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PD 16-14; OZAKI PARCEL 2; GEOTECHNICAL EVALUATION FOR PROPOSED CONSTRUCTION AT 1645 CHESTNUT AVE; 2016-02-22
W.O. 7014-A-SC FEBRUARY 22, 2016 GEOTECHNICAL EVALUATION FOR PROPOSED CONSTRUCTION AT 1645 CHESTNUT AVENUE CARLSBAD1WDIEGO COUCALIEORiA'92008 19 0. 1'H;k RECE WED OCT 20 2016 LAND DEVELOPMENT ENGINEERING Geotechnical. Geologic. Coastal • Environmental 5741 Palmer Way • Carlsbad, California 92010 • (760) 438-3155 • FAX (760) 931-0915 • www.geosoilsinc.com February 22, 2016 W.O. 7014-A-SC Mr. Ron Ozaki 155 7th Street Del Mar, California 92014 Subject: Geotechnical Evaluation for Proposed Construction at 1645 Chestnut Avenue, Carlsbad, San Diego County, California Dear Mr. Ozaki: In accordance with your request and authorization, GeoSoils, Inc. (GSI) is pleased to present the results of our preliminary geotechnical evaluation at the subject site. The purpose of our study was to evaluate the geologic and geotechnical conditions at the site, in order to develop preliminary recommendations for site earthwork and the design of foundations, walls, and pavements related to the proposed residential construction at the property. EXECUTIVE SUMMARY Based upon our field exploration, geologic, and geotechnical engineering analysis, the proposed development appears feasible from a soils engineering and geologic viewpoint, provided that the recommendations presented in the text of this report are properly incorporated into the design and construction of the project. The most significant elements of our study are summarized below: In general, the site may be characterized as a existing, developed site, underlain colluvial soils developed on Quaternary-age, older paralic deposits. Due to their relatively low density and lack of uniformity, all surficial deposits of colluvium, and near surface, weathered older paralic deposits (if present) are considered unsuitable for the support of settlement-sensitive improvements (i.e., residential foundations, concrete slab-on-grade floors, site walls, exterior hardscape, etc.) and/or engineered fill in their existing state. Based on the available data, the thickness of these soils across the site is anticipated to vary between approximately 1½ to 3 feet. However, localized thicker sections of unsuitable soils cannot be precluded, and should be anticipated. Conversely, the underlying unweathered older paralic deposits are generally considered suitable for the support of settlement-sensitive improvements and/or engineered fill. It should be noted that the 2013 California Building Code ([2013 CBC], California Building Standards Commission [CBSC], 2013) indicates that removals of unsuitable soils be performed across all areas to be graded, under the purview of the grading permit, not just within the influence of the residential structure. Relatively deep removals may also necessitate a special zone of consideration, on perimeter/confining areas. This zone would be approximately equal to the depth of removals, if removals cannot be performed onsite or offsite. Thus, any settlement-sensitive improvements (walls, curbs, flatwork, etc.), constructed within this zone may require deepened foundations, reinforcement, etc., or will retain some potential for settlement and associated distress. This will also require proper disclosure to any owners and all interested/affected parties should this condition exist at the conclusion of grading. Expansion Index (E.l.), and Plasticity Index (P.1.) testing performed on a representative sample of the onsite soil indicates an E.I. of less than 20 (very low expansive), and non plastic soil conditions. As such, site soils are considered non-detrimentally expansive and no specific foundation design appears necessary to mitigate expansive soil effects, on a preliminary basis. Soil expansion should be re-evaluated at the conclusion of grading. Laboratory testing indicates that site soils are relatively neutral with respect to pH, mildly corrosive to exposed buried metals when saturated, present negligible sulfate exposure to concrete and are below the action level for chloride exposure. Site soils are classified as "Exposure Class Cl." Corrosion testing at the completion of grading is recommended in order to obtain actual corrosion data specific to design grades. Neither a regional groundwater table nor perched water was encountered during our subsurface studies to the depth explored. As such, regional groundwater is not anticipated to significantly affect the planned improvements. Perched water may occur in the future along zones of contrasting permeability and/or density. This potential should be disclosed to all interested/affected parties. Our evaluation indicates there are no known active faults crossing the site and the natural slope upon which the site is located has very low susceptibility to deep-seated landslides. Owing to the depth to groundwater and the dense nature of the terrace (paralic) deposits, the potential for the site to be adversely affected by liquefaction is considered very low. Site soils are considered erosive. Thus, properly designed site drainage is necessary in reducing erosion damage to the planned improvements. The seismic acceleration values and design parameters provided herein should be considered during the design of the proposed development. The adverse effects of seismic shaking on the structure(s) will likely be wall cracks, some foundation/slab distress, and some seismic settlement. However, it is anticipated that the structure will be repairable in the event of the design seismic event. This potential should be disclosed to any owners and all interested/affected parties. Ron Ozaki W.O. 7014-A-SC FiIe:e:\wpl2\7000\7014a.pge GeOSOlIS, Inc. Page Two Additional adverse geologic features that would preclude project feasibility were not encountered, based on the available data. The recommendations presented in this report should be incorporated into the design and construction considerations 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 subm GeoSoils, Inc. No.1934 Z Certlfled J 4t C4 \ Engineering / 4~G so Robert G. Crisman OF C410 Engineering Geologist, CEG 1934 RGC/JPF/DWS/jh Distribution: (3) Addressee (9! No. RCE 47857 \L.3I/*j Civil Engineer, R E 47857 Ron Ozaki W.O. 7014-A-SC File:e:\wp12\7000\7014a.pge GeoSoM4 Inc. Page Three TABLE OF CONTENTS SCOPE OF SERVICES . 1 SITE DESCRIPTION AND PROPOSED DEVELOPMENT .........................1 FIELD STUDIES .........................................................3 REGIONAL GEOLOGY ...................................................3 SITE GEOLOGIC UNITS ..................................................5 General..........................................................5 Colluvium (Not Mapped) .......................................5 Quaternary Older Paralic Deposits (Map Symbol - Qop2-4) ...........5 Structural Geology .................................................5 GROUNDWATER ........................................................5 GEOLOGIC HAZARDS EVALUATION ........................................6 Mass Wasting/Landslide Susceptibility .................................6 FAULTING AND REGIONAL SEISMICITY .....................................6 Regional Faults ....................................................6 Local Faulting .....................................................6 Seismicity........................................................7 Seismic Shaking Parameters .........................................7 SECONDARY SEISMIC HAZARDS ..........................................9 SLOPE STABILITY .......................................................9 LABORATORY TESTING ...................................................9 Classification ......................................................9 Expansion Index ...................................................9 Particle-Size Analysis ..............................................10 Saturated Resistivity, pH, and Soluble Sulfates, and Chlorides .............10 Corrosion Summary .........................................10 PRELIMINARY CONCLUSIONS AND RECOMMENDATIONS ....................10 EARTHWORK CONSTRUCTION RECOMMENDATIONS .......................13 General.........................................................13 Demolition/Grubbing ..............................................13 Treatment of Existing Ground .......................................14 Fill Suitability .....................................................14 Fill Placement ....................................................14 GeoSoils, Inc. Graded Slopes . 15 Temporary Slopes ................................................15 PRELIMINARY RECOMMENDATIONS - FOUNDATIONS .......................15 General.........................................................15 Preliminary Foundation Design ......................................16 PRELIMINARY FOUNDATION CONSTRUCTION RECOMMENDATIONS ...........16 Foundation Settlement .............................................18 SOIL MOISTURE TRANSMISSION CONSIDERATIONS ........................18 WALL DESIGN PARAMETERS ............................................20 General.........................................................20 Conventional Retaining Walls .......................................20 Preliminary Retaining Wall Foundation Design ....................20 Restrained Walls ............................................21 Cantilevered Walls ...........................................21 Seismic Surcharge ................................................22 Retaining Wall Backfill and Drainage ..................................23 Wall/Retaining Wall Footing Transitions ...............................27 DRIVEWAY/PARKING, FLATWORK, AND OTHER IMPROVEMENTS ..............27 DEVELOPMENT CRITERIA ...............................................29 Onsite Storm Water Treatment ......................................29 Slope Maintenance and Planting .....................................30 Drainage........................................................31 Erosion Control ...................................................31 Landscape Maintenance ...........................................31 Gutters and Downspouts ...........................................32 Subsurface and Surface Water ......................................32 Site Improvements ................................................32 TileFlooring .....................................................33 Additional Grading ................................................33 Footing Trench Excavation .........................................33 Trenching/Temporary Construction Backcuts ..........................33 Utility Trench Backfill ..............................................34 SUMMARY OF RECOMMENDATIONS REGARDING GEOTECHNICAL OBSERVATION AND TESTING........................................................34 OTHER DESIGN PROFESSIONALS/CONSULTANTS ..........................35 PLAN REVIEW .........................................................36 Ron Ozaki Table of Contents Fi1e:e:\wp12\7000\7014a.pge GeoSoils, Inc. Page ii LIMITATIONS . 36 FIGURES: Figure 1 - Site Location Map .........................................2 Figure 2- Geotechnical Map .........................................4 Detail 1 - Typical Retaining Wall Backfill and Drainage Detail ..............24 Detail 2 - Retaining Wall Backfill and Subdrain Detail Geotextile Drain .......25 Detail 3 - Retaining Wall and Subdrain Detail Clean Sand Backfill ...........26 ATTACHMENTS: Appendix A - References ...................................Rear of Text Appendix B - Hand Auger Boring Logs ........................Rear of Text Appendix C - Seismicity ....................................Rear of Text Appendix D - General Earthwork and Grading Guidelines .........Rear of Text Ron Ozaki Table of Content File:e:\wpl2\7000\7014a.pge i s Page ii GEOTECHNICAL EVALUATION FOR PROPOSED CONSTRUCTION AT 1645 CHESTNUT AVENUE CARLSBAD, SAN DIEGO COUNTY, CALIFORNIA 92067 SCOPE OF SERVICES The scope of our services has included the following: Review of readily available published literature, aerial photographs, and maps of the vicinity (see Appendix A), including proprietary in-house geologic/geotechnical reports for other nearby sites. Site reconnaissance mapping and the excavation of three (3) exploratory hand- auger borings to evaluate the soil/formation profiles, sample representative earth materials, and delineate the horizontal and vertical extent of earth material units (see Appendix B). General areal seismicity evaluation (see Appendix C). Appropriate laboratory testing of relatively undisturbed and representative bulk soil samples collected during our geologic mapping and subsurface exploration program. Analysis of field and laboratory data relative to the proposed development. Appropriate engineering and geologic analyses of data collected, and the preparation of this summary report and accompaniments. SITE DESCRIPTION AND PROPOSED DEVELOPMENT The subject site consists of a relatively flat-lying, "flag" lot property in the City of Carlsbad, San Diego County, California (see Site Location Map, Figure 1). The property is bounded by residential property and Chestnut Avenue to the northwest, and existing residential property on the remaining sides. Access to subject property is via an existing easement from Chestnut Avenue to the property located south of an existing residential lot fronting Chestnut Avenue. Existing improvements to the property consist of a small storage structure. The site appears to be at an approximate elevation of 166 feet above Mean Sea Level (MSL). Drainage appears to be generally directed offsite to the south, toward the back (south) of the property. Vegetation onsite consists of scattered trees, and other typical residential landscaping. It is anticipated that the existing storage structure is to be removed, and the site will be prepared for the construction of a single family residential structure. The proposed development is not currently known (single or double story/detached garage, etc.). GeoSoils, Inc. z: > SflE .4 0 Ic- AVIC SITE '.5 Mt KeW 1, 6 • \\ ;day Chase ,. \ \ Jr IPA st \A If- - .7 7 \ ," '. %Sch '' 0 1000 2000 3000 4000 ,l6 se :. Base Map: TOPOR ©2003 National Geographic, U.S.G.S. San Luis Rey Quadrangle, California -- San Diego Co., 7.5 Minute, dated 1997, current, 1999. LQe 0, Dt@ qO 01 /1 I . 