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

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7.15.3 If retainingwall drainage is to be provided, the drainage system should be designed in g p g Y � accordance with the Retaining Wall Drainage section of this report (see Section 7.14). 7.15.4 It is suggested that the elevator pit walls and slab be waterproofed to prevent excessive moisture inside of the elevator pit. Waterproofing design and installation is not the responsibility of the geotechnical engineer. 7.16 Elevator Piston 7.16.1 If a plunger -type elevator piston is installed for this project, a deep drilled excavation will be required. It is important to verify that the drilled excavation is not situated immediately adjacent to a foundation, or the drilled excavation could compromise the existing foundation, especially if the drilling is performed subsequent to the foundation construction. 7.16.2 Casing may be required if caving is experienced in the drilled excavation. The contractor should be prepared to use casing and should have it readily available at the commencement of drilling activities. Continuous observation of the drilling and installation of the elevator piston by the Geotechnical Engineer (a representative of Geocon West, Inc.) is required. 7.16.3 The annular space between the piston casing and drilled excavation wall should be filled with a minimum of 1 %2-sack slurry pumped from the bottom up. As an alternative, pea gravel may be utilized. The use of soil to backfill the annular space is not acceptable. 7.17 Temporary Excavations 7.17.1 Excavations up to 5 feet in height may be required during grading and construction operations. The excavations are expected to expose artificial fill and alluvial soils, which are suitable for vertical excavations up to 5 feet in height where loose soils or caving sands are not present, and where not surcharged by adjacent traffic or structures. 7.17.2 Vertical excavations greater than 5 feet or where surcharged by existing structures will require sloping or shoring measures in order to provide a stable excavation. Where sufficient space is available, temporary unsurcharged embankments could be sloped back at a uniform 1:1 slope gradient or flatter up to a maximum height of 10 feet. A uniform slope does not have a vertical portion. 7.17.3 If excavations in close proximity to an adjacent property line and/or structure are required, special excavation measures such as slot -cutting or shoring may be necessary in order to maintain lateral support of offsite improvements. Recommendations for slot cutting are provided in Section 7.18 of this report. Geocon Project No. A9799-88-01 -27- June 7, 2022 7.17.4 Where temporary construction slopes are utilized, the top of the slope should be barricaded to prevent vehicles and storage loads at the top of the slope within a horizontal distance equal to the height of the slope. If the temporary construction slopes are to be maintained during the rainy season, berms are suggested along the tops of the slopes where necessary to prevent runoff water from entering the excavation and eroding the slope faces. Geocon personnel should inspect the soils exposed in the cut slopes during excavation so that modifications of the slopes can be made if variations in the soil conditions occur. All excavations should be stabilized within 30 days of initial excavation. 7.18 Slot Cutting 7.18.1 The slot -cutting employs method s the earth as a buttress and allows the earth excavation to p Y proceed in phases. Where slot -cutting is used for foundation construction, the proposed construction techniques should be discussed with the structural engineer so that appropriate modifications can be made to the foundation design, such as additional reinforcing or details for doweling. 7.18.2 It is recommended that the initial temporary excavation along the property line be sloped back at a uniform 1:1 (H:V) slope gradient or flatter for excavation of the existing soils to the necessary depth. The temporary excavation should not extend below the surcharge area of any adjacent foundations. The surcharge area may be defined by a 1:1 projection down and away from the bottom of an existing foundation. The temporary slope may then be excavated using the slot -cutting (see illustration below). Geocon Project No. A9799-88-01 - 28 - June 7, 2022 7.12.6 The performance of pavement is highly dependent on providingpositive surface drainage away from the edge of the pavement. Ponding of water on or adjacent to the pavement will likely result in pavement distress and subgrade failure. Drainage from landscaped areas should be directed to controlled drainage structures. Landscape areas adjacent to the edge of asphalt pavements are not recommended due to the potential for surface or irrigation water to infiltrate the underlying permeable aggregate base and cause distress. Where such a condition cannot be avoided, consideration should be given to incorporating measures that will significantly reduce the potential for subsurface water migration into the aggregate base. If planter islands are planned, the perimeter curb should extend at least 6 inches below the level of the base materials. 