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1 GEOTECHNICAL DUE DILIGENCE FOR PROPOSED RESIDENTIAL DEVELOPMENT AND PARKING STRUCTURES 3800 CHAPMAN AVENUE ORANGE, ORANGE COUNTY, CALIFORNIA PREPARED FOR GREENLAW PARTNERS VON KARMAN AVENUE, SUITE 250 IRVINE, CALIFORNIA PREPARED BY GEOTEK, INC. 710 EAST PARKRIDGE AVENUE, SUITE 105 CORONA, CALIFORNIA PROJECT NO CR FEBRUARY 12, 2016 B-1

2 Greenlaw Partners Von Karman Avenue, Suite 250 Irvine, California February 12, 2016 Attention: Subject: Mr. Scott Murray Geotechnical Due Diligence Proposed Residential Development and Parking Structures 3800 Chapman Avenue Orange, Orange County, California Dear Mr. Murray: We are pleased to provide the results of our geotechnical due diligence for the proposed project located at 3800 Chapman Avenue in Orange, Orange County, California. This report presents the results of our evaluation, discussion of our findings, and provides geotechnical recommendations for foundation design and construction. In our opinion, site development appears feasible from a geotechnical viewpoint provided that the recommendations included in this and future reports by this firm are incorporated into the design and construction phases of the project. The opportunity to be of service is sincerely appreciated. If you should have any questions, please do not hesitate to contact our office. Respectfully submitted, GeoTek, Inc. Edward H. LaMont CEG 1892, Exp. 07/31/16 Principal Geologist Paul Hyun Jin Kim PE 77214, Exp. 06/30/17 Project Engineer Distribution: (1) Addressee via (one PDF file) G:\Projects\1401 to 1450\1435CR Greenlaw Partners 3800 Chapman Avenue Orange\1435 Greenlaw Chapman GEO DD.doc B-2

3 GREENLAW PARTNERS Geotechnical Due Diligence February 12, Chapman Avenue, Orange, Orange County, California Page i TABLE OF CONTENTS 1. PURPOSE AND SCOPE OF SERVICES SITE DESCRIPTION AND PROPOSED DEVELOPMENT SITE DESCRIPTION PROPOSED DEVELOPMENT FIELD EXPLORATION AND LABORATORY TESTING FIELD EXPLORATION LABORATORY TESTING PERCOLATION TEST INFORMATION GEOLOGIC AND SOILS CONDITIONS REGIONAL SETTING GENERAL SOIL CONDITIONS Alluvium SURFACE WATER AND GROUNDWATER Surface Water Groundwater FAULTING AND SEISMICITY Faulting Seismic Design Parameters LIQUEFACTION SEISMICALLY-INDUCED SETTLEMENT OTHER SEISMIC HAZARDS CONCLUSIONS AND RECOMMENDATIONS GENERAL EARTHWORK CONSIDERATIONS General Site Clearing and Preparation Removals Engineered Fill Excavation Characteristics Shrinkage and Bulking Trench Excavations and Backfill DESIGN RECOMMENDATIONS Conventional Slab and Shallow Foundation Design Criteria Miscellaneous Foundation Recommendations Foundation Setbacks Deepened Foundation Design Retaining Wall Design and Constrcution Soil Corrosivity Soil Sulfate Content CONCRETE CONSTRUCTION General Concrete Mix Design B-3

4 GREENLAW PARTNERS Geotechnical Due Diligence February 12, Chapman Avenue, Orange, Orange County, California Page ii TABLE OF CONTENTS Concrete Flatwork Concrete Performance POST CONSTRUCTION CONSIDERATION Irrigation Drainage PLAN REVIEW AND CONSTRUCTION OBSERVATIONS INTENT LIMITATIONS SELECTED REFERENCES ENCLOSURES Figure 1 Site Location Map Figure 2 Boring Location Map Appendix A Logs of Exploratory Borings Appendix B Results of Laboratory Testing Appendix C Seismic Settlement Potential Evaluation Output Appendix D Pile Capacity Output Appendix E General Earthwork Grading Guidelines B-4

5 GREENLAW PARTNERS Geotechnical Due Diligence February 12, Chapman Avenue, Orange, Orange County, California Page 1 1. PURPOSE AND SCOPE OF SERVICES The purpose of this study was to evaluate the geotechnical conditions in the immediate vicinity of proposed site construction. Services provided for this study included the following: Research and review of available geologic data and general information pertinent to the site; Site exploration consisting of the excavation, logging, and sampling of two exploratory borings; Laboratory testing of soil samples collected during the field investigation; Review and evaluation of site seismicity; and Compilation of this geotechnical report which presents our findings, conclusions, and recommendations for this site. When site construction plans become more finalized, additional field exploration, lab testing, engineering analysis and foundation design recommendations may be necessary. 2. SITE DESCRIPTION AND PROPOSED DEVELOPMENT 2.1 SITE DESCRIPTION The site is located at 3800 Chapman Avenue in Orange, California. The subject property is situated on the south side of Chapman Avenue, east of the intersection with Lewis Street (Figure 1). The irregular shaped parcel is approximately 5.8 acres in size and is relatively level with an approximate maximum elevation difference of 3 feet sloping down to the west and south. The site is presently developed with a multi-story commercial buildings situated on the northeast corner of the site. The remaining portion of the site is developed with asphalt parking. Some minor landscaping is present along the property lines and within the parking aisles. B-5