2 Vn Sa* t < \ NOT TO SCALE Base Map: Google Maps, Copyright 2016 Google, Map Data Copyright 2016 Google This map is copyrighted by Google 2016. It is unlawful to copy or reproduce all or any part thereof, whether for personal use or resale, without permission. All rights reserved. W.O. de -A-SC 7014 4 SITE LOCATION MAP N Figure 1 However, GSI anticipates that the construction would consist of wood frames with typical foundations and slab-on-grade ground floors. Building loads are assumed to be typical for this type of relatively light construction. Sewage disposal is anticipated to be connected into the regional, municipal system. Storm water may be treated onsite prior to its delivery into the municipal system. FIELD STUDIES Site-specific field studies were conducted by GSI during January 2016, and consisted of reconnaissance geologic mapping and the excavation of three (3) exploratory test borings with a hand auger, for an evaluation of near-surface soil and geologic conditions onsite. The test borings were logged by a representative of this office who collected representative bulk and undisturbed soil samples for appropriate laboratory testing. The logs of the hand -auger borings are presented in Appendix B. The approximate location of the hand-auger borings are presented on the Geotechnical Map (see Figure 2). REGIONAL GEOLOGY The subject property lies within the coastal plain physiographic region of the Peninsular Ranges Geomorphic Province of southern California. This region consists of dissected, mesa-like terraces that transition inland to rolling hills. The encompassing Peninsular Ranges Geomorphic Province is characterized as elongated mountain ranges and valleys that trend northwesterly. This geomorphic province extends from the base of the east-west aligned Santa Monica - San Gabriel Mountains, and continues south into Baja California. The mountain ranges within this province are underlain by basement rocks consisting of pre-Cretaceous metasedimentary rocks, Jurassic metavolcanic rocks, and Cretaceous plutonic (granitic) rocks. In the Southern California region, deposition occurred during the Cretaceous Period and Cenozoic Era in the continental margin of a forearc basin. Sediments, derived from Cretaceous-age plutonic rocks and Jurassic-age volcanic rocks, were deposited during the Tertiary Period (Eocene-age) into the narrow, steep, coastal plain and continental margin of the basin. These rocks have been uplifted, eroded, and deeply incised. During early Pleistocene time, a broad coastal plain was developed from the deposition of marine terrace deposits. During mid to late Pleistocene time, this plain was uplifted, eroded and incised. Alluvial deposits have since filled the lower valleys, and young marine sediments are currently being deposited/eroded within coastal and beach areas. Regional geologic mapping by Kennedy and Tan (2007) indicate the site is underlain by Quaternary-age older paralic deposits (formally known as "terrace deposits"), which is considered bedrock, or formational sediments, at the site. Based on our experience in the vicinity, older deposits of Eocene-age sedimentary bedrock likely underlie the site at depth. Ron Ozaki W.O. 7014-A-SC 1645 Chestnut Avenue, Carlsbad February 22, 2016 File:e:\wp12\7000\7014a.pge GeOSOdS, Inc. Page 3 2 : _ 1 r • , ,. r1 - 1 L I 1•• - ___ ------ I S . Fl t S X-1-APPROXIMATE LOCATION OF HA-3 STUDY AREA/PROPERTY LINE Qop ® * * HA -2 t p HA-1 ..11% 41 Jl4c'_ GRAPHIC SCALE 50 0 25 5 / ALL LOCATIONS ARE APPROXIMATE This document or efile is not a part of the Construction Documents and should not be relied upon as being an 1" = 50' accurate depiction of design. GeoSoUi,Jnç. GS! LEGEND HA-3 .1 - APPROXIMATE LOCATION OF GEO TECHNICAL MAP HAND-AUGER BORING QOP - QUA TERNARY OLD PARALIC DEPOSITS Figure 2 2-4 WO. 7014-A-SC DATE; 02116 SCALE: I"=50' SITE GEOLOGIC UNITS General The earth material units that were observed and/or encountered at the subject site consist of surficial deposits of undifferentiated colluvium, overlying Quaternary-age older paralic deposits at shallow depth. A general description of each material type is presented as follows, from youngest to oldest. Colluvium (Not Mapped) As observed, colluvium (topsoil) occurs at the surface and consists of dark brown, moist, loose, and porous silty sand. Where encountered in our borings, the thickness of these earth materials was on the order of 1 1/2 to 3 feet thick. All colluvium is considered prone to settlement under loading and therefore should be removed and reused as properly engineered fill, in areas proposed for settlements-sensitive improvements. Quaternary Older Paralic Deposits (Map Symbol - 00p2-4) Quaternary-age older paralic deposits (terrace deposits) were observed underlying existing colluvium at depths on the order of 11/2 to 3 feet below existing grades onsite. Where encountered, these sediments generally consisted of moist, medium dense, yellowish brown, silty sand. These deposits are considered to be suitable bearing materials for the support of new fills, or settlement-sensitive improvements. Structural Geology Bedding within older paralic deposits is generally flat lying to very gently dipping and should not affect site development. GROUNDWATER GSI did not observe evidence of a regional groundwater table nor perched water within our subsurface explorations. Regional groundwater is estimated to be generally within a few feet of sea level, and is not anticipated to significantly affect proposed site development, provided that the recommendations contained in this report are properly incorporated into final design and construction. These observations reflect site conditions at the time of our investigation and do not preclude future changes in local groundwater conditions from excessive irrigation, precipitation, or that were not obvious, at the time of our investigation. Seeps, springs, or other indications of subsurface water were not noted on the subject property during the time of our field investigation. However, perched water seepage may occur locally (as the result of heavy precipitation and/or irrigation, or damaged wet utilities) along zones of contrasting permeabilities/densities (colluvium/paralic deposit contacts, Ron Ozaki W.O. 7014-A-SC 1645 Chestnut Avenue, Carlsbad February 22, 2016 File:e:\wp12\7000\7014a.pge Geoftilsq Inc. Page 5 sandy/clayey fill lifts, etc.) or along geologic discontinuities. This potential should be anticipated and disclosed to all interested/affected parties. Due to the potential for post-development perched water to manifest near the surface, owing to as-graded permeability/density contrasts, more onerous slab design is necessary for any new slab-on-grade floor (State of California, 2016). Recommendations for reducing the amount of water and/or water vapor through slab-on-grade floors are provided in the "Soil. Moisture Considerations" sections of this report. GEOLOGIC HAZARDS EVALUATION Mass Wasting/Landslide Susceptibility Due to the relatively flat lying condition of the site, and the nature of the underlying soils, the site is not considered susceptible to significant mass wasting or landsliding. The onsite soils are, however, considered erosive. Therefore, slopes comprised of these materials may be subject to ruling, gullying, sloughing, and surficial slope failures depending on rainfall severity and surface drainage. However, such risks can be minimized through properly designed and controlled surface drainage. FAULTING AND REGIONAL SEISMICITY Regional Faults Our review indicates that there are no known active faults crossing the project and the site is not within an Alquist-Priolo Earthquake Fault Zone (Bryant and Hart, 2007). However, the site is situated in an area of active faulting. The Rose Canyon fault is closest known active fault to the site (located at a distance of approximately 5.8 miles [9.3 kilometers]) and should have the greatest effect on the site in the form of strong ground shaking, should the design earthquake occur. A list and the location of the Rose Canyon fault and other major faults relative to the site is provided in Appendix C. The possibility of ground acceleration, or shaking at the site, may be considered as approximately similar to the southern California region as a whole. Local Faulting Although active faults lie within a few miles of the site, no local active faulting was noted in our review, nor observed to specifically transect the site during the field investigation. Additionally, a review of available regional geologic maps does not indicate the presence of local active faults crossing the specific project site. Ron Ozaki W.O. 7014-A-SC 1645 Chestnut Avenue, Carlsbad February 22, 2016 FiIe:e:\wpl2\7000\7014a.pge GeoSods, Inc. Page 6 Seismicity It is our understanding that site-specific seismic design criteria from the 2013 California Building Code ([2013 CBC], California Building Standards Commission [CBSC], 2013), are to be utilized for foundation design. Much of the 2013 CBC relies on the American Society of Civil Engineers (ASCE) Minimum Design Loads for Buildings and Other Structures (ASCE Standard 7-10). The seismic design parameters provided herein are based on the 2013 CBC. The acceleration-attenuation relation of Bozorgnia, Campbell, and Niazi (1999) has been incorporated into EQFAULT (Blake, 2000a). EQFAULT is a computer program developed by Thomas F. Blake (2000a), which performs deterministic seismic hazard analyses using digitized California faults as earthquake sources. The program estimates the closest distance between each fault and a given site. If a fault is found to be within a user-selected radius, the program estimates peak horizontal ground acceleration that may occur at the site from an upper bound (formerly "maximum credible earthquake"), on that fault. Upper bound refers to the maximum expected ground acceleration produced from a given fault. Site acceleration (g) was computed by one user-selected acceleration-attenuation relation that is contained in EQFAULT. Based on the EQFAULT program, a peak horizontal ground acceleration from an upper bound event on the Rose Canyon fault may be on the order of 0.53 g. The computer printouts of pertinent portions of the EQFAULT program are included within Appendix C. Historical site seismicity was evaluated with the acceleration-attenuation relation of Bozorgnia, Campbell, and Niazi (1999), and the computer program EQSEARCH (Blake, 2000b, updated to June 2013). This program performs a search of the historical earthquake records for magnitude 5.0 to 9.0 seismic events within a 100-kilometer radius, between the years 1800 through January 2016. Based on the selected acceleration-attenuation relationship, a peak horizontal ground acceleration is estimated, which may have affected the site during the specific event listed. Based on the available data and the attenuation relationship used, the estimated maximum (peak) site acceleration during the period 1800 through January 2016 was about 0.24 g. A historic earthquake epicenter map and a seismic recurrence curve are also estimated/generated from the historical data. Computer printouts of the EQSEARCH program are presented in Appendix C. Seismic Shaking Parameters Based on the site conditions, the following table summarizes the updated site-specific design criteria obtained from the 2013 CBC (CBSC, 2013), Chapter 16 Structural Design, Section 1613, Earthquake Loads. The computer program "U.S. Seismic Design Maps, provided by the United States Geologic Survey (USGS, 2014) was utilized for design (http://geohazards.usgs.gov/designmaps/us/application.php). The short spectral response utilizes a period of 0.2 seconds. Ron Ozaki W.O. 7014-A-SC 1645 Chestnut Avenue, Carlsbad February 22, 2016 Fi1e:e:\wp12\7000\7014a.pge GeOSOUS9 Inc. Page 7 2013 CBC SEISMIC DESIGN PARAMETERS PARAMETER VALUE 2013 CBC REFERENCE Risk Category I, II, or Ill Table 1604.5 Site Class D Section 1613.3.2/ASCE 7-10 (p. 203-205) Spectral Response -(0.2 sec), S9 1.125g Section 1613.3.1 Figure 1613.3.1 (1) Spectral Response - (1 sec), S1 0.4329 Section 1613.3.1 Figure 1613.3.1 (2) Site Coefficient, F. 1.050 Table 1613.3.3(1) Site Coefficient, F 1.568 Table 1613.3.3(2) Maximum Considered Earthquake Spectral 1.1819 Section 1613.3.3 Response Acceleration (0.2 sec), SM$ (Eqn 16-37) Maximum Considered Earthquake Spectral 0.677g Section 1613.3.3 Response Acceleration (1 sec), S,, (Eqn 16-38) 5% Damped Design Spectral Response 0.7879 Section 1613.3.4 Acceleration (0.2 sec), S (Eqn 16-39) 5% Damped Design Spectral Response 0.452g Section 1613.3.4 Acceleration (1 sec), S01 (Eqn 16-40) PGA, (Probabilistic Vertical Ground Acceleration may be 0.4679 ASCE 7-10 (Eqn 11.8. 1) assumed as about 50% of this value) Seismic Design Category'3 D Section 1613.3.5/ASCE 7-10 (Table 11.6-1 or 11.6-2) GENERAL SEISMIC PARAMETERS PARAMETER I VALUE Distance to Seismic Source (Rose Canyon) 5.8 mi (9.3 km)'" Upper Bound Earthquake (Rose Canyon fault) M = 7.2(21 '"- From Blake (2000a) (2) - Cao, et al. (2003) Conformance to the criteria above for seismic design does not constitute any kind of guarantee or assurance that significant structural damage or ground failure will not occur in the event of a large earthquake. The primary goal of seismic design is to protect life, not to eliminate all damage, since such design may be economically prohibitive. Cumulative effects of seismic events are not addressed in the 2013 CBC (CBSC, 2013) and regular maintenance and repair following locally significant seismic events (i.e., M5.5) will likely be necessary, as is the case in all of southern California. Ron Ozaki W.O. 7014-A-SC 1645 Chestnut Avenue, Carlsbad February 22, 2016 Fi1e:e:\wp12\7000\7014a.pge GeOSO11S Inc. Page 8 SECONDARY SEISMIC HAZARDS The following list includes other geologic/seismic related hazards that have been considered during our evaluation of the site. The hazards listed are considered negligible and/or mitigated as a result of site location, soil characteristics, and typical site development procedures: Liquefaction Lateral Spreading Subsidence Ground Lurching or Shallow Ground Rupture Tsunami Seiche SLOPE STABILITY Based on site conditions and planned improvements, significant cut and/or fill slopes are not anticipated. Therefore, no recommendations are deemed necessary. Temporary slopes for construction (i.e., trenching, etc.) are discussed in subsequent sections of our report. LABORATORY TESTING Laboratory tests were performed on representative samples of site earth materials collected during our subsurface exploration in order to evaluate their physical characteristics. Test procedures used and results obtained are presented below. Classification Soils were visually classified with respect to the Unified Soil Classification System (U.S.C.S.) in general accordance with ASTM D 2487 and D 2488. The soil classifications of the onsite soils are provided on the Hand-Auger Logs in Appendix B. Expansion Index Tests were performed on a representative soil sample obtained from Hand-Auger HA-1 (composite sample) to evaluate expansion potential. Testing was performed in general accordance with ASTM D 4829, and indicates a very low expansion potential (Expansion Index [E.l.] = <5), where tested. Ron Ozaki W.O. 7014-A-SC 1645 Chestnut Avenue, Carlsbad February 22, 2016 F1le:e:\wp12\7000\7014a.pge Ge"oiis, Inc. Page 9 Particle-Size Analysis A particle-size evaluation was performed on a representative, soil sample obtained from Hand-Auger HA-1 (composite sample) in general accordance with ASTM D 422-63. The testing was utilized to evaluate the soil classification in accordance with the Unified Soil Classification System (USCS). The results of the particle-size evaluation indicate that the tested soil is a silty sand (SM). Results = 0.0% gravel, 76.2% sand, 23.8% silt/clay. Saturated Resistivity, pH, and Soluble Sulfates, and Chlorides GSI conducted sampling of onsite earth materials for general soil corrosivity and soluble sulfates, and chlorides testing. The testing (performed by an outside laboratory) included evaluation of soil pH, soluble sulfates, chlorides, and saturated resistivity. Test results are presented in the following table: SATURATED SOLUBLE SOLUBLE SAMPLE LOCATION pH RESISTIVITY SULFATES CHLORIDES AND DEPTH (FT) (ohm-cm) (PPM) (ppm) HA-1 @ 0-3 7.35 3,800 0.0135 62 Corrosion Summary Laboratory testing indicates that tested samples of the onsite soils are relatively neutral with respect to soil acidity/alkalinity, are mildly corrosive to exposed, buried metals when saturated, present negligible ("not applicable" per ACI 318-11) sulfate exposure to concrete, and although some what elevated, are below the action level for chloride exposure (per State of California Department of Transportation, 2003). Reinforced concrete mix design for foundations, slab-on-grade floors, and pavements should minimally conform to "Exposure Class Cl" in Table 4.2.1 of ACI 318-11, as concrete would likely be exposed to moisture. It should be noted that GSI does not consult in the field of corrosion engineering. The client and project architect should agree on the level of corrosion protection required for the project and seek consultation from a qualified corrosion consultant as warranted. PRELIMINARY CONCLUSIONS AND RECOMMENDATIONS Based on our field exploration, laboratory testing, and geotechnical engineering analysis, it is our opinion that the subject site is suitable for the proposed residential development from a geotechnical engineering and geologic viewpoint, provided that the recommendations presented in the following sections are incorporated into the design and Ron Ozaki W.O. 7014-A-SC 1645 Chestnut Avenue, Carlsbad February 22, 2016 F11e:e:\wp12\7000\7014a.p9e Geosoilsq Inc. Page 10 construction phases of site development. The primary geotechnical concerns with respect to the proposed development and improvements are: Earth materials characteristics and depth to competent bearing material. On-going expansion and corrosion potential of site soils. Erosiveness of site earth materials. Potential for perched water during and following site development. Temporary slope stability. Regional seismic activity. The recommendations presented herein consider these as well as other aspects of the site. The engineering analyses performed concerning site preparation and the recommendations presented herein have been completed using the information provided and obtained during