7.13 Retaining Wall Design 7.13.1 The recommendations presented below are generally applicable to the design of rigid concrete or masonry retaining walls having a maximum height of 5 feet. In the event that walls significantly higher than 5 feet are planned, Geocon should be contacted for additional recommendations. 7.13.2 Retaining wall foundations may be designed in accordance with the recommendations provided in the Foundation Design section of this report (see Section 7.6). 7.13.3 Retaining walls with a level backfill surface that are not restrained at the top should be designed utilizing a triangular distribution of pressure (active pressure) of 30 pcf. 7.13.4 Restrained walls are those that are not allowed to rotate more than 0.001H (where H equals the height of the retaining portion of the wall in feet) at the top of the wall. Where walls are restrained from movement at the top, walls may be designed utilizing a triangular distribution of pressure (at -rest pressure) of 65 pcf. 7.13.5 The wall pressures provided above assume that the proposed retaining walls will support relatively undisturbed alluvial soils or engineered fill derived from onsite soils. If import soil will be used to backfill proposed retaining walls, revised earth pressures may be required to account for the geotechnical properties of the import soil used as engineered fill. This should be evaluated once the use of import soil is established. All imported fill shall be observed, tested, and approved by Geocon West, Inc. prior to bringing soil to the site. 7.13.6 The wall pressures provided above assume that the retaining wall will be properly drained preventing the buildup of hydrostatic pressure. If retaining wall drainage is not implemented, the equivalent fluid pressure to be used in design of undrained walls is 95 pcf. The value includes hydrostatic pressures plus buoyant lateral earth pressures. Geocon Project No. A9799-88-01 -25- June 7, 2022 7.13.7 Additional active pressure should be added for a surcharge condition due to sloping ground, vehicular traffic or adjacent structures and should be designed for each condition as the project progresses. 7.14 Retaining Wall Drainage 7.14.1 Retaining walls not designed for hydrostatic pressures should be provided with a drainage system extended at least two-thirds the height of the wall. At the base of the drain system, a subdrain covered with a minimum of 12 inches of gravel should be installed, and a compacted fill blanket or other seal placed at the surface (see Figure 5). The clean bottom and subdrain pipe, behind a retaining wall, should be observed by the Geotechnical Engineer (a representative of Geocon), prior to placement of gravel or compacting backfill. 7.14.2 As an alternative, a plastic drainage composite such as Miradrain or equivalent may be installed in continuous, 4-foot-wide columns along the entire back face of the wall, at 8 feet on center. The top of these drainage composite columns should terminate approximately 18 inches below the ground surface, where either bardscape or a minimum of 18 inches of relatively cohesive material should be placed as a cap (see Figure 6). 7.14.3 Subdrainage pipes at the base of the retaining wall drainage system should outlet to an acceptable location via controlled drainage structures. Drainage should not be allowed to flow uncontrolled over descending slopes. 7.14.4 Moisture affecting below grade walls is one of the most common post -construction complaints. Poorly applied or omitted waterproofing can lead to efflorescence or standing water. Particular care should be taken in the design and installation of waterproofing to avoid moisture problems, or actual water seepage into the structure through any normal shrinkage cracks which may develop in the concrete walls, floor slab, foundations and/or construction joints. The design and inspection of the waterproofing is not the responsibility of the geotechnical engineer. A waterproofing consultant should be retained in order to recommend a product or method, which would provide protection to subterranean walls, floor slabs and foundations. 7.15 Elevator Pit Design 7.15.1 The elevator pit slab and retaining wall should be designed by the project structural engineer. Elevator pit walls may be designed in accordance with the recommendations in the Foundation Design and Retaining Wall Design sections of this report (see Sections 7.6 and 7.13). 7.15.2 Additional active pressure should be added for a surcharge condition due to sloping ground, vehicular traffic or adjacent foundations and should be designed for each condition as the project progresses. Geocon Project No. A9799-88-01 - 26 - June 7, 2022 7.11.4 Asphalt concrete should conform to Section 203-6 of the "Standard Specifications for Public Works Construction " (Green Book). Class 2 aggregate base materials should conform to Section 26-1.02A of the "Standard Specifications of the State of California, Department of Transportation " (Caltrans). The use of Crushed Miscellaneous Base (CMB) in lieu of Class 2 aggregate base is acceptable. Crushed Miscellaneous Base should conform to Section 200-2.4 of the "Standard Specifications for Public Works Construction " (Green Book). 