6 GREENLAW PARTNERS Geotechnical Due Diligence February 12, Chapman Avenue, Orange, Orange County, California Page 2 The site is bounded to the north by Chapman Avenue. The adjacent properties to the west and east are developed with a retail and commercial buildings, respectively. The site is immediately bounded to the west and east by asphalt parking and drive aisles. The adjacent property to the south is developed with three-story multi-family structures. The closest adjacent structure is a carport situated as close as approximately 7 feet from the property line. 2.2 PROPOSED DEVELOPMENT Based on a site plan prepared by KTGY Group, Inc., dated December 16, 2015, the proposed development will consist of a 5-story residential wrap building. A 7-story parking structure is proposed within the residential wrap building. In addition, a 5-level parking structure is proposed along the southeast portion of the property. Specific structural loading has not been provided. Once structural loading is finalized, GeoTek should be provided with them so that additional analysis may be performed. Additionally, a grading plan has also not been provided but this report is based on that final grades will be within +3 feet of existing grades. If the site development differs from the project information presented in this report, the recommendations presented in this report will likely further review and evaluation. 3. FIELD EXPLORATION AND LABORATORY TESTING 3.1 FIELD EXPLORATION The field exploration for this investigation was conducted on January 6, 2016 and consisted of excavating two exploratory borings with the aid of a truck mounted drill rig to depths of 11½ feet to 51½ feet. The borings were drilled within the proposed development area as shown on the attached Boring Location Map (Figure 2). An engineer from our firm logged the excavations and collected soil samples for use in subsequent laboratory testing. The logs of the exploratory borings are included in Appendix A. B-6

7 GREENLAW PARTNERS Geotechnical Due Diligence February 12, Chapman Avenue, Orange, Orange County, California Page LABORATORY TESTING Laboratory testing was performed on selected bulk and relatively undisturbed samples collected during the field exploration. The purpose of the laboratory testing was to confirm the field classification of the materials encountered and to evaluate their physical properties for use in the engineering design and analysis. Results of the laboratory testing program along with a brief description and relevant information regarding testing procedures are included in Appendix B. 3.3 PERCOLATION TEST INFORMATION As requested, GeoTek performed a percolation (infiltration) test within soil boring P-1 at the subject site at the approximate location indicated on Figure 2. Percolation testing was conducted to an approximate depth of 11½ feet below existing grade (bgs). The boring diameter was approximately 8 inches. Approximately 2 inches of gravel was placed on the bottom of the boring excavation. A 3-inch diameter perforated PVC pipe, wrapped in filter sock was placed in the boring excavation and the annular space was filled with gravel to prevent caving within the boring. The boring was then filled with water to pre-soak the hole. After the presoaking period, the percolation test was then performed. The results were converted to an infiltration rate via the Porchet Method as per jurisdictional guidelines (Technical Guidance Document by the County of Orange, 2011). Based on the results of our testing, the test location has an infiltration rate of approximately 0.7 in/hr. Note that variations may occur within the site and with depth. As a result, we recommend that an appropriate factor of safety be applied to account for these conditions. 4. GEOLOGIC AND SOILS CONDITIONS 4.1 REGIONAL SETTING The site is situated in the Peninsular Ranges province, which is one of the largest geomorphic units in western North America. Basically, it extends from the Transverse Ranges geomorphic province and the Los Angeles Basin, approximately 900 miles south to the tip of Baja California. This province varies in width from about 30 to 100 miles. It is bounded on the west by the Pacific Ocean, on the south by the Gulf of California and on the east by the Colorado Desert Province. B-7

8 GREENLAW PARTNERS Geotechnical Due Diligence February 12, Chapman Avenue, Orange, Orange County, California Page 4 The Peninsular Ranges are essentially a series of northwest-southeast oriented fault blocks. Three major fault zones are found in this province. The Elsinore Fault zone and the San Jacinto Fault zone trend northwest-southeast and are found near the middle of the province. The San Andreas Fault zone borders the northeasterly margin of the province. More specific to the property, the site is located in an area geologically mapped to be underlain by alluvial fan deposits (Morton and Miller, 2006). 4.2 GENERAL SOIL CONDITIONS A brief description of the earth materials encountered is presented in this section. Based on our site reconnaissance, our exploratory excavations and review of published geologic maps, the area investigated is locally underlain by alluvial materials. Some near surface fill materials are also likely to exist across the project site based on the presence of existing site improvements Alluvium Alluvium was observed in both borings. The alluvium generally consists of loose to medium dense sand. Interlayers of sandy clay and clay were observed in the alluvium. The materials were observed to possess a very low expansion potential. Layers of sandy clay was observed in the upper portions of the alluvium in boring P SURFACE WATER AND GROUNDWATER Surface Water If encountered during the earthwork construction, surface water on this site is the result of precipitation or possibly some minor surface run-off from the surrounding areas. Overall site area drainage is in west and southerly direction. Provisions for surface drainage will need to be accounted for by the project civil engineer Groundwater Water was not encountered in our exploratory excavations. Historic high groundwater is mapped at greater than 50 feet below ground surface (bgs) by the CGS. It is possible that seasonal variations (temperature, rainfall, etc.) will cause fluctuations in the groundwater level. Additionally, perched water may be encountered in discontinuous zones within the overburden. The groundwater levels presented in this report are the levels that B-8