our field work. In the event that any significant changes are made to proposed site development, the conclusions and recommendations contained in this report shall not be considered valid unless the changes are reviewed and the recommendations of this report verified or modified in writing by this office. Foundation design parameters are considered preliminary until the foundation design, layout, and structural loads are provided to this office for review. Soil engineering, observation, and testing services should be provided during grading to aid the contractor in removing unsuitable soils and in his effort to compact the fill. Geologic observations should be performed during any grading and foundation construction to verify and/or further evaluate geologic conditions. Although unlikely, if adverse geologic structures are encountered, supplemental recommendations and earthwork may be warranted. Surflcial soils within approximately 1 1/2 to 3 feet from surface grades are considered unsuitable for the support of the planned settlement-sensitive improvements (i.e., residential structure, walls, concrete slab-on-grade floors, and exterior pavements, etc.) or new planned fills. Unsuitable soils within the influence of planned settlement-sensitive improvements and/or planned fill should be removed to expose suitable older paralic deposits and then be reused as properly engineered fill. In order to provide for the uniform support of the structure, a minimum 3-foot thick later of compacted fill is recommended for the support of structure (s). Based on the recommended removal depths, it may be necessary to undercut the building pad areas in order to achieve the desired minimum fill thickness. Undercutting should be completed for a minimum lateral distance of at least 5 feet beyond the building footprint. Ron Ozaki W.O. 7014-A-SC 1645 Chestnut Avenue Carlsbad February 22 2016 FiIe:e:\wp12\70007014a.pge GeoSods, Inc. Page 11 Testing performed on a representative sample of the onsite soils indicates very low expansive soil conditions. On a preliminary basis, specific foundation design to resist expansive soil effects is not necessary. However, GSl suggests that the soil moisture within the underlying subgrade is near, or above optimum moisture content prior to the placement of the underlayment sand and vapor retarder. Laboratory testing indicates that site soils are relatively neutral (pH), and mildly corrosive to exposed buried metals when saturated. Testing also indicates that site soils present negligible ("not applicable" per ACI 318-11) sulfate exposure to concrete and are below the action level for chloride exposure. Site soils are classified as "Exposure Class Cl." The client and project architect should agree on the level of corrosion protection required for the project and seek consultation from a qualified corrosion consultant as warranted. Additional testing at the completion of remedial grading is recommended in order to verify these assumptions. Site soils are considered erosive. Surface drainage should be designed to eliminate the potential for concentrated flows. Positive surface drainage away from foundations and tops of slopes is recommended. Temporary erosion control measures should be implemented until vegetative covering is well established. The homeowner will need to maintain proper surface drainage over the life of the project. No evidence of a high regional groundwater table nor perched water was observed during our subsurface exploration within the property. However, due to the nature of site earth materials, there is a potential for perched water to occur both during and following site development. This potential should be disclosed to all interested/affected parties. Should perched water conditions be encountered, this office could provide recommendations for mitigation. Typical mitigation includes subdrainage system, cut-off barriers, etc. On a preliminary basis, temporary slopes should be constructed in accordance with CAL-OSHA guidelines for Type "B" soils. All temporary slopes should be evaluated by the geotechnical consultant, prior to worker entry. Should adverse conditions be identified, the slope may need to be laid back to a flatter gradient or require the use of shoring. The seismicity-acceleration values provided herein should be considered during the design and construction of the proposed development. General Earthwork and Grading Guidelines are provided at the end of this report as Appendix D. Specific recommendations are provided below. Ron Ozaki W.O. 7014-A-SC 1645 Chestnut Avenue, Carlsbad February 22, 2016 File:e:\wpl2\7000\7014a.pge GCOSOiIS Inc. Page 12 EARTHWORK CONSTRUCTION RECOMMENDATIONS General All earthwork should conform to the guidelines presented in the 2013 CBC (CBSC, 2013), the requirements of the City of Carlsbad, and the General Earthwork and Grading Guidelines presented in Appendix 0, except where specifically superceded in the text of this report. Prior to earthwork, a GSI representative should be present at the preconstruction meeting to provide additional earthwork guidelines, if needed, and review the earthwork schedule. This office should be notified in advance of any fill placement, supplemental regrading of the site, or backfilling underground utilitytrenches and retaining walls after rough earthwork has been completed. This includes grading for driveway approaches, driveways, and exterior hardscape. During earthwork construction, all site preparation and the general grading procedures of the contractor should be observed and the fill selectively tested by a representative (s) of GSI. If unusual or unexpected conditions are exposed in the field, they should be reviewed by this office and, if warranted, modified and/or additional recommendations will be offered. All applicable requirements of local and national construction and general industry safety orders, the Occupational Safety and Health Act (OSHA), and the Construction Safety Act should be met. It is the onsite general contractor and individual subcontractors responsibility to provide a save working environment for our field staff who are onsite. GSI does not consult in the area of safety engineering. Demolition/Grubbing Vegetation and any miscellaneous debris should be removed from the areas of proposed grading. Any existing subsurface structures uncovered during the recommended removal should be observed by GSI so that appropriate remedial recommendations can be provided. Cavities or loose soils remaining after demolition and site clearance should be cleaned out and observed by the soil engineer. The cavities should be replaced with fill materials that have been moisture conditioned to at least optimum moisture content and compacted to at least 90 percent of the laboratory standard. Onsite septic systems (if encountered) should be removed in accordance with San Diego County Department of Environmental Health standards/guidelines. Ron Ozaki W.O. 7014-A-SC 1645 Chestnut Avenue, Carlsbad February 22, 2016 FlIe:e:\wpl2\7000\7014a.pge GeoSoils, Inc. Page 13 Treatment of ExistinQ Ground Removals should consist of all surficial deposits of fill, colluvium, and weathered paralic deposits. Based on our site work, removals depths on the order of 2 to 21/2 feet should be anticipated. These soils may be re-used as fill, provided that the soil is cleaned of any deleterious material and moisture conditioned, and compacted to a minimum 90 percent relative compaction per ASTM D 1557. Removals should be completed throughout the entire building area. In addition to removals within the building envelopes, overexcavation/undercutting of the underlying formational soil should be performed in order to provide for at least 3 feet of compacted fill below finish grade. Undercutting should be completed for a minimum lateral distance of at least 5 feet beyond the building footprint. Once removals and overexcavation is completed, the fill should be cleaned of deleterious materials, moisture conditioned, and recompacted to at least 90 percent relative compaction per ASTM D 1557. Subsequent to the above removals/overexcavation, the exposed bottom should be scarified to a depth of at least 6 to 8 inches, brought to at least optimum moisture content, and recompacted to a minimum relative compaction of 90 percent of the laboratory standard, prior to any fill placement. Existing fill and removed natural ground materials may be reused as compacted fill provided that major concentrations of vegetation and miscellaneous debris are removed from the site, prior to or during fill placement. Localized deeper removals may be necessary due to buried drainage channel meanders or dry porous materials, septic systems, etc. The project soils engineer/geologist should observe all removal areas during the grading. Fill Suitability Existing earth materials onsite should generate relatively fine grained, granular fill material, and oversize material (i.e., greater than 12 inches in long dimension) is not anticipated. If soil importation is planned, samples of the soil import should be evaluated by this office prior to importing in order to assure compatibility with the onsite site soils and the recommendations presented in this report. Import soils, if used, should be relatively sandy and very low expansive (i.e., E.I. less than 20). Fill Placement Subsequent to ground preparation, fill materials should be brought to at least optimum moisture content, placed in thin 6- to 8-inch lifts, and mechanically compacted to obtain a minimum relative compaction of 90 percent of the laboratory standard. Ron Ozaki W.O. 7014-A-SC 1645 Chestnut Avenue, Carlsbad February 22, 2016 File:e:\wpl2\7000\7014a.pge oSoiIs, Inc. Page 14 Fill materials should be cleansed of major vegetation and debris prior to placement. Any import materials should be observed and deemed suitable by the soils engineer prior to placement on the site. Foundation designs may be altered if import materials have a greater expansion value than the onsite materials encountered in this investigation. Graded Slopes Significant graded slope are not planned, nor anticipated for this project. Temporary Slopes Temporary slopes for excavations greater than 4 feet, but less than 20 feet in overall height should conform to CAL-OSHA and/or OSHA requirements for Type "B" soils. Temporary slopes, up to a maximum height of ±20 feet, may be excavated at a 1:1 (h:v) gradient, or flatter, provided groundwater and/or running sands are not exposed. Construction materials or soil stockpiles should not be placed within 'H' of any temporary slope where 'H' equals the height of the temporary slope. All temporary slopes should be observed by a licensed engineering geologist and/or geotechnical engineer prior to worker entry into the excavation. PRELIMINARY RECOMMENDATIONS -FOUNDATIONS General Preliminary recommendations for foundation design and construction are provided in the following sections. These preliminary recommendations have been developed from our understanding of the currently planned site development, site observations, subsurface exploration, laboratory testing, and engineering analyses. Foundation design should be re-evaluated at the conclusion of site grading/remedial earthwork for the as-graded soil conditions. Although not anticipated, revisions to these recommendations may be necessary. In the event that the information concerning the proposed development plan is not correct, or any changes in the design, location or loading conditions of the proposed additions are made, the conclusions and recommendations contained in this report shall not be considered valid unless the changes are reviewed and conclusions of this report are modified or approved in writing by this office. The information and recommendations presented in this section are not meant to supercede design by the project structural engineer or civil engineer specializing in structural design. Upon request, GSI could provide additional input/consultation regarding soil parameters, as related to foundation design. Ron Ozaki W.O. 7014-A-SC 1645 Chestnut Avenue, Carlsbad February 22, 2016 File:e:\wpl2\7000\7014a.pge Geoftilsh Inc. Page 15 Preliminary Foundation Design The foundation systems should be designed and constructed in accordance with guidelines presented in the 2013 CBC. An allowable bearing value of 2,000 pounds per square foot (psf) may be used for the design of footings that maintain a minimum width of 12 inches and a minimum depth of 12 inches (below the lowest adjacent grade) and are founded entirely into properly compacted, engineered fill. This value may be increased by 20 percent for each additional 12 inches in footing depth to a maximum value of 2,500 psf. These values may be increased by one-third when considering short duration seismic or wind loads. Isolated pad footings should have a minimum dimension of at least 24 inches square and a minimum embedment of 24 inches below the lowest adjacent grade into properly engineered fill. Foundation embedment depth excludes concrete slabs-on-grade, and/or slab underlayment. Foundations should not simultaneously bear on unweathered paralic deposits and engineered fill. For foundations deriving passive resistance from engineered fill, a passive earth pressure may be computed as an equivalent fluid having a density of 250 pcf, with a maximum earth pressure of 2,500 psf. The upper 6 inches of passive pressure should be neglected if not confined by slabs or pavement. For lateral sliding resistance, a 0.35 coefficient of friction may be utilized for a concrete to soil contact when multiplied by the dead load. When combining passive pressure and frictional resistance, the passive pressure component should be reduced by one-third. All footing setbacks from slopes should comply with Figure 1808.7.1 of the 2013 CBC. GSI recommends a minimum horizontal setback distance of 7 feet as measured from the bottom, outboard edge of the footing to the slope face. Footings for structures adjacent to retaining walls should be deepened so as to extend below a 1:1 projection from the heel of the wall. Alternatively, walls may be designed to accommodate structural loads from buildings or appurtenances as described in the "Retaining Wall" section of this report. PRELIMINARY FOUNDATION CONSTRUCTION RECOMMENDATIONS The following foundation construction recommendations are presented as a minimum criteria from a soils engineering viewpoint. The following foundation construction recommendations are intended to support planned improvements underlain by at least Ron Ozaki 1645 Chestnut Avenue, Carlsbad FUe:e:\wpl2\7000\7014a.pge GeOSolls, Inc. W.O. 7014-A-SC February 22, 2016 Page 16 7 feet of non-detrimentally expansive soils (i.e., E.l.<21 and P1 <15). Although not anticipated based on the available data, should foundations be underlain by expansive soils they will require specific design to mitigate expansive soil effects as required in Sections 1808.6.1 or 1808.6.2 of the 2013 CBC. Exterior and interior footings should be founded into engineered fill at a minimum depth of 18 inches below the lowest adjacent grade, and a minimum width of 18 inches, for the planned, two story structure. Isolated, exterior column and panel pads, or wall footings, should be at least 24 inches, square, and founded at a minimum depth of 24 inches into properly engineered fill. All footings should be minimally reinforced with two No. 4 reinforcing bars, one placed near the top and one placed near the bottom of the footing. All interior and exterior column footings, and perimeter wall footings, should be tied together via grade beams in at least one direction. The grade beam should be at least 12 inches square in cross section, and should be provided with a minimum of one No.4 reinforcing bar at the top, and one No.4 reinforcing bar at the bottom of the grade beam. The base of the reinforced grade beam should be at the same elevation as the adjoining footings. A grade beam, reinforced as previously recommended and at least 12 inches square, should be provided across large (garage) entrances. The base of the reinforced grade beam should be at the same elevation as the adjoining footings. A minimum concrete slab-on-grade thickness of 5 inches is recommended. Recommendations for floor slab underlayment are presented in a later section of this report. Concrete slabs should be reinforced with a minimum of No. 3 reinforcement bars placed at 18-inch on centers, in two horizontally perpendicular directions (i.e., long axis and short axis). All slab reinforcement should be supported to ensure proper mid-slab height positioning during placement of the concrete. "Hooking" of reinforcement is not an acceptable method of positioning. Specific slab subgrade pre-soaking is recommended for these soil conditions. Prior to the placement of underlayment sand and vapor retarder, GSI recommends that the slab subgrade materials be moisture conditioned to at least optimum moisture content to a minimum depth of 12 inches. Slab subgrade pre-soaking should be evaluated by the geotechnical consultant within 72 hours of the placement of the underlayment sand and vapor retarder. Soils generated from footing excavations to be used onsite should be compacted to a minimum relative compaction of 90 percent of the laboratory standard Ron Ozaki W.O. 7014-A-SC 1645 Chestnut Avenue, Carlsbad February 22, 2016 FIle:e:\wp12\7000\7014a.pge GeOSoils, Inc. Page 17 (ASTM D 1557), whether the soils are to be placed inside the foundation perimeter or in the yard/right-of-way areas. This material must not alter positive drainage patterns that direct drainage away from the structural areas and toward the street. 