r N C) Q U Q Z Q Q Z Q U) LU LU U) F_ NT L li Ln Ln 06 T_ Nt m No. Date Description H 75 00 D U) U w 2 U Z Q J It is the clients responsibility prior to or during construction to notify the architect in writing of any perceived errors or omissions in the plans and specifications of which a contractor thoroughly knowledgeable with the building codes and methods of construction should reasonably be aware. Written instructions addressing such perceived errors or omissions shall be received from the architect prior to the client or clients subcontractors proceeding with the work. The client will be responsible for any defects in construction if these procedures are not followed. v, S�D ARcj,11 ILL N No. C29795 0 RENEWAL DATE AUGUST 31, 2023 qTF OF 0 C�� A License Stamp o GEOTECHNICAL REPORT COPYRIGHT (c, AO-82