9 GREENLAW PARTNERS Geotechnical Due Diligence February 12, Chapman Avenue, Orange, Orange County, California Page 5 were measured at the time of our field activities or as stated in the referenced source. It is recommended that the contractor determine the actual groundwater levels at the site at the time of the construction activities to determine the impact, if any, on the construction procedures. 4.4 FAULTING AND SEISMICITY Faulting The geologic structure of the entire California area is dominated mainly by northwest-trending faults associated with the San Andreas system. The site is in a seismically active region. No active or potentially active fault is known to exist at this site nor is the site situated within a State of California designated Alquist-Priolo Earthquake Fault Zone. The nearest zone fault is the Newport-Inglewood fault zone and the Whittier Fault, located approximately 9½ miles and 10 miles to the southwest and northeast, respectively Seismic Design Parameters The site is located at approximately latitude: N and longitude: W. Site spectral accelerations (Ss and S1), for 0.2 and 1.0 second periods for a Class D site, were determined from the USGS Website, Earthquake Hazards Program, U.S. Seismic Design Maps for Risk-Targeted Maximum Considered Earthquake (MCE R ) Ground Motion Response Accelerations for the Conterminous 48 States by Latitude/Longitude. The results are presented in the following table: SITE SEISMIC PARAMETERS Mapped 0.2 sec Period Spectral Acceleration, Ss Mapped 1.0 sec Period Spectral Acceleration, S g 0.540g Site Coefficient for Site Class C, Fa 1.0 Site Coefficient for Site Class C, Fv 1.5 Maximum Considered Earthquake Spectral Response Acceleration for 0.2 Second, SMS 1.481g Maximum Considered Earthquake Spectral Response Acceleration for 1.0 Second, SM g 5% Damped Design Spectral Response Acceleration Parameter at 0.2 Second, SDS 0.987g 5% Damped Design Spectral Response Acceleration Parameter at 1 second, SD g B-9

10 GREENLAW PARTNERS Geotechnical Due Diligence February 12, Chapman Avenue, Orange, Orange County, California Page 6 Final selection of the appropriate seismic design coefficients should be made by the project structural engineer based upon the local practices and ordinances, expected building response and desired level of conservatism. 4.5 LIQUEFACTION Liquefaction describes a phenomenon in which cyclic stresses, produced by earthquakeinduced ground motion, create excess pore pressures in relatively cohesionless soils. These soils may thereby acquire a high degree of mobility, which can lead to lateral movement, sliding, consolidation and settlement of loose sediments, sand boils and other damaging deformations. This phenomenon occurs only below the water table, but, after liquefaction has developed, the effects can propagate upward into overlying non-saturated soil as excess pore water dissipates. The factors known to influence liquefaction potential include soil type and grain size, relative density, groundwater level, confining pressures, and both intensity and duration of ground shaking. In general, materials that are susceptible to liquefaction are loose, saturated granular soils having low fines content under low confining pressures. The subject site is not mapped within a zone of potentially liquefiable soils by the Department of Conservation (CGS). Liquefaction is not considered a hazard at the site due to great depth to groundwater (greater than 50 feet) and the underlying dense nature of the subsurface soils. 4.6 SEISMICALLY-INDUCED SETTLEMENT Seismic-induced settlement can occur both above and below the groundwater table during a strong seismic event. Settlement below the groundwater table during a strong seismic event occurs in response to liquefaction. The standard penetration data from the borings excavated on the site, provided input for the LiquefyPro Version 5 program for seismic induced settlement. The results of this evaluation are shown in Appendix C, and reveal a seismic settlement potential of 2¾ inches with an estimated 1.4 inches of differential settlement across a 40 feet span. We recommend that the structural engineer evaluate the seismic-induced settlement and determine the impact on the existing and/or proposed improvements. 4.7 OTHER SEISMIC HAZARDS Evidence of ancient landslides or slope instabilities at this site was not observed during our investigation. Thus, the potential for landslides is considered negligible. B-10

11 GREENLAW PARTNERS Geotechnical Due Diligence February 12, Chapman Avenue, Orange, Orange County, California Page 7 The potential for secondary seismic hazards such as a seiche and tsunami are considered to be negligible due to site elevation and distance from an open body of water. 5. CONCLUSIONS AND RECOMMENDATIONS 5.1 GENERAL The proposed development appears feasible from a geotechnical viewpoint provided that the following recommendations are incorporated into design and construction. Structural loading was not provided for the structures. The proposed residential wrap structure is anticipated to be of wood-frame construction. As a result, the residential structure may be supported with shallow conventional foundations bearing into engineered fill. Overexcavation and recompaction is recommended below foundation elements to provide a uniform bearing material beneath the planned footings and slabs. The proposed parking structures are anticipated to be supported with a deepened foundation system due to its heavy loads. Preliminary recommendations are provided below for foundations in the vicinity of our soil boring. Once structural loads are finalized, GeoTek should be provided with the information, so that the recommendations provided herein, may be re-evaluated. 5.2 EARTHWORK CONSIDERATIONS General Earthwork and grading should be performed in accordance with the applicable grading ordinances of the City of Orange, the 2013 California Building Code (CBC), and recommendations contained in this report. The Grading Guidelines included in Appendix E outline general procedures and do not anticipate all site specific situations. In the event of conflict, the recommendations presented in the text of this report should supersede those contained in Appendix E Site Clearing and Preparation Site preparation should commence with removal of deleterious materials and vegetation and the demolition of the existing improvements. Demolition should include removal of the B-11