9. Reinforced concrete mix design should conform to "Exposure Class Cl" in Table 4.2.1 of ACI-31 8-11 since concrete would likely be exposed to moisture. Foundation Settlement Provided that the earthwork and foundation recommendations in this reported are adhered foundations bearing on engineered fill should be minimally designed to accommodate a differential settlement of 3/4-iflCh over a 40-foot horizontal span (angular distortion = 1/640). SOIL MOISTURE TRANSMISSION CONSIDERATIONS GSI has evaluated the potential for vapor or water transmission through the concrete floor slab, in light of typical floor coverings and improvements. Please note that slab moisture emission rates range from about 2 to 27 lbs/ 24 hours/1,000 square feet from a typical slab (Kanare, 2005), while floor covering manufacturers generally recommend about 3 lbs/24 hours as an upper limit. The recommendations in this section are not intended to preclude the transmission of water or vapor through the foundation or slabs. Foundation systems and slabs shall not allow water or water vapor to enter into the structure so as to cause damage to another building component or to limit the installation of the type of flooring materials typically used for the particular application (State of California, 2016). These recommendations may be exceeded or supplemented by a water "proofing" specialist, project architect, or structural consultant. Thus, the client will need to evaluate the following in light of a cost vs. benefit analysis (owner expectations and repairs/replacement), along with disclosure to all interested/affected parties. It should also be noted that vapor transmission will occur in new slab-on-grade floors as a result of chemical reactions taking place within the curing concrete. Vapor transmission through concrete floor slabs as a result of concrete curing has the potential to adversely affect sensitive floor coverings depending on the thickness of the concrete floor slab and the duration of time between the placement of concrete, and the floor covering. It is possible that a slab moisture sealant may be needed prior to the placement of sensitive floor coverings if a thick slab-on-grade floor is used and the time frame between concrete and floor covering placement is relatively short. Considering the E.I. test results presented herein, and known soil conditions in the region, the anticipated typical water vapor transmission rates, floor coverings, and improvements (to be chosen by the Client and/or project architect) that can tolerate vapor transmission rates without significant distress, the following alternatives are provided: Concrete slabs should be thicker. Ron Ozaki W.O. 7014-A-SC 1645 Chestnut Avenue Carlsbad February 22, 2016 File:e:\wpl2\7000\7014a.pge GeoSoiI$ Inc. Page 18 Concrete slab underlayment should consist of a 15-mil vapor retarder, or equivalent, with all laps sealed per the 2013 CBC and the manufacturer's recommendation. The vapor retarder should comply with the ASTM E 1745 - Class A criteria, and be installed in accordance with ACI 302.1 R-04 and ASTM E 1643. The 10- to 15-mil vapor retarder (ASTM E 1745 - Class A) shall be installed per the recommendations of the manufacturer, including all penetrations (i.e., pipe, ducting, rebar, etc.). Concrete slabs, including the garage areas, shall be underlain by 2 inches of clean, washed sand (SE > 30) above a 15-mil vapor retarder (ASTM E-1 745 - Class A, per Engineering Bulletin 119 [Kanare, 2005]) installed per the recommendations of the manufacturer, including all penetrations (i.e., pipe, ducting, rebar, etc.). The manufacturer shall provide instructions for lap sealing, including minimum width of lap, method of sealing, and either supply or specify suitable products for lap sealing (ASTM E 1745), and per code. ACI 302.113-04 (2004) states "If a cushion or sand layer is desired between the vapor retarder and the slab, care must be taken to protect the sand layer from taking on additional water from a source such as rain, curing, cutting, or cleaning. Wet cushion or sand layer has been directly linked in the past to significant lengthening of time required for a slab to reach an acceptable level of dryness for floor covering applications." Therefore, additional observation and/or testing will be necessary for the cushion or sand layer for moisture content, and relatively uniform thicknesses, prior to the placement of concrete. The vapor retarder shall be underlain by 2 inches of sand (SE > 30) placed directly on the prepared, moisture conditioned, subgrade and should be sealed to provide a continuous retarder under the entire slab, as discussed above. As discussed previously, GSI indicated this layer of import sand may be eliminated below the vapor retarder, if laboratory testing indicates that the slab subgrade soil have a sand equivalent (SE) of 30 or greater, during site grading. Concrete should have a maximum water/cement ratio of 0.50. This does not supercede Table 4.2.1 of Chapter 4 of the ACI (2011) for corrosion or other corrosive requirements. Additional concrete mix design recommendations should be provided by the structural consultant and/or waterproofing specialist. Concrete finishing and workablity should be addressed by the structural consultant and a waterproofing specialist. Where slab water/cement ratios are as indicated herein, and/or admixtures used, the structural consultant should also make changes to the concrete in the grade beams and footings in kind, so that the concrete used in the foundation and slabs are designed and/or treated for more uniform moisture protection. Ron Ozaki W.O. 7014-A-SC 1645 Chestnut Avenue, Carlsbad February 22, 2016 F1e:e:\wp12\7000\7014a.pge GeoSods, Inc. Page 19 The owner(s) should be specifically advised which areas are suitable for tile flooring, vinyl flooring, or other types of water/vapor-sensitive flooring and which are not suitable. In all planned floor areas, flooring shall be installed per the manufactures recommendations. Additional recommendations regarding water or vapor transmission should be provided by the architect/structural engineer/slab or foundation designer and should be consistent with the specified floor coverings indicated by the architect. Regardless of the mitigation, some limited moisture/moisture vapor transmission through the slab should be anticipated. Construction crews may require special training for installation of certain product(s), as well as concrete finishing techniques. The use of specialized product(s) should be approved by the slab designer and water-proofing consultant. A technical representative of the flooring contractor should review the slab and moisture retarder plans and provide comment prior to the construction of the foundations or improvements. The vapor retarder contractor should have representatives onsite during the initial installation. WALL DESIGN PARAMETERS General Recommendations for the design and construction of conventional masonry retaining walls are provided herein. Recommendations for specialty walls (i.e., crib, earthstone, geogrid, etc.) can be provided upon request, and would be based on site specific conditions. Conventional Retaining Walls The design parameters provided below assume that either very low expansive soils (typically Class 2 permeable filter material or Class 3 aggregate base) 2r native onsite materials with an expansion index up to 20 are used to backfill any retaining wall. Please note that the onsite likely do not meet this criteria. The type of backfill (i.e., select or native), should be specified by the wall designer, and clearly shown on the plans. Building walls, below grade, should be water-proofed. Waterproofing should also be provided for site retaining walls in order to reduce the potential for efflorescence staining. Preliminary Retaining Wall Foundation Design Preliminary foundation design for retaining walls should incorporate the following recommendations: Minimum Footing Embedment - 18 inches below the lowest adjacent grade (excluding landscape layer [upper 6 inches]). Ron Ozaki W.O. 7014-A-SC 1645 Chestnut Avenue, Carlsbad February 22, 2016 File:e:\wp12\7000\7014a.pge GeoSoUs,Inc. Page 20 Minimum Footing Width - 24 inches Allowable Bearing Pressure - An allowable bearing pressure of 2,500 pcf may be used in the preliminary design of retaining wall foundations provided that the footing maintains a minimum width of 24 inches and extends at least 18 inches into approved engineered fill overlying dense formational materials. This pressure may be increased by one-third for short-term wind and/or seismic loads. Passive Earth Pressure - A passive earth pressure of 250 pcf with a maximum earth pressure of 2,500 psf may be used in the preliminary design of retaining wall foundations provided the foundation is embedded into properly compacted silty to clayey sand fill. Lateral Sliding Resistance - A 0.35 coefficient of friction may be utilized for a concrete to soil contact when multiplied by the dead load. When combining passive pressure and frictional resistance, the passive pressure component should be reduced by one-third. Backfill Soil Density - Soil densities ranging between 110 pcf and 115 pcf may be used in the design of retaining wall foundations. This assumes an average engineered fill compaction of at least 90 percent of the laboratory standard (ASTM D 1557). Any retaining wall footings near the perimeter of the site will likely need to be deepened into unweathered very old paralic deposits or unweathered Santiago Formation for adequate vertical and lateral bearing support. All retaining wall footing setbacks from slopes should comply with Figure 1808.7.1 of the 2013 CBC. GSl recommends a minimum horizontal setback distance of 7 feet as measured from the bottom, outboard edge of the footing to the slope face. Restrained Walls Any retaining walls that will be restrained prior to placing and compacting backfill material or that have re-entrant or male corners, should be designed for an at-rest equivalent fluid pressure (EFP) of 55 pcf and 65 pcf for select and very low expansive native backfill, respectively. The design should include any applicable surcharge loading. For areas of male or re-entrant corners, the restrained wall design should extend a minimum distance of twice the height of the wall (2H) laterally from the corner. Cantilevered Walls The recommendations presented below are for cantilevered retaining walls up to 10 feet high. Design parameters for walls less than 3 feet in height may be superceded by County of San Diego regional standard design. Active earth pressure may be used for retaining wall design, provided the top of the wall is not restrained from minor deflections. An Ron Ozaki W.O. 7014-A-SC 1645 Chestnut Avenue, Carlsbad February 22, 2016 File:e:\wp12\7000\7014a.pge GeOSOlIS, Inc. Page 21 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 due to traffic, structures, seismic events or adverse geologic conditions. When wall configurations are finalized, the appropriate loading conditions for superimposed loads can be provided upon request. For preliminary planning purposes, the structural consultant/wall designer should incorporate the surcharge of traffic on the back of retaining walls where vehicular traffic could occur within horizontal distance "H" from the back of the retaining wall (where "H" equals the wall height). The traffic surcharge may be taken as 100 psf/ft in the upper 5 feet of backfill for light truck and cars traffic. This does not include the surcharge of parked vehicles which should be evaluated at a higher surcharge to account for the effects of seismic loading. Equivalent fluid pressures for the design of cantilevered retaining walls are provided in the following table: SURFACE SLOPE OF RETAINED MATERIAL (HORIZONTAL:VERTICAL) EQUIVALENT FLUID WEIGHT P.C.F. (SELECT BACKFILL) EQUIVALENT FLUID WEIGHT P.C.F. (NATIVE BACKFILL) Level(') 38 1 50 1 2tol 55 60 (')Level backfill behind a retaining wall is defined as compacted earth materials, properly drained, without a slope for a distance of 2H behind the wall, where H is the height of the wall. SE > 30, P.1. < 15, E.I. < 21, and < 10% passing No. 200 sieve. E.I. = 0 to 50, SE > 30, P.1. < 15, E.I. < 21, and _<, 15% passing No. 200 sieve. Seismic Surcharge For engineered retaining walls with more than 6 feet of retained materials, as measured vertically from the bottom of the wall footing at the heel to daylight, GSI recommends that the walls be evaluated for a seismic surcharge (in general accordance with 2013 CBC requirements). The site walls in this category should maintain an overturning Factor-of-Safety (FOS) of approximately 1.25 when the seismic surcharge (increment), is applied. For restrained walls, the seismic surcharge should be applied as a uniform surcharge load from the bottom of the footing (excluding shear keys) to the top of the backfill at the heel of the wall footing. This seismic surcharge pressure (seismic increment) may be taken as 15H where "H" for retained walls is the dimension previously noted as the height of the backfill to the bottom of the footing. The resultant force should be applied at a distance 0.6 H up from the bottom of the footing. For the evaluation of the seismic surcharge, the bearing pressure may exceed the static value by one-third, considering the transient nature of this surcharge. For cantilevered walls, the pressure should be applied as an inverted triangular distribution using 15H. For restrained walls, the pressure should be applied as a rectangular distribution. Please note this is for local wall stability only. Ron Ozaki W.O. 7014-A-SC 1645 Chestnut Avenue, Carlsbad February 22, 2016 File:e:\wp12\7000\7014a.pge GOSOdS, Inc. Page 22 The 15H is derived from a Mononobe-Okabe solution for both restrained cantilever walls. This accounts for the increased lateral pressure due to shakedown or movement of the sand fill soil in the zone of influence from the wall or roughly a 45 - 4)12 plane away from the back of the wall. The 15H seismic surcharge is derived from the formula: P=%';' yH Where: Pb = Seismic increment a, = Probabilistic horizontal site acceleration with a percentage of = total unit weight (115 to 125 pcf for site soils @ 90% relative compaction). H = Height of the wall from the bottom of the footing or point of pile fixity. Retaining Wall Backfill and Drainage Positive drainage must be provided behind all retaining walls in the form of gravel wrapped in geofabric and outlets. A backdrain system is considered necessary for retaining walls that are 2 feet or greater in height. Details 1, 2, and 3, present the back drainage options discussed below. Backdrains should consist of a 4-inch diameter perforated PVC or ABS pipe encased in either Class 2 permeable filter material or 3/4-IflCh to 1 1/2-iflCh gravel wrapped in approved filter fabric (Mirafi 140 or equivalent). For low expansive backfill, the filter material should extend a minimum of 1 horizontal foot behind the base of the walls and upward at least 1 foot. For native backfill that has up to medium expansion potential, continuous Class 2 permeable drain materials should be used behind the wall. This material should be continuous (i.e., full height) behind the wall, and it should be constructed in accordance with the enclosed Detail 1 (Typical Retaining Wall Backfill and Drainage Detail). For limited access and confined areas, (panel) drainage behind the wall may be constructed in accordance with Detail 2 (Retaining Wall Backfill and Subdrain Detail Geotextile Drain). Materials with an E.I. potential of greater than 50 should not be used as backfill for retaining walls. For more onerous expansive situations, backfill and drainage behind the retaining wall should conform with Detail 3 (Retaining Wall And Subdrain Detail Clean Sand Backfill). Drain outlets should consist of a 4-inch diameter solid PVC or ABS pipe spaced no greater than ± 100 feet apart, with a minimum of two outlets, one on each end. The use of weep holes, only, in walls higher than 2 feet, is not recommended. The surface of the backfill should be sealed by pavement or the top 18 inches compacted with native soil (E.l. <50). Proper surface drainage should also be provided. For additional mitigation, consideration should be given to applying a water- proof membrane to the back of all retaining structures. The use of a waterstop should be considered for all concrete and masonry joints. Ron Ozaki W.O. 7014-A-SC 1 645 Chestnut Avenue, Carlsbad February 22, 2016 R1e:e:\wp12\7000\7014a.pge GeoSoils, Inc. Page 23 (1) Waterproofing membrane CMU or reinforced-concrete wall Structural footing or settlement-sensitive improvement j— Provide surface drainage via an / engineered V-ditch (see civil plans for details) 21 NO slope 12:hed L.;.: •........