7.11.5 Unless specifically designed and evaluated by the project structural engineer, where exterior concrete paving will be utilized for support of vehicles, it is recommended that the concrete be a minimum of 6 inches of concrete reinforced with No. 3 steel reinforcing bars placed 18 inches on center in both horizontal directions. Concrete paving supporting vehicular traffic should be underlain by a minimum of 4 inches of aggregate base and a properly compacted subgrade. The subgrade and base material should be compacted to 95 percent relative compaction, as determined by ASTM Test Method D 1557 (latest edition). 7.11.6 The performance of pavements is highly dependent upon providing positive surface drainage away from the edge of pavements. Ponding of water on or adjacent to the pavement will likely result in saturation of the subgrade materials and subsequent cracking, subsidence and pavement distress. If planters are planned adjacent to paving, it is recommended that the perimeter curb be extended at least 12 inches below the bottom of the aggregate base to minimize the introduction of water beneath the paving. 7.12 Vehicular Rated Concrete Paver Recommendations 7.12.1 The following recommendations are based on an assumed R-Value of 20. Once site grading activities are complete and prior to placing pavement, an R-Value should be obtained by laboratory testing to confirm the properties of the soils serving as paving subgrade. 7.12.2 We calculated the paver sections in general conformance with the Caltrans Method ofFlexible Pavement Design (Highway Design Manual, Section 608.4) using an estimated Traffic Indices (TI). The project civil engineer and owner should review the pavement designations to determine appropriate locations for pavement thickness. Based on the Interlocking Concrete Pavement Institute (ICPI), the pavers should possess a minimum thickness of 3f/8 inches overlying 1 to 1'/2 inch of sand. In addition, the pavers should be installed in a pattern acceptable for vehicular traffic. It is anticipated that base materials will be used for the paver underlayment. The pavers are for decorative purposes and will not be installed for stormwater management. The table below presents the recommended concrete -unit paver sections. Geocon Project No. A9799-88-01 -23- RECOMMENDED CONCRETE UNIT PAVER SECTIONS June 7, 2022 Equivalent Estimated Traffic Paver Asphalt Sand Min. Aggregate Location Index Concrete Thickness Base Thickness Thickness" (inches) (inches) (inches) Automobile Parking and Driveways 4.0 3'/8 1 - 1 %2 7.0 Trash Truck & 7.0 3'/s 1 - 1 %z 13.5 Fire Lanes " indicates estimated value 7.12.3 Prior to placing base materials, the subgrade should be scarified to a depth of approximately 12 inches, moisture conditioned to near optimum moisture content, and compacted to a dry density of at least 95 percent of the laboratory maximum dry density as determined by ASTM D 1557. Similarly, the base materials should be compacted to a dry density of at least 95 percent of the laboratory maximum dry density at or slightly above optimum moisture content. 7.12.4 Although the pavers are not intended for stormwater infiltration, consideration should be given to installing a subdrain for the paver sections. The subdrain could be placed at the bottom of the base section below the pavers and the soil subgrade should be graded to allow water to flow to a subdrain. The subdrain should run the distance of the paver area to reduce the potential for water to build up within the paving section. The drain should be connected to an approved drainage device. The drain should consist of a 3-inch diameter perforated Schedule 40, PVC pipe and placed at the bottom of the base materials. 7.12.5 The pavers should be installed and maintained in accordance with the manufacturer's recommendations. Future property owners should be made aware and responsible for the maintenance program. In addition, pavers tend to shift vertically and horizontally during the life of the pavement and should be expected. The pavers normally require a concrete border to prevent lateral movement from traffic. The concrete border surrounding the pavers should be embedded at least 6 inches from finish grade surface to reduce the potential for water migration to the adjacent landscape areas and pavement areas. The pavers should be placed tightly adjacent to each other and the spacing between the paver units should be filled with appropriate filler. A polymer sand (Poly -Sand) can be used on the non -storm water quality paver area to help prevent water infiltration. Geocon Project No. A9799-88-01 - 24 - June 7, 2022 7.10.3 Slabs -on -grade at the ground surface that may receive moisture -sensitive floor coverings or may be used to store moisture -sensitive materials should be underlain by a vapor retarder placed directly beneath the slab. The vapor retarder and acceptable permeance should be specified by the project architect or developer based on the type of floor covering that will be installed. The vapor retarder design should be consistent with the guidelines presented in Section 9.3 of the American Concrete Institute's (ACI) Guide for