12 GREENLAW PARTNERS Geotechnical Due Diligence February 12, Chapman Avenue, Orange, Orange County, California Page 8 existing improvements and other below-grade construction. Existing underground utilities should either be properly capped off at the property boundaries and removed or be re-routed around the new development. All soils disturbed by the demolition and clearing operations should be removed and stockpiled on-site for future use as engineered fill. All debris and deleterious materials generated by the site stripping and demolition operations should be legally disposed off-site Removals The upper 24 inches of the existing earth materials should be removed and replaced with engineered fill. All existing fill materials encountered in proposed structural areas or supporting structural areas, should be removed. In areas of the proposed residential buildings and improvements, a minimum of 3 feet of engineered fill below the bottom of the proposed footings and floor-slabs should be provided. A minimum of 2 feet of fill should be provided beneath the pavement subgrade. The lateral extent of removals should extend at least 5 feet outside the footings and floorslabs, or a distance equal to the depth of overexcavation below the bottom of the structural elements, whichever is greater. A representative of this firm should observe the bottom of all excavations. Upon approval, the exposed subgrade should be scarified to a depth of approximately 6 inches, moistened to at least the optimum moisture content and compacted to a minimum relative compaction of 90 percent (ASTM D1557) Engineered Fill On-site materials are generally considered suitable for reuse as engineered fill provided they are free from vegetation, roots, and other deleterious material. Rock fragments greater than 6 inches in maximum dimension should not be incorporated into engineered fill. Engineered fill materials should be placed in horizontal lifts not exceeding 8 inches in loose thickness, moisture conditioned to at least the optimum moisture content and compacted to a minimum relative compaction of 90% (ASTM D 1557). The upper 12 inches of pavement subgrade should be compacted to 95% Excavation Characteristics Excavation in the on-site soils is expected to be feasible utilizing heavy-duty grading equipment in good operating condition. All temporary excavations for grading purposes and installation of underground utilities should be constructed in accordance with local and Cal-OSHA guidelines. B-12

13 GREENLAW PARTNERS Geotechnical Due Diligence February 12, Chapman Avenue, Orange, Orange County, California Page 9 Temporary vertical excavations within the on-site materials should be stable vertically up to 4 feet or to 3½ feet with a 1:1 (horizontal: vertical) cut above Shrinkage and Bulking Several factors will impact earthwork balancing on the site, including shrinkage, subsidence, trench spoil from utilities and footing excavations, as well as the accuracy of topography. Shrinkage and subsidence are primarily dependent upon the degree of compactive effort achieved during construction, depth of fill and underlying site conditions. For planning purposes, a shrinkage factor of up to 5 to 15 percent may be considered for the materials requiring removal and recompaction. Site balance areas should be available in order to adjust project grades, depending on actual field conditions at the conclusion of site earthwork construction. Subsidence on the order of 0.1 feet may occur Trench Excavations and Backfill Trench excavations should conform to Cal-OSHA regulations. The contractor should have a competent person, per OSHA requirements, on site during construction to observe conditions and to make the appropriate recommendations. Utility trench backfill should consist of sandy soil with a very low expansion potential and compacted to at least 90% relative compaction (as determined per ASTM D 1557). Where applicable, based on jurisdictional requirements, the top 12 inches of backfill below subgrade for road pavements should be compacted to at least 95 percent relative compaction. Compaction should be achieved with a mechanical compaction device. Jetting of trench backfill is not recommended. If soils to be used as backfill have dried out, they should be thoroughly moisture conditioned prior to placement in trenches. 5.3 DESIGN RECOMMENDATIONS Preliminary foundation design criteria for on-grade slabs, conventional foundations and deepened foundations are presented in this report. These are typical design criteria and are not intended to supersede the design by the structural engineer Conventional Slab and Shallow Foundation Design Criteria Preliminary design criteria for a conventional foundation system, in general conformance with the 2013 CBC, are presented for the proposed structure bearing into engineered fill. It is anticipated that the onsite materials would possess a very low expansion potential. Additional testing should be completed subsequent to rough grading to confirm this. These B-13

14 GREENLAW PARTNERS Geotechnical Due Diligence February 12, Chapman Avenue, Orange, Orange County, California Page 10 are typical design criteria and are not intended to supersede the design by the structural engineer. A summary of our preliminary conventional foundation design recommendations is tabulated below: GEOTECHNICAL RECOMMENDATIONS FOR FOUNDATION DESIGN DESIGN PARAMETER 0<EI<20 Foundation Depth or Minimum Perimeter Beam Depth (inches below lowest adjacent grade) 18 Minimum Foundation Width (inches)* 15 Minimum Slab Thickness (inches) Sand Blanket and Moisture Retardant Membrane Below On-Grade Building Slabs Minimum Slab Reinforcing Minimum Reinforcement for Continuous Footings, Grade Beams and Retaining Wall Footings Presaturation of Subgrade Soil (Percent of Optimum/Depth in Inches) * Code minimums per Table of the 2013 CBC ** Sand should have a Sand Equivalent of at least 30 5 (actual) 2 inches of sand** overlying moisture vapor retardant membrane overlying 2 inches of sand** No. 3 rebar 24 on-center, each way, placed in middle of slab Four No. 4 reinforcing Bars, two placed near the top and two near the bottom Minimum of 110% of the optimum moisture content to a depth of at least 12 inches prior to placing concrete *** Effective plasticity index should be verified at the completion of grading It should be noted that the above recommendations are based on soil support characteristics only. The structural engineer should design the slab and beam reinforcement based on actual loading conditions. The following criteria for design of foundations should be implemented: An allowable bearing capacity of 3,000 pounds per square foot (psf) may be used for design of continuous footings 18 inches deep and 12 inches wide, and pad footings 24 inches square and 18 inches deep. This value may be increased by 350 pounds per square foot for each additional 12 inches in depth and 250 pounds per square foot for each additional 12 inches in width to a maximum value of 4,000 psf. Additionally, an increase of one-third may be applied when considering short-term live loads (e.g. seismic and wind loads). B-14