•....-1..• (2) Gravel Native backfill 1:1 (h:v) or flatter backcut to be properly benched Proposed grade I sloped to drain per precise civil drawings (5) Weep hole Footing and wall design by others (6) Footing Waterproofing membrane. Grave Clean, crushed, 34 to 1Y2 inch. Fitter fabric: Mirafi 140N or approved equivalent. Pipe 4-inch-diameter perforated PVC, Schedule 40, or approved alternative with minimum of 1 percent gradient sloped to suitable, approved outlet point (perforations down). Weep hole: Minimum 2-inch diameter placed at 20-foot centers along the wall and placed 3 inches above finished surface. Design civil engineer to provide drainage at toe of wall. No weep holes for below-grade walls. Footing: If bench is created behind the footing greater than the footing width, use level fill or cut natural earth materials. An additional "heel" drain will likely be required by geotechnical consultant. G ~ VS i a ~j 1, 5i lin C. RETAINING WALL DETAIL - ALTERNATIVE A Detail 1 C Structural footing or (1) Waterproofing settlement-sensitive improvement membrane (optional) Provide surface drainage via engineered V-ditch (see civil plan details) CMU or 2.1 NO slope reinforced-concrete wall 6chea . •. ..•. . : - (2) Composite :.*7." • drairt. •. .-...... (5) Weep hole— \\ j— Proposed grade Native backfill / sloped to drain I per precise civil . drawings . •.... (4) I _____ ____ ____ •.:: .7 . .. T: :. 1:1 NO or flatter .. backcut to be Footing and wall properly benched design by others — (6) 1 cubic foot of 3%-inch crushed rock S (7) Footing (1) Waterproofing membrane (optional): Liquid boot or approved mastic equivalent. Drain: Miradrain 6000 or J-drain 200 or equivalent f or non-waterproofed walls; Miradrain 6200 or J-drain 200 or equivalent for waterproofed walls (all perforations down). Filter fabric: Mirafi 140N or approved equivalent; place fabric flap behind core. Pipe: 4-inch-diameter perforated PVC, Schedule 40, or approved alternative with minimum of 1 percent gradient to proper outlet point (perforations down). Weep hole: Minimum 2-inch diameter placed at 20-foot centers along the wall and placed 3 inches above finished surface. Design civil engineer to provide drainage at toe of wall. No weep holes for below-grade walls. Gravel: Clean, crushed, % to IY2 inch. Footing: If bench is created behind the footing greater than the footing width, use level fill or cut natural earth materials. An additional "heel" drain will likely be required by geotechnical consultant Ge4 —1oih hjc. RETAINING WALL DETAIL - ALTERNATIVE B Detail 2 . Structural footing or settlement-sensitive improvement Provide surface drainage 21 NO slope (1) Waterproofing membrane CMUor reinforced-concrete wall 4 ±12 ö,ches 1 (5) Weep hole H -- Proposed grade / sloped to drain J per precise civil T drawings Footing and wall design by others Heel jdthi .bric (2) Gravel - (4) Pipe '•- (7) Footing - (8) Native backfill (6) Clean sand backfill - 1:1 (hv) or flatter backcut to be properly benched Waterproofing membrane Liquid boot or approved masticequivalent Gravel: Clean, crushed, 3/4 to JY2 inch. Alter fabric: Mirafi 1.40N or approved equivalent. Pipe: 4-inch-diameter perforated PVC, Schedule 40, or approved alternative with minimum of 1 percent gradient to proper outlet point (perforations down). Weep hole: Minimum 2-inch diameter placed at 20-foot centers along the wall and placed 3 inches above finished surface. Design civil engineer to provide drainage at toe of wall. No weep holes for below-grade walls. Clean sand backfill: Must have sand equivalent value (S.E.) of 35 or greater; can be densified by water jetting upon approval by geotechnical engineer. Footing If bench is created behind the footing greater than the footing width, use level fill or cut natural earth materials. An additional "heel" drain will likely be required by geotechnical consultant Native backfill: If E.I. (21 and S.E. )35 then all sand requirements also may not be required and will be reviewed by the geotechnical consultant. RETAINING WALL DETAIL - ALTERNATIVE C J Detail 3 Wall/Retaining Wall Footing Transitions Site walls are anticipated to be founded on footings designed in accordance with the recommendations in this report. Although not anticipated, should wall footings transition from cut to fill, the civil designer may specify either: A minimum of a 2-foot overexcavation and recompaction of cut materials for a distance of 2H,.from the point of transition. Increase of the amount of reinforcing steel and wall detailing (i.e., expansion joints or crack control joints) such that a angular distortion of 1/360 for a distance of 2H on either side of the transition may be accommodated. Expansion joints should be placed no greater than 20 feet on-center, in accordance with the structural engineer's/wall designer's recommendations, regardless of whether or not transition conditions exist. Expansion joints should be sealed with a flexible, non-shrink grout. Embed the footings entirely into native formational material (i.e., deepened footings). If transitions from cut to fill transect the wall footing alignment at an angle of less than 45 degrees (plan view), then the designer should follow recommendation "a" (above) and until such transition is between 45 and 90 degrees to the wall alignment. DRIVEWAY/PARKING, FLATWORK,, AND OTHER IMPROVEMENTS The effects of expansive soils are cumulative, and typically occur over the lifetime of any improvements. On relatively level areas, when the soils are allowed to dry, the dessication and swelling process tends to cause heaving and distress to flatwork and other improvements. The resulting potential for distress to improvements may be reduced, but not totally eliminated. To that end, it is important that the homeowner be aware of this long-term potential for distress. To reduce the likelihood of distress, the following recommendations are presented for all exterior flatwork: The subgrade area for concrete slabs should be compacted to achieve a minimum 90 percent relative compaction (sidewalks, patios), and 95 percent relative compaction (traffic pavements), and then be presoaked to 2 to 3 percentage points above (or 125 percent of) the soils' optimum moisture content, to a depth of 18 inches below subgrade elevation. If very low expansive soils are present, only optimum moisture content, or greater, is required and specific presoaking is not warranted. The moisture content of the subgrade should be proof tested within 72 hours prior to pouring concrete. 2. Concrete slabs should be cast over a non-yielding surface, consisting of a 4-inch layer of crushed rock, gravel, or clean sand, that should be compacted and level Ron Ozaki W.O. 7014-A-SC 1645 Chestnut Avenue, Carlsbad February 22, 2016 File:e:\wp12\7000\7014a.pge GeoSoils, Inc. Page 27 prior to pouring concrete. If very low expansive soils are present, the rock or gravel or sand may be deleted. The layer or subgrade should be wet-down completely prior to pouring concrete, to minimize loss of concrete moisture to the surrounding earth materials. Exterior, non-vehicle slabs (sidewalks, patios, etc.) should be a minimum of 4 inches thick. Driveway and parking area concrete slabs and approaches should be at least 6 inches thick. A thickened edge (12 inches) should also be considered adjacent to all landscape areas, to help impede infiltration of landscape water under the slab(s). All pavement construction should minimally be performed in general accordance with industry standards and properly transitioned. Asphaltic parameters should minimally consist of 4 inches asphalt over 4 inches of compacted aggregate base per the City. Trash truck loading areas should be designed per Carlsbad City standard drawings (City of Carlsbad, 1993). The use of transverse and longitudinal control joints are recommended to help control slab cracking due to concrete shrinkage or expansion. Two ways to mitigate such cracking are: a) add a sufficient amount of reinforcing steel, increasing tensile strength of the slab; and, b) provide an adequate amount of control and/or expansion joints to accommodate anticipated concrete shrinkage and expansion. In order to reduce the potential for unsightly cracks, slabs should be reinforced at mid-height with a minimum of No. 3 bars placed at 18 inches on center, in each direction. If subgrade soils within the top 7 feet from finish grade are very low expansive soils (i.e., E.I. :520), then 6x6-W1.4xW1.4 welded-wire mesh may be substituted for the rebar, provided the reinforcement is placed on chairs, at slab mid-height. The exterior slabs should be scored or saw cut, ½ to 3/8 inches deep, often enough so that no section is greater than 10 feet by 10 feet. For sidewalks or narrow slabs, control joints should be provided at intervals of every 6 feet. The slabs should be separated from the foundations and sidewalks with expansion joint filler material. No traffic should be allowed upon the newly poured concrete slabs until they have been properly cured to within 75 percent of design strength. Concrete compression strength should be a minimum of 2,500 psi for sidewalks and patios, and a minimum 3,250 psi for traffic pavements. Driveways, sidewalks, and patio slabs adjacent to the structure should be separated from the structure with thick expansion joint filler material. In areas directly adjacent Ron Ozakl W.O. 7014-A-SC 1645 Chestnut Avenue, Carlsbad February 22, 2016 File:e:\wp12\7000\7014a.pge GeoSoils, Inc. Page 28 to a continuous source of moisture (i.e., irrigation, planters, etc.), all joints should be additionally sealed with flexible mastic. Planters and walls should not be tied to the structure. Overhang structures should be supported on the slabs, or structurally designed with continuous footings tied in at least two directions. If very low expansion soils are present, footings need only be tied in one direction. Any masonry landscape walls that are to be constructed throughout the property should be grouted and articulated in segments no more than 20 feet long. These segments should be keyed or doweled together. Utilities should be enclosed within a closed utilidor (vault) or designed with flexible cqnnections to accommodate differential settlement and expansive soil conditions. Positive site drainage should be maintained at all times. Finish grade on the lot should provide a minimum of 1 to 2 percent fall to the street, as indicated herein. It should be kept in mind that drainage reversals could occur, including post-construction settlement, if relatively flat yard drainage gradients are not periodically maintained by the homeowner. Air conditioning (A/C) units should be supported by slabs that are incorporated into the building foundation or constructed on a rigid slab with flexible couplings for plumbing and electrical lines. A/C waste water lines should be drained to a suitable non-erosive outlet. Shrinkage cracks could become excessive if proper finishing and curing practices are not followed. Finishing and curing practices should be performed per the Portland Cement Association Guidelines. Mix design should incorporate rate of curing for climate and time of year, sulfate content of soils, corrosion potential of soils, and fertilizers used on site. DEVELOPMENT CRITERIA Onsite Storm Water Treatment Based on our evaluation, onsite storm water treatment systems should consider the following: Site soils (i.e., proposed compacted fill) are considered to belong to hydrologic subgroup "D." Ron Ozaki W.O. 7014-A-SC 1645 Chestnut Avenue, Carlsbad February 22, 2016 FiIe:e:\wp12\7000\7014a.pge GeoSoils, Inc. Page 29 The presence of the thin surficial fill layer overlying dense formational soil will increase the potential for the development of a perched water table along the fill/formation contact. The will be an increased potential for the adverse performance of structures, should the engineered fills supporting the proposed structures become saturated, due to settlement, or water vapor transmission. Impermeable liners and subdrains should be used along the bottom of bioretention swales/basins located within the influence of improvements on slopes. Impermeable liners used in conjunction with bioretention basins should consist of a 30-mil polyvinyl chloride (PVC) membrane that is covered by a minimum of 12 inches of clean soil, free from rocks and debris, with a maximum 4:1 (h:v) slope inclination, or flatter, and meets the following minimum specifications: Specific Gravity (ASTM D792): 1.2 (g/cc, mm.); Tensile (ASTM D882): 73 (lb/in-width, mm); Elongation at Break (ASTM D882): 380 (%, mm); Modulus (ASTM D882): 30 (lb/in-width, mm.); and Tear Strength (ASTM D1004):8 (lb/in, mm); Seam Shear Strength (ASTM D882) 58.4 (lb/in, mm); Seam Peel Strength (ASTM D882) 15 (lb/in, mm). Subdrains should consist of at least 4-inch diameter Schedule 40 or SDR 35 drain pipe with perforations oriented down. The drain pipe should be sleeved with a filter sock, then tight-lines, and directed to a suitable outlet. In practice, storm water BMP's are usually initially designed by the project design civil engineer. Selection of methods should include (but should not be limited to) review by licensed professionals including the geotechnical engineer, hydrogeologist, engineering geologist, project civil engineer, landscape architect, environmental professional, and industrial hygienist. Applicable governing agency requirements should be reviewed and included in design considerations. Slope Maintenance and Planting Water has been shown to weaken the inherent strength of all earth materials. Slope stability is significantly reduced by overly wet conditions. Positive surface drainage away from slopes should be maintained and only the amount of irrigation necessary to sustain plant life should be provided for planted slopes. Over-watering should be avoided as it adversely affects site improvements, and causes perched groundwater conditions. Graded slopes constructed utilizing onsite materials would be erosive. Eroded debris may be minimized and surficial slope stability enhanced by establishing and maintaining a suitable vegetation cover soon after construction. Compaction to the face of fill slopes would tend to minimize short-term erosion until vegetation is established. Plants selected for landscaping should be light weight, deep rooted types that require little water and are Capable of surviving the prevailing climate. Jute-type matting or other fibrous covers may Ron Ozaki W.O. 7014-A-SC 1645 Chestnut Avenue, Carlsbad February 22, 2016 FIIe:e:\wp12\7000\7014a.pge G°Soi1s Inc. Page 30 aid in allowing the establishment of a sparse plant cover. Utilizing plants other than those recommended above will increase the potential for perched