Concrete Slabs that Receive Moisture -Sensitive Flooring Materials (ACI 302.2R-06) and should be installed in general conformance with ASTM E 1643 (latest edition) and the manufacturer's recommendations. A minimum thickness of 15 mils extruded polyolefm plastic is recommended; vapor retarders which contain recycled content or woven materials are not recommended. The vapor retarder should have a permeabce of less than 0.01 perms demonstrated by testing before and after mandatory conditioning. The vapor retarder should be installed in direct contact with the concrete slab with proper perimeter seal. If the California Green Building Code requirements apply to this project, the vapor retarder should be underlain by 4 inches of clean aggregate. It is important that the vapor retarder be puncture resistant since it will be in direct contact with angular gravel. As an alternative to the clean aggregate suggested in the Green Building Code, it is our opinion that the concrete slab -on -grade may be underlain by a vapor retarder over 4 inches of clean sand (sand equivalent greater than 30), since the sand will serve a capillary break and will minimize the potential for punctures and damage to the vapor barrier. 7.10.4 For seismic design purposes, a coefficient of friction of 0.35 may be utilized between concrete slabs and subgrade soils without a moisture barrier, and 0.15 for slabs underlain by a moisture barrier. 7.10.5 Exterior slabs for walkways or flatwork, not subject to traffic loads, should be at least 4 inches thick and reinforced with No. 3 steel reinforcing bars placed 18 inches on center in both horizontal directions, positioned near the slab midpoint. Prior to construction of slabs, the upper 12 inches of subgrade should be moisture conditioned to near optimum moisture content and properly compacted to at least 95 percent relative compaction, as determined by ASTM Test Method D 1557 (latest edition). Crack control joints should be spaced at intervals not greater than 10 feet and should be constructed using saw -cuts or other methods as soon as practical following concrete placement. Crack control joints should extend a minimum depth of one-fourth the slab thickness. Construction joints should be designed by the project structural engineer. Geocon Project No. A9799-88-01 -21- June 7, 2022 7.10.6 The recommendations of this report are intended to reduce the potential for cracking of slabs due to settlement. However, even with the incorporation of the recommendations presented herein, foundations, stucco walls, and slabs -on -grade may exhibit some cracking due to minor soil movement and/or concrete shrinkage. The occurrence of concrete shrinkage cracks is independent of the supporting soil characteristics. Their occurrence may be reduced and/or controlled by limiting the slump of the concrete, proper concrete placement and curing, and by the placement of crack control joints at periodic intervals, in particular, where re-entrant slab corners occur. 7.11 Preliminary Pavement Recommendations 7.11.1 Where new paving is to be placed, it is recommended that all existing fill and soft alluvium materials be excavated and properly compacted for paving support. The client should be aware that excavation and compaction of all existing artificial fill and soft alluvium in the area of new paving is not required; however, paving constructed over existing uncertified fill or unsuitable alluvium material may experience increased settlement and/or cracking, and may therefore have a shorter design life and increased maintenance costs. As a minimum, the upper 12 inches of paving subgrade should be scarified, moisture conditioned to near optimum moisture content, and properly compacted to at least 95 percent relative compaction, as determined by ASTM Test Method D 1557 (latest edition). 7.1.1.2 The following pavement sections are based on an assumed R-Value of 20. Once site grading activities are complete an R-Value should be obtained by laboratory testing to confirm the properties of the soils serving as paving subgrade, prior to placing pavement. 7.11.3 The Traffic Indices listed below are estimates. Geocon does not practice in the field of traffic engineering. The actual Traffic Index for each area should be determined by the project civil engineer. If pavement sections for Traffic Indices other than those listed below are required, Geocon should be contacted to provide additional recommendations. Pavement thicknesses were determined following procedures outlined in the California Highway Design Manual (Caltrans). It is anticipated that the majority of traffic will consist of automobile and large truck traffic. PRELIMINARY PAVEMENT DESIGN SECTIONS Location Estimated Traffic Asphalt Concrete Class 2 Aggregate Index (TI) (inches) Base (inches) Automobile Parking and Driveways 4.0 3.0 4.0 Trash Truck & Fire Lanes 7.0 4.0 12.0 Geocon Project No. A9799-88-01 -22- 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 OAK INVLS"I'NAEN'I'S 4199 CAMPUS DRIVE IRVI NE, CA 92612 PHONE NO. (714) 342-2502 TF r N Cn Q U Q Z Q Q Z �Q U) W W U) W Ln Ln 06 LO V_ No. Date Description H_C G 00 D U) IseO 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-83