15 GREENLAW PARTNERS Geotechnical Due Diligence February 12, Chapman Avenue, Orange, Orange County, California Page The recommended allowable bearing capacity is based on a total post-construction settlement of one (1) inch. Differential settlement of up to one-half of the total settlement over a horizontal distance of 40 feet could result Spread footings for an individual structure should be tied together in two orthogonal directions with either reinforced grade-beams and/or continuous footings to provide a more rigid and monolithic shallow foundation system The passive earth pressure may be computed as an equivalent fluid having a density of 300 psf per foot of depth, to a maximum earth pressure of 3,000 psf for footings founded in engineered fill. A coefficient of friction between engineered fill and concrete of 0.40 may be used with dead load forces. When combining passive pressure and frictional resistance, the passive pressure component should be reduced by one-third A grade beam, 12 inches wide by 18 inches deep (minimum), should be utilized across large openings. The base of the grade beam should be at the same elevation as the bottom of the adjoining footings A moisture and vapor retarding system should be placed below slabs-on-grade where moisture migration through the slab is undesirable. Guidelines for these systems are provided in the 2013 California Green Building Standards Code (CALGreen) Section and the 2013 CBC Section and ACI 360R-10. The vapor retarder design and construction should also meet the requirements of ASTM E1643. A portion of the vapor retarder design should be the implementation of a moisture vapor retardant membrane. It should be realized that the effectiveness of the vapor retarding membrane can be adversely impacted as a result of construction related punctures (e.g. stake penetrations, tears, punctures from walking on the aggregate layer, etc.). These occurrences should be limited as much as possible during construction. Thicker membranes are generally more resistant to accidental puncture than thinner ones. Products specifically designed for use as moisture/vapor retarders may also be more puncture resistant. Although the CBC specifies a 6 mil vapor retarder membrane, it is GeoTek s opinion that a minimum 10 mil thick membrane with joints properly overlapped and sealed should be considered, unless otherwise specified by the slab design professional. The membrane should consist of Stego wrap or the equivalent. B-15

16 GREENLAW PARTNERS Geotechnical Due Diligence February 12, Chapman Avenue, Orange, Orange County, California Page 12 Moisture and vapor retarding systems are intended to provide a certain level of resistance to vapor and moisture transmission through the concrete, but do not eliminate it. The acceptable level of moisture transmission through the slab is to a large extent based on the type of flooring used and environmental conditions. Ultimately, the vapor retarding system should be comprised of suitable elements to limit migration of water and reduce transmission of water vapor through the slab to acceptable levels. The selected elements should have suitable properties (i.e., thickness, composition, strength, and permeability) to achieve the desired performance level. Consideration should be given to consulting with an individual possessing specific expertise in this area for additional evaluation. Moisture retarders can reduce, but not eliminate, moisture vapor rise from the underlying soils up through the slab. Moisture retarders should be designed and constructed in accordance with applicable American Concrete Institute, Portland Cement Association, Post-Tensioning Concrete Institute, ASTM and California Building Code requirements and guidelines. GeoTek recommends that a qualified person, such as the flooring contractor, structural engineer, and/or architect be consulted to evaluate the general and specific moisture vapor transmission paths and any impact on the proposed construction. That person (or persons) should provide recommendations for mitigation of potential adverse impact of moisture vapor transmission on various components of the structures as deemed appropriate. In addition, the recommendations in this report and our services in general are not intended to address mold prevention, since we along with geotechnical consultants in general, do not practice in areas of mold prevention. If specific recommendations are desired, a professional mold prevention consultant should be contacted We recommend that control joints be placed in two orthogonal directions spaced approximately 24 to 36 times the thickness of the slab in inches. These joints are a widely accepted means to control cracks and should be reviewed by the project structural engineer Miscellaneous Foundation Recommendations Isolated exterior footings should be tied back to the main foundation system in two orthogonal directions. B-16