water, staining, mold, etc., to develop. A rodent control program to prevent burrowing should be implemented. Irrigation of natural (ungraded) slope areas is generally not recommended. These recommendations regarding plant type, irrigation practices, and rodent control should be provided to all interested/affected parties. Over-steepening of slopes should be avoided during building construction activities and landscaping. Drainage Adequate surface, drainage is a very important factor in reducing the likelihood of adverse performance of foundations, hardscape, and slopes. Surface drainage should be sufficient to mitigate ponding of water anywhere on the property, and especially near structures and tops of slopes. Surface drainage should be carefully taken into consideration during fine grading, landscaping, and building construction. Therefore, care should be taken that future landscaping or construction activities do not create adverse drainage conditions. Positive site drainage within the property should be provided and maintained at all times. Drainage should not flow uncontrolled down any descending slope. Water should be directed away from foundations and tops of slopes, and not allowed to pond and/or seep into the ground. In general, site drainage should conform to Section 1804.3 of the 2013 CBC. Consideration should be given to avoiding construction of planters adjacent to structures (buildings, pools, spas, etc.). Building pad drainage should be directed toward the street or other approved area(s). Although not a geotechnical requirement, roof gutters, down spouts, or other appropriate means may be utilized to control roof drainage. Down spouts, or drainage devices should outlet a minimum of 5 feet from structures or into a subsurface drainage system. Areas of seepage may develop due to irrigation or heavy rainfall, and should be anticipated. Minimizing irrigation will lessen this potential. If areas of seepage develop, recommendations for minimizing this effect could be provided upon request. Erosion Control Cut and fill slopes will be subject to surficial erosion during and after grading. Onsite earth materials have a moderate to high erosion potential. Consideration should be given to providing hay bales and silt fences for the temporary control of surface water, from a geotechnical viewpoint. Landscape Maintenance Only the amount of irrigation necessary to sustain plant life should be' provided. Over-watering the landscape areas will adversely affect proposed site improvements. We would recommend that any proposed open-bottom planters adjacent to proposed structures be eliminated for a minimum distance of 10 feet. As an alternative, closed-bottom type planters could be utilized. An outlet placed in the bottom of the planter, could be installed to direct drainage away from structures or any exterior concrete Ron Ozaki W.O. 7014ASC 1645 Chestnut Avenue, Carlsbad February 22, 2016 FIIe:e:\wp12\7000\7014a.pge GeoSoils, Inc. Page 31 flatwork. If planters are constructed adjacent to structures, the sides and bottom of the planter should be provided with a moisture retarder to prevent penetration of irrigation water into the subgrade. Provisions should be made to drain the excess irrigation water from the planters without saturating the subgrade below or adjacent to the planters. Graded slope areas should be planted with drought resistant vegetation. Consideration should be given to the type of vegetation chosen and their potential effect upon surface improvements (i.e., some trees will have an effect on concrete flatwork with their extensive root systems). From a geotechnical standpoint leaching is not recommended for establishing landscaping. If the surface soils are processed for the purpose of adding amendments, they should be recompacted to 90 percent minimum relative compaction. Gutters and Downspouts As previously discussed in the drainage section, the installation of gutters and downspouts should be considered to collect roof water that may otherwise infiltrate the soils adjacent to the structures. If utilized, the downspouts should be drained into PVC collector pipes or other non-erosive devices (e.g., paved swales or ditches; below grade, solid tight-lined PVC pipes; etc.), that will carry the .water away from the structure, to an appropriate outlet, in accordance with the recommendations of the design civil engineer. Downspouts and gutters are not a requirement; however, from a geotechnical viewpoint, provided that positive drainage is incorporated into project design (as discussed previously). Subsurface and Surface Water Subsurface and surface water are not anticipated to affect site development, provided that the recommendations contained in this report are incorporated into final design and construction and that prudent surface and subsurface drainage practices are incorporated into the construction plans. Perched groundwater conditions along zones of contrasting permeabilities may not be precluded from occurring in the future due to site irrigation, poor drainage conditions, or damaged utilities, and should be anticipated. Should perched groundwater conditions develop, this office could assess the affected area(s) and provide the appropriate recommendations to mitigate the observed groundwater conditions. Groundwater conditions may change with the introduction of irrigation, rainfall, or other factors. Site Improvements If in the future, any additional improvements (e.g., pools, spas, etc.) are planned for the site, recommendations concerning the geological or geotechnical aspects of design and construction of said improvements could be provided upon request. Pools and/or spas should not be constructed without specific design and construction recommendations from GSI, and this construction recommendation should be provided to all interested/affected parties. This office should be notified in advance of any fill placement, grading of the site, or trench backfllling after rough grading has been completed. This includes any grading, utility trench and retaining wall backfills, flatwork, etc. Ron Ozaki W.O. 7014-A-SC 1645 Chestnut Avenue, Carlsbad February 22, 2016 File:e:\wp12\7000\7014a.pge GeOSO1IS, Inc. Page 32 Tile Flooring Tile flooring can crack, reflecting cracks in the concrete slab below the tile, although small cracks in a conventional slab may not be significant. Therefore, the designer should consider additional steel reinforcement for concrete slabs-on-grade where tile will be placed. The tile installer should consider installation methods that reduce possible cracking of the tile such as slipsheets. Slipsheets or a vinyl crack isolation membrane (approved by the Tile Council of America/Ceramic Tile Institute) are recommended between tile and concrete slabs on grade. Additional Grading This office should be notified in advance of any fill placement, supplemental regrading of the site, or trench backfihling after rough grading has been completed. 'This includes completion of grading in the street, driveway approaches, driveways, parking areas, and utility trench and retaining wall backfihls. Footing Trench Excavation All footing excavations should be observed by a representative of this firm subsequent to trenching and prior to concrete form and reinforcement placement. The purpose of the observations is to evaluate that the excavations have been made into the recommended bearing material and to the minimum widths and depths recommended for construction. If loose or compressible materials are exposed within the footing excavation, a deeper footing or removal and recompaction of the subgrade materials would be recommended at that time. Footing trench spoil and any excess soils generated from utility trench excavations should be compacted to a minimum relative compaction of 90 percent, if not removed from the site. Trench ing/Temporary Construction Backcuts Considering the nature of the onsite earth materials, it should be anticipated that caving or sloughing could be a factor in subsurface excavations and trenching. Shoring or excavating the trench walls/backcuts at the angle of repose (typically 25 to 45 degrees [except as specifically superceded within the text of this report]), should be anticipated. All excavations should be observed by an engineering geologist or soil engineer from GSI, prior to workers entering the excavation or trench, and minimally conform to CAL-OSHA, state, and local safety codes. Should adverse conditions exist, appropriate recommendations would be offered at that time. The above recommendations should be provided to any contractors and/or subcontractors, or homeowners, etc., that may perform such work. Ron Ozaki W.O. 7014-A-SC 1645 Chestnut Avenue, Carlsbad February 22, 2016 FiIe:e:\wpl2\7000\7014a.pge GeoSoils,Inc. Page 33 Utility Trench Backfill All interior utility trench backfill should be brought to at least 2 percent above optimum moisture content and then compacted to obtain a minimum relative compaction of 90 percent of the laboratory standard. As-an alternative for shallow (1 2-inch to 18-inch) under-slab trenches, sand having a sand equivalent value of 30 or greater maybe utilized and jetted or flooded into place. Observation, probing and, testing should be provided to evaluate the desired results. Exterior trenches adjacent to, and within areas extending below a 1:1 plane projected from the outside bottom edge of the footing, and all trenches beneath hardscape features and in slopes, should be compacted to at least 90 percent of the laboratory standard. Sand backfill, unless excavated from the trench, should not be used in these backfill areas. Compaction testing and observations, along with probing, should be accomplished to evaluate the desired results. All trench excavations should conform to CAL-OSHA, state, and local safety codes. Utilities crossing grade beams, perimeter beams, or footings should either pass below the footing or grade beam utilizing a hardened collar or foam spacer, or pass through the footing or grade beam in accordance with the recommendations of the structural engineer. SUMMARY OF RECOMMENDATIONS REGARDING GEOTECHNICAL OBSERVATION AND TESTING We recommend that observation and/or testing be performed by GSI at each of the following construction stages: During grading/recertification. During excavation. During placement of subdrains or other subdrainage devices, prior to placing fill and/or backfill. After excavation of building footings, retaining wall footings, and free standing walls footings, prior to the placement of reinforcing steel or concrete. Prior to pouring any slabs or flatwork, after presoaking/presaturation of building pads and other fiatwork subgrade, before the placement of concrete, reinforcing steel, capillary break (i.e., sand, pea-gravel, etc.), or vapor retarders (i.e., visqueen, etc.). Ron Ozaki W.O. 7014-A-SC 1645 Chestnut Avenue, Carlsbad February 22, 2016 F1le:e:\wp12\7000\7014a.pge GeOSolls, Inc. Page 34 During retaining wall subdrain installation, prior to backfill placement. During placement of backfill for area drain, interior plumbing, utility line trenches, and retaining wall backfill. During slope construction/repair. When any unusual soil conditions are encountered during any construction operations, subsequent to the issuance of this report. When any homeowner improvements, such asfiatwork, spas, pools, walls, etc., are constructed, prior to construction. A report of geotechnical observation and testing should be provided at the. conclusion of each of the above stages, in order to provide concise and clear documentation of site work, and/or to comply with code requirements. OTHER DESIGN PROFESSIONALS/CONSULTANTS The design civil engineer, structural engineer, post-tension designer, architect, landscape architect, wall designer, etc., should review the recommendations provided herein, incorporate those recommendations into all their respective plans, and by explicit reference, make this report part of their project plans. This report presents minimum design criteria forthe design of slabs, foundations and other elements possibly applicable to the project. These criteria should not be considered as substitutes for actual designs by the structural engineer/designer. Please note that the recommendations contained herein are not intended to preclude the transmission of water or vapor through the slab or foundation. The structural engineer/foundation and/or slab designer should provide recommendations to not allow water or vapor to enter into the structure so as to cause damage to another building component, or so as to limit the installation of the type of flooring materials typically used for the particular application. The structural engineer/designer should analyze actual soil-structure interaction and consider, as needed, bearing, expansive soil influence, and strength, stiffness and deflections in the various slab, foundation, and other elements in order to develop appropriate, design-specific details. As conditions dictate, it is possible that other influences will also have to be considered. The structural engineer/designer should consider all applicable codes and authoritative sources where needed. If analyses by the structural engineer/designer result in less critical details than are provided herein as minimums, the minimums presented herein should be adopted. It is considered likely that some, more restrictive details will be required. If the structural engineer/designer has any questions or requires further assistance, they should not hesitate to call or otherwise transmit their requests to GSI. In order to mitigate Ron Ozaki W.O. 7014-A..sc 1645 Chestnut Avenue, Carlsbad February 22, 2016 Rle:e:\wp12\7000\7014a.pge GeoSoils, Inc. Page 35. potential distress, the foundation and/or improvement's designer should confirm to GSI and the governing agency, in writing, that the proposed foundations and/or improvements can tolerate the amount of differential settlement and/or expansion characteristics and other design criteria specified herein. PLAN REVIEW Final project plans (grading, precise grading, foundation, retaining wall, Landscaping, etc.), should be reviewed by this office prior to construction, so that construction is in accordance with the conclusions and recommendations of this report. Based on our review, supplemental recommendations and/or further geotechnical studies may be warranted. LIMITATIONS The materials encountered on the project site and utilized for our analysis are believed representative of the area; however, soil and bedrock materials vary in character between excavations and natural outcrops or conditions exposed during mass grading. Site conditions may vary due to seasonal changes or other factors. Inasmuch as ourstudy is based upon our review and engineering analyses and laboratory data, the conclusions and recommendations are professional opinions. These opinions have been derived in accordance with current standards of practice, and no warranty, either express or implied, is given. Standards of practice are subject to change with time. GSI assumes no responsibility or liability for work or testing performed by others, or their inaction; or work performed when OSI is not requested to be onsite, to evaluate if our recommendations have been properly implemented. Use of this report constitutes an agreement and consent by the user to all the limitations outlined above, notwithstanding any other agreements that may be in place. In addition, this report may be subject to review by the controlling authorities. Thus, this report brings to completion our scope of services for this portion of the project. All samples will be disposed of after 30 days, unless specifically requested by the client, in writing. Ron Ozaki W.O. 7014-A-SC 1645 Chestnut Avenue, Carlsbad February 22, 2016 Rle:e:\wpl2\7000\7014a.pge GeoSofts, Inc. Page 36 APPENDIX A REFERENCES Geo$oils, Inc. APPENDIX A REFERENCES American Concrete Institute, 2011, Building code requirements for structural concrete (ACI 318-11), an ACI standard and commentary: reported by ACI Committee 318; dated May 24. ACI Committee 302, 2004, Guide for concrete floor and slab construction, ACI 302.1 R-04, dated June. American Society for Testing and Materials (ASTM), 1998, Standard practice for installation of water vapor retarder used in contact with earth or granular fill under concrete slabs, Designation: E 1643-98 (Reapproved 2005). 