17 GREENLAW PARTNERS Geotechnical Due Diligence February 12, Chapman Avenue, Orange, Orange County, California Page To reduce moisture penetration beneath the slab on grade areas, utility trenches should be backfilled with engineered fill, lean concrete or concrete slurry where they intercept the perimeter footing or thickened slab edge Soils from the footing excavations should not be placed in the slab-on-grade areas unless properly compacted and tested. The excavations should be free of loose/sloughed materials and be neatly trimmed at the time of concrete placement Foundation Setbacks Where applicable, the following setbacks should apply to all foundations. Any improvements not conforming to these setbacks may be subject to lateral movements and/or differential settlements: The bottom of all footings for structures near retaining walls should be deepened so as to extend below a 1:1 projection upward from the bottom inside edge of the wall stem. This applies to the existing retaining walls along the perimeter, if they are to remain. The bottom of any existing foundations for structures should be deepened so as to extend below a 1:1 projection upward from the bottom of the nearest excavation Deepened Foundation Design Due to the expected heavy loads from a multi-story parking structure, a deep foundation system consisting of drilled piers is anticipated. The allowable axial capacities provided in Appendix D for the drilled piers were calculated based on the values for shaft resistance and end bearing capacity of the piers in the vicinity of our soil boring for 24- and 36-inch diameters and 30 feet long. The allowable axial capacities provided include a factor of safety of 3 for end bearing and 2 for skin friction. For skin friction calculations, the top 5 feet of soil was ignored. Once design loads are known, capacities for other size (diameter and length) piers or other deep foundation types (driven piles or auger-cast piles) can be determined, upon request. Dependent upon the structural loads to be applied, additional explorations may be warranted. Drilled piers may be installed on a spacing of 3 pile diameters (center to center) with no reduction in capacity for group effects. Pier capacities for compressive and uplift loading may be increased by ⅓ for temporary wind and/or seismic loading conditions. Piers installed on a spacing of 2 pier diameters (center to center) can generally be reduced by 30 percent for group effects, however, to give a more accurate number, we should be provided with more detailed group spacing. B-17

18 GREENLAW PARTNERS Geotechnical Due Diligence February 12, Chapman Avenue, Orange, Orange County, California Page 14 Each pier should be drilled and concrete placed the same day. Piers that are to be placed closer than 2.5 diameters center to center should be constructed on different days. Surface run-off water should be drained away from the excavations and not be allowed to pond. If it is required that foundation excavations be left open for more than one day, they should be properly covered to prevent personal injury and fall hazards, and be protected to reduce evaporation or entry of moisture. The portion of the pier above the water table should be reamed out the following day. If concrete is placed within an excavation containing groundwater, it should be placed from the bottom of the excavation using a tremie or similar method. This is intended to allow the concrete to displace groundwater as it is placed Retaining Wall Design and Constrcution General Design Criteria Recommendations presented in this report apply to typical masonry or concrete retaining walls to a maximum height of up to 6 feet. Additional review and recommendations should be requested for higher walls. These are typical design criteria and are not intended to supersede the design by the structural engineer. Retaining wall foundations should be embedded a minimum of 18 inches into engineered fill and should be designed in accordance with Section of this report. Structural needs may govern and should be evaluated by the project structural engineer. All earth retention structure plans, as applicable, should be reviewed by this office prior to finalization. Earthwork considerations, site clearing and remedial earthwork for all earth retention structures should meet the requirements of this report, unless specifically provided otherwise, or more stringent requirements or recommendations are made by the designer. The backfill material placement for all earth retention structures should meet the requirement of Section in this report. In general, cantilever earth retention structures, which are designed to yield at least 0.001H, where H is equal to the height of the earth retention structure to the base of its footing, may be designed using the active condition. Rigid earth retention structures (including but not limited to rigid walls, and walls braced at top, such as typical basement walls) should be designed using the at-rest condition. B-18

19 GREENLAW PARTNERS Geotechnical Due Diligence February 12, Chapman Avenue, Orange, Orange County, California Page 15 In addition to the design lateral forces due to retained earth, surcharges due to improvements, such as an adjacent building or traffic loading, should be considered in the design of the earth retention structures. Loads applied within a 1:1 (h:v) projection from the surcharge on the stem and footing of the earth retention structure should be considered in the design. Final selection of the appropriate design parameters should be made by the designer of the earth retention structures Cantilevered Walls The recommendations presented below are for cantilevered retaining walls up to 10 feet high. Active earth pressure may be used for retaining wall design, provided the top of the wall is not restrained from minor deflections. An equivalent fluid pressure approach may be used to compute the horizontal pressure against the wall. Appropriate fluid unit weights are given below for specific slope gradients of the retained material. These do not include other superimposed loading conditions such as traffic, structures, seismic events, or adverse geologic conditions. ACTIVE EARTH PRESSURES Surface Slope of Retained Equivalent Fluid Pressure Materials (pcf) (h:v) Select Backfill* Level 30 2:1 45 *The design pressures assume the backfill material has an expansion index less than or equal to 20. Backfill zone includes area between back of the wall to a plane (1:1 h:v) up from bottom of the wall foundation (on the backside of the wall) to the (sloped) ground surface Restrained Retaining Walls Retaining walls that will be restrained at the top that support level backfill or that have reentrant or male corners, should be designed for an equivalent at-rest fluid pressure of 55 pcf, plus any applicable surcharge loading. For areas of male or reentrant corners, the restrained wall design should extend a minimum distance of twice the height of the wall laterally from the corner, or a distance otherwise determined by the project structural engineer. B-19

20 GREENLAW PARTNERS Geotechnical Due Diligence February 12, Chapman Avenue, Orange, Orange County, California Page Retaining Wall Backfill and Drainage Retaining walls should be provided with an adequate pipe and gravel back drain system to help prevent buildup of hydrostatic pressures. Backdrains should consist of a 4-inch diameter perforated collector pipe (Schedule 40, SDR 35, or approved equivalent) embedded in a minimum of one (1) cubic foot per linear foot of ¾- to 1-inch clean crushed rock or an approved equivalent, wrapped in filter fabric (Mirafi 140N or an approved equivalent). The drain system should be connected to a suitable outlet. Waterproofing of site walls should be performed where moisture migration through the wall is undesirable. Retaining wall backfill should be placed in lifts no greater than eight (8) inches in thickness and compacted to a minimum of 90% relative compaction in accordance with ASTM Test Method D The wall backfill should also include a minimum one (1) foot wide section of ¾- to 1-inch clean crushed rock (or an approved equivalent). The rock should be placed immediately adjacent to the back of the wall and extend up from a back drain to within approximately 24 inches of the finish grade. The rock should be separated from the earth with filter fabric. The upper 24 inches should consist of compacted on-site soil. As an alternative to the drain rock and fabric, Miradrain 2000, or approved equivalent, may be used behind the retaining wall. The Miradrain 2000 should extend from the base of the wall to within 2 feet of the ground surface. The subdrain should be placed at the base of the wall in direct contact with the Miradrain The presence of other materials might necessitate revision to the parameters provided and modification of the wall designs. Proper surface drainage needs to be provided and maintained Other Design Considerations Wall design should consider the additional surcharge loads from superjacent slopes and/or footings, where appropriate. No backfill should be placed against concrete until minimum design strengths are evident by compression tests of cylinders. The retaining wall footing excavations, backcuts, and backfill materials should be approved the project geotechnical engineer or their authorized representative Soil Corrosivity The soil resistivity at this site was tested in the laboratory on one sample collected during the field investigation. The results of the testing (minimum resistivity = 4,200 ohm-cm) indicate B-20

21 GREENLAW PARTNERS Geotechnical Due Diligence February 12, Chapman Avenue, Orange, Orange County, California Page 17 that the on-site soils are considered corrosive to buried ferrous metal in accordance with current standards used by corrosion engineers. We recommend that a corrosion engineer be consulted to provide recommendations for the protection of buried ferrous metal at this site Soil Sulfate Content The sulfate content was determined in the laboratory for one on-site soil sample. The results indicate that the water soluble sulfate result is less than 0.1 percent by weight, which is considered not applicable (negligible) as per Table of ACI CONCRETE CONSTRUCTION General Concrete construction should follow the 2013 CBC and ACI guidelines regarding design, mix placement and curing of the concrete. If desired, we could provide quality control testing of the concrete during construction Concrete Mix Design As indicated in Section 5.3.6, no special concrete mix design is required by Code to resist sulfate attack based on the existing test results. However, additional testing should be performed during grading so that specific recommendations can be formulated based on the asgraded conditions Concrete Flatwork Exterior concrete flatwork is often one of the most visible aspects of site development. They are typically given the least level of quality control, being considered non-structural components. Cracking of these features is fairly common due to various factors. While cracking is not usually detrimental, it is unsightly. We suggest that the same standards of care be applied to these features as to the structure itself. Flatwork may consist of 4-inch thick concrete and the use of reinforcement is suggested. The project structural engineer should provide final design recommendations Concrete Performance Concrete cracks should be expected. These cracks can vary from sizes that are essentially unnoticeable to more than 1/8 inch in width. Most cracks in concrete while unsightly do not significantly impact long-term performance. While it is possible to take measures (proper concrete mix, placement, curing, control joints, etc.) to reduce the extent and size of cracks that occur, some cracking will occur despite the best efforts to minimize it. Concrete B-21

22 GREENLAW PARTNERS Geotechnical Due Diligence February 12, Chapman Avenue, Orange, Orange County, California Page 18 undergoes chemical processes that are dependent on a wide range of variables, which are difficult, at best, to control. Concrete, while seemingly a stable material, is subject to internal expansion and contraction due to external changes over time. One of the simplest means to control cracking is to provide weakened control joints for cracking to occur along. These do not prevent cracks from developing; they simply provide a relief point for the stresses that develop. These joints are a widely accepted means to control cracks but are not always effective. Control joints are more effective the more closely spaced they are. GeoTek suggests that control joints be placed in two directions and located a distance apart approximately equal to 24 to 36 times the slab thickness. 5.5 POST CONSTRUCTION CONSIDERATION Irrigation Control of irrigation water is a necessary part of site maintenance. Soggy ground, near-surface perched water, or seeps may result if irrigation water is excessively or improperly applied. All irrigation systems should be adjusted to provide the minimum water needed to sustain landscaping and prevent excessive drying of the soils. Generally significant runoff during an irrigation cycle indicates excessive irrigation, while soils which dry to a depth of more than several inches between irrigation cycles indicate inadequate irrigation. Adjustments should be made for changes in the climate and rainfall. Irrigation should stop when sufficient water is provided by precipitation. It is important to avoid repeated wetting and drying of the slope surface, which may cause the soil to crack, loosen and/or slowly move laterally (creep) downslope. Landscaping and irrigation will reduce repeated wetting and drying of the slopes. It is important to maintain uniform soil moisture conditions adjacent to the structure to reduce soil expansion and shrinkage that can cause cracking to the structure. Irrigation should be utilized to prevent the soils from drying to a depth more than several inches. Broken, leaking or plugged sprinklers or irrigation lines should be repaired immediately. Frequent inspections of the irrigation systems should be performed. It is common for planting to be placed adjacent to structures in planter or lawn areas. This will result in the introduction of water into the ground adjacent to the foundation. This type of landscaping should be avoided. If used, then extreme care should be exercised with regard to B-22