1997, Standard specification for plastic water vapor retarders used in contact with soil or granular fill under concrete slabs, Designation: E 1745-97 (Reapproved 2004). American Society of Civil Engineers, 2010, Minimum design loads for buildings and other structures, ASCE Standard ASCE/SEI 7-10. Blake, Thomas F., 2000a, EQFAULT, A computer program for the estimation of peak horizontal acceleration from 3-1) fault sources; Windows 95/98 version. 2000b, EQSEARCH, A computer program for the estimation of peak horizontal acceleration from California historical earthquake catalogs; Updated to December 2009, Windows 95/98 version. Bozorgnia, V., Campbell K.W., and Niazi, M., 1999, Vertical ground motion: Characteristics, relationship with horizontal component, and building-code implications; Proceedings of the 5M1P99 seminar on utilization of strong-motion data, September 15, Oakland, pp. 23-49. 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 GeologicalSurvey, Special Publication 42, interim revision. California Building Standards Commission, 2013, California Building Code, California Code of Regulations, Title 24, Part 2, Volume 2 of 2, Based on the 2012 International Building Code, 2013 California Historical Building Code, Title 24, Part 8; 2013 California Existing Building Code, Title 24, Part 10. Cao, T., Bryant, W.A., Rowshandel, B., Branum, 0., and Wills, C.J., 2003, The revised 2002 California probabilistic seismic hazard maps, dated June, http://www.conservation .ca.gov/cgs/rghm/psha/fault_parameters/pdf/Documents /2002_CA_Hazard_Maps. pdf GeoSoils, Inc. Carlsbad, City of, 1993, Standards for design and construction of public works improvements in the City of Carlsbad. Jennings, C.W., 1994, Fault activity map of California and adjacent areas: California Division of Mines and Geology, Map Sheet No. 6, scale 1:750,000. Kanare, H.M., 2005, Concrete floors and moisture, Engineering Bulletin 119, Portland Cement Association. Kennedy, M.P., and Tan, SS., 2007, Geologic map of the Oceanside 30' by 60' quadrangle, California, regional geologic map series, scale 1:100,000, California Geologic Survey Map No. 2. Romanoff, M., 1957, Underground corrosion, originally issued April 1. Seed, 2005, Evaluation and mitigation of soil liquefaction hazard "evaluation of field data and procedures for evaluating the risk of triggering (or inception) of liquefaction", in Geotechnical earthquake engineering; short course, San Diego, California, April 8-9. Sowers and Sowers, 1979, Unified soil classification system (After U. S. Waterways Experiment Station and ASTM 02487-667) in Introductory Soil Mechanics, New York. State of California, 2016, Civil Code, Sections 895 et seq. State of California Department of Transportation, Division of Engineering Services, Materials Engineering, and Testing Services, Corrosion Technology Branch, 2003, Corrosion Guidelines, Version 1.0, dated September. Tan, S.S., and Giffen, D.G., 1995, Landslide hazards in the northern part of the San Diego Metropolitan area, San Diego County, California, Landslide hazard identification map no. 35, Plate 35G, Department of Conservation, Division of Mines and Geology, DMG Open File Report 95-04. United States Geological Survey, 2014, U.S. Seismic design maps, earthquake hazards program, http://geohazards.usgs.gov/designmaps/us/application.php. Version 3.1.0, dated July. Ron Ozaki Appendix A FiIe:e:\wp12\7000\7014a.pge eoSo*Is, Inc. Page 2 APPENDIX B HAND AUGER BORING LOGS Geooils, Inc. UNIFIED SOIL CLASSIFICATION SYSTEM CONSISTENCY OR RELATIVE DENSITY Major Divisions Group Symbols Typical Names CRITERIA Well-graded gravels and gravel- GW sand mixtures, little or no lines Standard Penetration Test 'I' o Poorly graded gravels and Penetration GP gravel-sand mixtures, little or no Resistance N Relative E Z fines (blows/It) Density 9: 5) GM Silty gravels gravel-sand-silt 0-4 Very loose oz ("C g ____ mixtures ____________ 4-10 Loose 0 69 GC Clayey gravels, gravel-sand-clay C mixtures 10-30 Medium SW Well-graded sands and gravelly 30 -50 Dense 59 sands, little or no fines C (5 5) Q)C >50 Verydense U' Poorly graded sands and gravelly sands, little or no fines 0 SM Silty sands, sand-silt mixtures m o8 E Cc Clayey sands, sand-clay SC mixtures Inorganic silts, very fine sands, Standard Penetration Teat ML rock flour, silty or clayey fine sands 5) . . Unconfined Penetration Compressive Inorganic clays of low to o 0 CL medium plasticity, gravelly clays, Resistance N Strength (11 0.9: sandy clays, silty clays, lean (blows/It) Consistency (tons/ft2) U' 2 clays Organic silts and organic silty <2 Very Soft <0.25 C U3 OL clays of low plasticity 2 -4 Soft 0.25 -.050 CD C 0 aR MH Inorganic silts, micaceous or diatomaceous fine sands or silts, 4 -8 Medium 0.50 -1.00 elastic silts o 815 Stiff 1.002.00 Inorganic clays 01 high plasticity, 0 clays 15-30 Very Stiff 2.00-4.00 16 LPT CH fat Organic clays of medium to high >30 Hard >4.00 plasticity rganic Soils Peat, mucic, and other highly organic soils 3 3/4U #4 #10 #40 #200 U.S. Standard Sieve Soil I Gravel I Sand Silt or Clay I Unified Classification Cobbles 111 f coarse I fine coarse I medium fine MOISTURE CONDITIONS MATERIAL QUANTITY OTHER SYMBOLS Dry Absence of moisture: dusty, dry to the touch trace 0-5% C Core Sample Slightly Moist Below optimum moisture content for compaction few 5-10% S SPT Sample Moist Near optimum moisture content little 10-25% B Bulk Sample Very Moist Above optimum moisture content some 25-45% Groundwater Wet Visible free water; below water table Op Pocket Penetrometer BASIC LOG FORMAT: Group name, Group symbol, (grain size), color, moisture, consistency or relative density. Additional comments: odor, presence of roots, mica, gypsum, coarse grained particles, etc. EXAMPLE: Sand (SP), fine to medium grained, brown, moist, loose, trace silt, little fine gravel, few cobbles up to 4" in size, some hair roots and rootlets. Filo:Mgr: c;\SoilClassif.wpd PLATE B-i 1417~ a W.O. 7014-A-SC Ozaki 1645 Chestnut, Carlsbad Logged By: ATS January 19, 2016 LOG OF EXPLORATORY HAND AUGER AUGER NO V V- '" DEHhGROUP -rnrmwn DEPTH DENSITY4 1Y4 DESCRIPTION HA-1 166 ½ 0-3 SM 1 COLLUVIUM: SILTY SAND, dark brown, moist, loose; medium to fine grained. 3 - 5 SM 3 - 5 OLD PARALIC DEPOSITS: SILTY SAND, light red yellowish brown, damp, medium dense; fine grained. Total Depth = 5 No Groundwater/Caving Encountered Backfilled 1/19/2016 HA-2 167 0- 21h SM 1 COLLUVIUM: SILTY SAND, dark brown, moist, loose; medium to fine grained. 21A - 4 SM 3 -4 OLD PARALIC DEPOSITS: SILTY SAND, light red yellowish brown, moist, medium dense; fine grained. Total Depth = 4' No Groundwater/Caving Encountered Backfilled 1/19/2016 HA-3 167 0- 1½ SM 1 COLLUVIUM: SILTY SAND, dark brown, moist, loose; medium to fine grained. 11A -5 SM 3-5 OLD PARALIC DEPOSITS: SILTY SAND, light red yellowish brown, moist, medium dense; fine grained. Total Depth = 5' - No Groundwater/Caving Encountered Backfilled 1/19/2016 PLATE B-2 APPENDIX C SEISMICITY GeoSoils, Inc. 7014EQF . OUT * *** ** * * * ** *** ** * * * * * ** * * * E Q F A U L T * * * * Version 3.00 * * * ** ** * ** * *** *** *** * ** * ** DETERMINISTIC ESTIMATION OF PEAK ACCELERATION FROM DIGITIZED FAULTS JOB NUMBER: 7014-A-SC DATE: 01-27-2016 JOB NAME: Ozaki CALCULATION NAME: 7014 EQF FAULT-DATA-FILE NAME: C:\Program Fl 1 eS\EQFAULT1\CDMGFLTE .DAT SITE COORDINATES: SITE LATITUDE: 33.1609 SITE LONGITUDE: 117.3306 SEARCH RADIUS: 62.4 ml ATTENUATION RELATION: 11) Bozorgnia Campbell Niazi (1999) Hor.-Pleist. Soil-Cor. UNCERTAINTY (M=Median, S=Sigma): S Number of Sigmas: 1.0 DISTANCE MEASURE: cdist SCOND: 1 Basement Depth: .01 km Campbell SSR: 0 Campbell SHR: 0 COMPUTE PEAK HORIZONTAL ACCELERATION FAULT-DATA FILE USED: C:\Program Files\EQFAULT1\CDMGFLTE.DAT MINIMUM DEPTH VALUE (km): 3.0 Page 1 W.O. 7014-A-SC PLATE C-I 7014 EQF . OUT --------------- EQFAULT SUMMARY --------------- ----------------------------- DETERMINISTIC SITE PARAMETERS ----------------------------- Page 1 ABBREVIATED I FAULT NAME I APPROXIMATE DISTANCE ml (km) 1 5.8( 9.3)1 ESTIMATED MAX. MAXIMUM I JEARTHQUAKE1 MAG.(MW) 6.9 EARTHQUAKE PEAK SITE ACCEL. g 0.526 EVENT EST. SITE INTENSITY IMOD.MERC. x ROSE CANYON NEWPORT-INGLEWOOD (Offshore) 1 6.0( 9.7)1 6.9 0.512 X CORONADO BANK 21.7( 35.0) 7.4 0.232 IX ELSINORE-TEMECULA 23.5( 37.9) 6.8 0.144 VIII ELSINORE-JULIAN 23.7( 38.2) 7.1 0.174 VIII ELSINORE-GLEN IVY 33.4( 53.7) 6.8 0.100 VII PALOS VERDES 36.2( 58.3) 7.1 1 0.113 VII EARTHQUAKE VALLEY 43.4( 69.8) 6.5 0.062 vi SAN JACINTO-ANZA 46.1( 74.2) 7.2 0.094 VII NEWPORT-INGLEWOOD (L.A.Basin) 1 46.2( 74.3) 6.9 0.076 VII SAN JACINTO-SAN JACINTO VALLEY 1 46.7( 75.1) 6.9 0.075 VII CHINO-CENTRAL AVE. (Elsinore) 47.6( 76.6) 6.7 0.091 VII WHITTIER 51.1( 82.2) 6.8 0.064 VI SAN JACINTO-COYOTE CREEK 51.8( 83.4) 6.8 0.063 VI COMPTON THRUST 55.9( 89.9) 6.8 0.083 VII ELSINORE-COYOTE MOUNTAIN 57.7( 92.8) 6.8 0.056 VI ELYSIAN PARK THRUST 58.7( 94.4) 6.7 0.073 VII SAN )ACINTO-SAN BERNARDINO 59.3( 95.5) 6.7 0.051 1 VI -END OF SEARCH- 18 FAULTS FOUND WITHIN THE SPECIFIED SEARCH RADIUS. THE ROSE CANYON FAULT IS CLOSEST TO THE SITE. IT IS ABOUT 5.8 MILES (9.3 km) AWAY. LARGEST MAXIMUM-EARTHQUAKE SITE ACCELERATION: 0.5262 g Page 2 W.O. 7014-A-SC PLATE C-2 7.4 7.3 7.2 7.1 6.7 6.5 EARTHQUAKE MAGNITUDES & DISTANCES Ozaki .1 1 10 Distance (mi) W.O. 7014.A-SC PLATE C.8 7014-EQS .OUT ** * * * * * ** ** * ** ** *** * * * * * E Q S E A R C H * * * * Version 3.00 * * * ** *** * ** *** * * ** ** * *** * *** ESTIMATION OF PEAK ACCELERATION FROM CALIFORNIA EARTHQUAKE CATALOGS JOB NUMBER: 7014-A-Sc DATE: 01-27-2016 JOB NAME: Ozaki EARTHQUAKE-CATALOG-FILE NAME: C:\Program Fi 1 eS\EQSEARCH\ALLQUAKE. DAT MAGNITUDE RANGE: MINIMUM MAGNITUDE: 5.00 MAXIMUM MAGNITUDE: 9.00 SITE COORDINATES: SITE LATITUDE: 33.1609 SITE LONGITUDE: 117.3306 SEARCH DATES: START DATE: 1800 END DATE: 2016 SEARCH RADIUS: 62.4 ml 100.4 km ATTENUATION RELATION: 11) Bozorgnia Campbell Niazi (1999) Hor.-Pleist. Soil-Cor. UNCERTAINTY (M=Median, S=Slgma): S Number of Sigmas: 1.0 ASSUMED SOURCE TYPE: SS [SS=Strike-slip, DS=Reverse-slip, BT=Blind-thrust] SCOND: 1 Depth Source: A Basement Depth: .01 km Campbell SSR: 0 Campbell SHR: 0 COMPUTE PEAK HORIZONTAL ACCELERATION MINIMUM DEPTH VALUE (km): 3.0 Page 1 W.O. 7014-A-SC PLATE C-9 7014-EQS .OUT ------------------------- EARTHQUAKE SEARCH RESULTS ------------------------- Page 1 I I I TIME I I SITE ISITEl APPROX. FILEI LAT. I LONG. DATE (uTc) DEPTH QUAKEI ACC. MM I DISTANCE CODEI NORTH I WEST I I H M Sec (km) MAG.I g INT. mi [km] ----+-------+--------+----------+--------+-----+-----+-------+----+------------ DMG 133.00001117.3000111/22/180012130 0.01 0.01 6.501 0.244 I IX I 11.2( 18.1) MGI 330000 117.0000 09/21/1856 730 0.0 0.0 5.00 0.050 VI 22.1( 35.6) MGI 132:80001117.1000105/25/18031 0 0 0.0 0.0 5.00 0.039 V 28.3( 45.5) DMG 132.70001117.2000105/27/1862120 0 0.01 0.01 5.901 0.057 I VI 32.7( 52.6) PAS 132.97101117.8700107/13/198611347 8.21 6.01 5.301 0.038 I V 33.8( 54.5) T-A 3267001 117.1700112/00/18561 0 0 0.0 0.0 5.00 0.031 I V 35.1( 56.6) 1-A 132:6700 117.1700110/21/1862 0 0 0.0 0.0 5.00 0.031 V 35.1( 56.6) T-A 132.6700 117.1700105/24/18651 0 0 0.01 0.01 5.00 0.031 V I 35.1( 56.6) DMG 33.2000 116.7000 01/01/19201 235 0.0 0.0 5.00 0.030 I V 36.5( 58.8) DMG 33.7000 117.4000 05/13/1910 620 0.0 0.0 5.00 0.029 I V 37.4( 60.2) DMG 133.7000 117.4000104/11/1910 757 0.01 0.01 5.001 0.029 V I 37.4( 60.2) DMG 1 33.70001 117.4000105/15/191011547 0.01 0.01 6.001 0.053 VI I 37.4( 60.2) DMG 33.69901117.5110105/31/19381 83455.4 10.0 5.50 0.037 V 38.6( 62.1) DMG 32.80001116.8000110/23/1894123 3 0.0 0.0 5.70 0.041 V 39.6( 63.7) MGI 133.20001116.6000 10/12/1920 1748 0.0 0.0 5.30 0.030 I V 42.3( 68.1) DMG 133.71001116.9250 09/23/1963 144152.6 16.5 5.00 0.024 I V I 44.5( 71.7) DMG 337500 117.0000 04/21/1918 223225.0 0.0 6.80 0.073 VIII 44.9( 72.3) DMG 133:7500 117.0000 06/06/1918 2232 0.0 0.0 5.00 0.024 IV I 44.9( 72.3) MGI 133.80001117.6000104/22/191812115 0.0 0.01 5.001 0.023 I IV I 46.8( 75.3) DMG 33.5750 117.9830103/11/19331 518 4.01 0.01 5.20 0.025 V 47.2( 76.0) DMG 33.8000 117.0000112/25/189911225 0.01 0.01 6.401 0.052 VI 48.1( 77.3) DMG 1 33.61701117.9670103/11/19331 154 7.81 0.01 6.30 0.049 VI I 48.3( 77.8) DMG 33.61701118.0170103/14/1933119 150.01 0.01 5.10 0.022 I IV I 50.6( 81.4) DMG 133.90001117.2000112/19/1880 0 0 0.0 0.0 6.00 0.037 I V 51.6( 83.0) PAS 33.5010 116.5130 02/25/1980 104738.5 13.6 5.50 0.027 V 1 52.7( 84.8) POP 133.50801116.5140 10/31/20011075616.61 15.01 5.101 0.021 IV I 52.8( 85.0) DMG 1 33.00001116.4330 06/04/1940 1035 8.3 0.0 5.10 0.021 I IV I 53.1( 85.5) DMG 33.50001116.5000 09/30/1916 211 0.0 0.0 5.00 0.020 IV I 53.3( 85.8) DMG 133.68301118.0500 03/11/19331 658 3.01 0.0 5.501 0.026 V I 54.9( 88.4) DMG I33.70001118.0670103/Uh1933 85457.0 0.0 5.10 0.020 Iv I 56.4( 90.8) DMG 33.7000 118.0670 03/11/1933 51022.0 0.0 5.10 0.020 IV 56.4( 90.8) DMG 34.0000 117.2500 07/23/1923 73026.0 0.0 6.25 0.039 V 58.1( 93.5) DMG 133.3430 116.3460 04/28/1969 232042.91 20.01 5.80 0.029 I V 58.2( 93.7) MGI 134.00001 117.5000112/16/1858 10 0 0.0 0.0 7.00 0.063 I VI 58.7( 94.5) DMG 133.7500 118.0830 03/11/1933 323 0.0 0.0 5.00 0.018 IV 59.4( 95.6) DMG 33.7500 118.0830 03/11/1933 230 0.0 0.0 5.10 0.019 IV 59.4( 95.6) DMG 133.7500 118.0830103/13/1933 131828.0 0.0 5.30 0.021 IV I 59.4( 95.6) DMG 133.7500 118.0830103/11/19331 910 0.01 0.01 5.101 0.019 Iv 59.4( 95.6) DMG 133.7500 118.0830 03/11/19331 2 9 0.01 0.0 5.001 0.018 IV 59.4( 95.6) DMG 133.95001116.8500109/28/19461 719 9.01 0.0 5.001 0.017 I Iv 61.1( 98.3) DMG 133.40001116.3000 02/09/1890112 6 0.01 0.01 6.301 0.038 I V 61.7( 99.3) Page 2 W.O. 7014-A-SC PLATE C-b 7014-EQS .OUT -END OF SEARCH- 41 EARTHQUAKES FOUND WITHIN THE SPECIFIED SEARCH AREA. TIME PERIOD OF SEARCH: 1800 TO 2016 LENGTH OF SEARCH TIME: 217 years THE EARTHQUAKE CLOSEST TO THE SITE IS ABOUT 11.2 MILES (18.1 km) AWAY. LARGEST EARTHQUAKE MAGNITUDE FOUND IN THE SEARCH RADIUS: 7.0 LARGEST EARTHQUAKE SITE ACCELERATION FROM THIS SEARCH: 0.244 g COEFFICIENTS FOR GUTENBERG & RICHTER RECURRENCE RELATION: a-value= 0.811 b-value= 0.351 beta-value= 0.808 ------------------------------------ TABLE OF MAGNITUDES AND EXCEEDANCES: ------------------------------------ Earthquake Number of Times I I Cumulative Magnitude Exceeded I No. / Year +-----------------+------------ 4.0 41 I 0.18894 4.5 41 0.18894 5.0 41 0.18894 5.5 15 0.06912 6.0 9 I 0.04147 6.5 3 0.01382 7.0 1 0.00461 Page 3 W.O. 7014-A-SC PLATE C-Il APPENDIX D GENERAL EARTHWORK AND GRADING GUIDELINES Geo$oils, Inc. GENERAL EARTHWORK AND GRADING GUIDELINES General These guidelines present general procedures and requirements for earthwork and grading as shown on the approved grading plans, including preparation of areas to be filled, placement of fill, installation of subdrains, excavations, and appurtenant structures or flatwork. The recommendations contained in the geotechnical report are part of these earthwork and grading guidelines and would supercede the provisions contained hereafter in the case of conflict. Evaluations performed by the consultant during the course of grading may result in new or revised recommendations which could supercede these guidelines or the recommendations contained in the geotechnical report. Generalized details follow this text. The contractor is responsible for the satisfactory completion of all earthwork in accordance with provisions of the project plans and specifications and latest adopted code. In the case of conflict, the most onerous provisions shall prevail. The project geotechnical engineer and engineering geologist (geotechnical consultant), and/or their representatives, should provide observation and testing services, and geotechnical consultation during the duration of the project. EARTHWORK OBSERVATIONS AND TESTING Geotechnical Consultant Prior to the commencement of grading, a qualified geotechnical consultant (soil engineer and engineering geologist) should be employed for the purpose of observing earthwork procedures and testing the fills for general conformance with the recommendations of the geotechnical report(s), the approved grading plans, and applicable grading codes and ordinances. The geotechnical consultant should provide testing and observation so that an evaluation may be made that the work is being accomplished as specified. It is the responsibility of the contractor to assist the consultants and keep them apprised of anticipated work schedules and