23 GREENLAW PARTNERS Geotechnical Due Diligence February 12, Chapman Avenue, Orange, Orange County, California Page 19 the irrigation and drainage in these areas. Waterproofing of the foundation and/or subdrains may be necessary and advisable Drainage The need to maintain proper surface drainage and subsurface systems cannot be overly emphasized. Positive site drainage should be maintained at all times. Drainage should not flow uncontrolled down any descending slope. Water should be directed away from foundations and not allowed to pond or seep into the ground adjacent to the footings. Soil areas within 10 feet of the proposed structure should slope at a minimum of 5 percent away from the building, if possible unless the area is paved. Paved areas are to be sloped at 2 percent away from the structure. Roof gutters and downspouts should discharge onto paved surfaces sloping away from the structure or into a closed pipe system which outfalls to the street gutter pan or directly to the storm drain system. Pad drainage should be directed toward approved areas and not be blocked by other improvements. It is the owner s responsibility to maintain and clean drainage devices on or contiguous to their lot. In order to be effective, maintenance should be conducted on a regular and routine schedule and necessary corrections made prior to each rainy season. 5.6 PLAN REVIEW AND CONSTRUCTION OBSERVATIONS We recommend that site grading, specifications, and foundation plans be reviewed by this office prior to construction to check for conformance with the recommendations of this report. We also recommend that GeoTek representatives be present during site grading and foundation construction to observe and document for proper implementation of the geotechnical recommendations. The owner/developer should have GeoTek perform at least the following duties: Observe site clearing and grubbing operations for proper removal of all unsuitable materials. Observe and test bottom of removals prior to fill placement. Evaluate the suitability of on-site and import materials for fill placement, and collect soil samples for laboratory testing where necessary. Observe the fill for uniformity during placement including utility trenches. Also, test the fill for field density, relative compaction and moisture content. Observe and probe foundation excavations to confirm suitability of bearing materials. Observe drilled pier excavations. B-23

24 GREENLAW PARTNERS Geotechnical Due Diligence February 12, Chapman Avenue, Orange, Orange County, California Page 20 Observed retaining wall subdrain. If requested, a construction observation and compaction report can be provided by GeoTek which can comply with the requirements of the governmental agencies having jurisdiction over the project. We recommend that these agencies be notified prior to commencement of construction so that necessary grading permits can be obtained 6. INTENT It is the intent of this report to aid in the design and construction of the proposed development. Implementation of the advice presented in this report is intended to reduce risk associated with construction projects. The professional opinions and geotechnical advice contained in this report are not intended to imply total performance of the project or guarantee that unusual or variable conditions will not be discovered during or after construction. The scope of our evaluation is limited to the area explored that is shown on the Boring Location Map (Figure 2). This evaluation does not and should in no way be construed to encompass any areas beyond the specific area of the proposed construction as indicated to us by the client. Further, no evaluation of any existing site improvements is included. The scope is based on our understanding of the project and the client s needs, our proposal (Proposal No. P ) dated June 23, 2015 and geotechnical engineering standards normally used on similar projects in this region. 7. LIMITATIONS Our findings are based on site conditions observed and the stated sources. Thus, our comments are professional opinions that are limited to the extent of the available data. GeoTek has prepared this report in a manner consistent with that level of care and skill ordinarily exercised by members of the engineering and science professions currently practicing under similar conditions in the jurisdiction in which the services are provided, subject to the time limits and physical constraints applicable to this report. B-24

25 GREENLAW PARTNERS Geotechnical Due Diligence February 12, Chapman Avenue, Orange, Orange County, California Page 21 Since our recommendations are based on the site conditions observed and encountered, and laboratory testing, our conclusions and recommendations are professional opinions that are limited to the extent of the available data. Observations during construction are important to allow for any change in recommendations found to be warranted. These opinions have been derived in accordance with current standards of practice and no warranty of any kind is expressed or implied. Standards of care/practice are subject to change with time. 8. SELECTED REFERENCES American Concrete Institute (ACI), 2006, Publication 302.2R-06, Guide for Concrete Slabs That Receive Moisture Sensitive Flooring Materials., 2010, Publications 360R-10, Guide to Design of Slabs-On-Ground. Bryant, W.A., and Hart, E.W., 2007, Fault Rupture Hazard Zones in California, Alquist-Priolo Earthquake Fault Zoning Act with Index to Earthquake Fault Zones Maps, California Geological Survey: Special Publication 42. California Code of Regulations, Title 24, 2013 California Building Code, 3 volumes. California Division of Mines and Geology, 1997, Seismic Hazard Zone Report for the Anaheim and Newport Beach Quadrangles, Orange County, Califonria, SHZR-03. GeoTek, Inc., In-house proprietary information. Morton and Miller, 2006, Geologic Map of the San Bernardino and Santa Ana 30' x 60' Quadrangles, USGS, OF , Scale 1:100,000. Seismic Design Values for Buildings ( B-25

26 APPROXIMATE SITE AREA Greenlaw Partners 3800 Chapman Avenue City of Orange Orange County, California GeoTek Figure 1 Site Location Map B-26

27 LEGEND B-1 P-1 Approximate Location of Soil Boring Approximate Location of Soil Boring/Percolation Test B-1 P-1 Proposed 5-Story Residential Wrap Building with 7-Level Parking Garage Proposed 5-Level Parking Garage Greenlaw Partners 3800 Chapman Avenue City of Orange Orange County, California GeoTek Figure 2 Boring Location Map B-27