changes, so that they may schedule their personnel accordingly. All remedial removals, clean-outs, prepared ground to receive fill, key excavations, and subdrain installation should be observed and documented by the geotechnical consultant prior to placing any fill. It is the contractor's responsibility to notify the geotechnical consultant when such areas are ready for observation. Laboratory and Field Tests Maximum dry density tests to determine the degree of compaction should be performed in accordance with American Standard Testing Materials test method ASTM designation D-1557. Random or representative field compaction tests should be performed in GeoSoils, Inc. accordance with test methods ASTM designation 0-1556, D-2937 or D-2922, and D-3017, at intervals of approximately ±2 feet of fill height or approximately every 1,000 cubic yards placed. These criteria would vary depending on the soil conditions and the size of the project. The location and frequency of testing would be at the discretion of the geotechnical consultant. Contractor's Responsibility All clearing, site preparation, and earthwork performed on the project should be conducted by the contractor, with observation by a geotechnical consultant, and staged approval by the governing agencies, as applicable. It is the contractor's responsibility to prepare the ground surface to receive the fill, to the satisfaction of the geotechnical consultant, and to place, spread, moisture condition, mix, and compact the fill in accordance with the recommendations of the geotechnical consultant. The contractor should also remove all non-earth material considered unsatisfactory by the geotechnical consultant. Notwithstanding the services provided by the geotechnical consultant, it is the sole responsibility of the contractorto provide adequate equipment and methods to accomplish the earthwork in strict accordance with applicable grading guidelines, latest adopted codes or agency ordinances, geotechnical report(s), and approved grading plans. Sufficient watering apparatus and compaction equipment should be provided by the contractor with due consideration for the fill material, rate of placement, and climatic conditions. If, in the opinion of the geotechnical consultant, unsatisfactory conditions such as questionable weather, excessive oversized rock or deleterious material, insufficient support equipment, etc., are resulting in a quality of work that is not acceptable, the consultant will inform the contractor, and the contractor is expected to rectify the conditions, and if necessary, stop work until conditions are satisfactory. During construction, the contractor shall properly grade all surfaces to maintain good drainage and prevent ponding of water. The contractor shall take remedial measures to control surface water and to prevent erosion of graded areas until such time as permanent drainage and erosion control measures have been installed. SITE PREPARATION All major vegetation, including brush, trees, thick grasses, organic debris, and other deleterious material, should be removed and disposed of off-site. These removals must be concluded prior to placing fill. In-place existing fill, soil, alluvium, colluvium, or rock materials, as evaluated by the geotechnical consultant as being unsuitable, should be removed prior to any fill placement. Depending upon the soil conditions, these materials may be reused as compacted fills. Any materials incorporated as part of the compacted fills should be approved by the geotechnical consultant. Any underground structures such as cesspools, cisterns, mining shafts, tunnels, septic tanks, wells, pipelines, or other structures not located prior to grading, are to be removed Ron Ozaki Appendix D FiIe:e:\wp12\7000\7014a.pge GeOSOUS9 Inc. Page 2 or treated in a manner recommended by the geotechnical consultant. Soft, dry, spongy, highly fractured, or otherwise unsuitable ground, extending to such a depth that surface processing cannot adequately improve the condition, should be overexcavated down to firm ground and approved by the geotechnical consultant before compaction and filling operations continue. Overexcavated and processed soils, which have been properly mixed and moisture conditioned, should be re-compacted to the minimum relative compaction as specified in these guidelines. Existing ground, which is determined to be satisfactory for support of the fills, should be scarified (ripped) to a minimum depth of 6 to 8 inches, or as directed by the geotechnical consultant. After the scarified ground is brought to optimum moisture content, or greater and mixed, the materials should be compacted as specified herein. If the scarified zone is greater than 6 to 8 inches in depth, it may be necessary to remove the excess and place the material in lifts restricted to about 6 to 8 inches in compacted thickness. Existing ground which is not satisfactory to support compacted fill should be overexcavated as required in the geotechnical report, or by the on-site geotechnical consultant. Scarification, disc harrowing, or other acceptable forms of mixing should continue until the soils are broken down and free of large lumps or clods, until the working surface is reasonably uniform and free from ruts, hollows, hummocks, mounds, or other uneven features, which would inhibit compaction as described previously. Where fills are to be placed on ground with slopes steeper than 5:1 (horizontal to vertical [h:v]), the ground should be stepped or benched. The lowest bench, which will act as a key, should be a minimum of 15 feet wide and should be at least 2 feet deep into firm material, and approved by the geotechnical consultant. In fill-over-cut slope conditions, the recommended minimum width of the lowest bench or key is also 15 feet, with the key founded on firm material, as designated by the geotechnical consultant. As a general rule, unless specifically recommended otherwise by the geotechnical consultant, the minimum width of fill keys should be equal to 1/2 the height of the slope. Standard benching is generally 4 feet (minimum) vertically, exposing firm, acceptable material. Benching may be used to remove unsuitable materials, although it is understood that the vertical height of the bench may exceed 4 feet. Pre-stripping may be considered for unsuitable materials in excess of 4 feet in thickness. All areas to receive fill, including processed areas, removal areas, and the toes of fill benches, should be observed and approved by the geotechnical consultant prior to placement of fill. Fills may then be properly placed and compacted until design grades (elevations) are attained. COMPACTED FILLS Any earth materials imported or excavated on the property may be utilized in the fill provided that each material has been evaluated to be suitable by the geotechnical Ron Ozaki Appendix 0 FlIe:e:\wp12\7000\7014a.pge OSOilS, Inc. Page 3 consultant. These materials should be free of roots, tree branches, other organic matter, or other deleterious materials. All unsuitable materials should be removed from the fill as directed by the geotechnical consultant. Soils of poor gradation, undesirable expansion potential, or substandard strength characteristics may be designated by the consultant as unsuitable and may require blending with other soils to serve as a satisfactory fill material. Fill materials derived from benching operations should be dispersed throughout the fill area and blended with other approved material. Benching operations should not result in the benched material being placed only within a single equipment width away from the fill/bedrock contact. Oversized materials defined as rock, or other irreducible materials, with a maximum dimension greater than 12 inches, should not be buried or placed in fills unless the location of materials and disposal methods are specifically approved by the geotechnical consultant. Oversized material should be taken offsite, or placed in accordance with recommendations of the geotechnical consultant in areas designated as suitable for rock disposal. GSI anticipates that soils to be utilized as fill material for the subject project may contain some rock. Appropriately, the need for rock disposal may be necessary during grading operations on the site. From a geotechnical standpoint, the depth of any rocks, rock fills, or rock blankets, should be a sufficient distance from finish grade. This depth is generally the same as any overexcavation due to cut-fill transitions in hard rock areas, and generally facilitates the excavation of structural footings and substructures. Should deeper excavations be proposed (i.e., deepened footings, utility trenching, swimming pools, spas, etc.), the developer may consider increasing the hold-down depth of any rocky fills to be placed, as appropriate. In addition, some agencies/jurisdictions mandate a specific hold-down depth for oversize materials placed in fills. The hold-down depth, and potential to encounter oversize rock, both within fills, and occurring in cut or natural areas, would need to be disclosed to all interested/affected parties. Once approved by the governing agency, the hold-down depth for oversized rock (i.e., greater than 12 inches) in fills on this project is provided as 10 feet, unless specified differently in the text of this report. The governing agency may require that these materials need to be deeper, crushed, or reduced to less than 12 inches in maximum dimension, at their discretion. To facilitate future trenching, rock (or oversized material), should not be placed within the hold-down depth feetfrom finish grade, the range of foundation excavations, future utilities, or underground construction unless specifically approved by the governing agency, the geotechnical consultant, and/or the developer's representative. If import material is required for grading, representative samples of the materials to be utilized as compacted fill should be analyzed in the laboratory by the geotechnical consultant to evaluate it's physical properties and suitability for use onsite. Such testing should be performed three (3) days prior to importation. If any material other than that previously tested is encountered during grading, an appropriate analysis of this material should be conducted by the geotechnical consultant as soon as possible. Ron Ozaki Appendix 0 Fi1e:e:\wp12\7000\7014a.pge GeoSoUs,Inc. Page 4 Approved fill material should be placed in areas prepared to receive fill in near horizontal layers, that when compacted, should not exceed about 6 to 8 inches in thickness. The geotechnical consultant may approve thick lifts if testing indicates the grading procedures are such that adequate compaction is being achieved with lifts of greater thickness. Each layer should be spread evenly and blended to attain uniformity of material and moisture suitable for compaction. Fill layers at a moisture content less than optimum should be watered and mixed, and wet fill layers should be aerated by scarification, or should be blended with drier material. Moisture conditioning, blending, and mixing of the fill layer should continue until the fill materials have a uniform moisture content at, or above, optimum moisture. After each layer has been evenly spread, moisture conditioned, and mixed, it should be uniformly compacted to a minimum of 90 percent of the maximum density as evaluated by ASTM test designation D-1557, or as otherwise recommended by the geotechnical consultant. Compaction equipment should be adequately sized and should be specifically designed for soil compaction, or of proven reliability to efficiently achieve the specified degree of compaction. Where tests indicate that the density of any layer of fill, or portion thereof, is below the required relative compaction, or improper moisture is in evidence, the particular layer or portion shall be re-worked until the required density and/or moisture content has been attained. No additional fill shall be placed in an area until the last placed lift of fill has been tested and found to meet the density and moisture requirements, and is approved by the geotechnical consultant. In general, per the latest adopted version of the California Building Code (CBC), fill slopes should be designed and constructed at a gradient of 2:1 (h:v), or flatter. Compaction of slopes should be accomplished by over-building a minimum of 3 feet horizontally, and subsequently trimming back to the design slope configuration. Testing shall be performed as the fill is elevated to evaluate compaction as the fill core is being developed. Special efforts may be necessary to attain the specified compaction in the fill slope zone. Final slope shaping should be performed by trimming and removing loose materials with appropriate equipment. A final evaluation of fill slope compaction should be based on observation and/or testing of the finished slope face. Where compacted fill slopes are designed steeper than 2:1 (h:v), prior approval from the governing agency, specific material types, a higher minimum relative compaction, special reinforcement, and special grading procedures will be recommended. If an alternative to over-building and cutting back the compacted fill slopes is selected, then special effort should be made to achieve the required compaction in the outer 10 feet of each lift of fill by undertaking the following: An extra piece of equipment consisting of a heavy, short-shanked sheepsfoot should be used to roll (horizontal) parallel to the slopes continuously as fill is placed. The sheepsfoot roller should also be used to roll perpendicular to the Ron Ozaki Appendix 0 Fi1e:e:\wp12\7000\7014a.pge GOSoi1S, Inc. Page 5 slopes, and extend out over the slope to provide adequate compaction to the face of the slope. Loose fill should not be spilled out over the face of the slope as each lift is compacted. Any loose fill spilled over a previously completed slope face should be trimmed oft or be subject to re-rolling. Field compaction tests will be made in the outer (horizontal) ±2 to ±8 feet of the slope at appropriate vertical intervals, subsequent to compaction operations. After completion of the slope, the slope face should be shaped with a small tractor and then re-rolled with a sheepsfoot to achieve compaction to near the slope face. Subsequent to testing to evaluate compaction, the slopes should be grid-rolled to achieve compaction to the slope face. Final testing should be used to evaluate compaction after grid rolling. Where testing indicates less than adequate compaction, the contractor will be responsible to rip, water, mix, and recompact the slope material as necessary to achieve compaction. Additional testing should be performed to evaluate compaction. SUBDRAIN INSTALLATION Subdrains should be installed in approved ground in accordance with the approximate alignment and details indicated by the geotechnical consultant. Subdrain locations or materials should not be changed or modified without approval of the geotechnical consultant. The geotechnical consultant may recommend and direct changes in subdrain line, grade, and drain material in the field, pending exposed conditions. The location of constructed subdrains, especially the outlets, should be recorded/surveyed by the project civil engineer. Drainage at the subdrain outlets should be provided by the project civil engineer. EXCAVATIONS Excavations and cut slopes should be examined during grading by the geotechnical consultant. If directed by the geotechnical consultant, further excavations or overexcavation and refilling of cut areas should be performed, and/or remedial grading of cut slopes should be performed. When fill-over-cut slopes are to be graded, unless otherwise approved, the cut portion of the slope should be observed by the geotechnical consultant prior to placement of materials for construction of the fill portion of the slope. The geotechnical consultant should observe all cut slopes, and should be notified by the contractor when excavation of cut slopes commence. Ron Ozaki Appendix D FiIe:e:\wp12\7000\7014a.pge Ge0S0u1s, Inc. Page 6 If, during the course of grading, unforeseen adverse or potentially adverse geologic conditions are encountered, the geotechnical consultant should investigate, evaluate, and make appropriate recommendations for mitigation of these conditions. The need for cut slope buttressing or stabilizing should be based on in-grading evaluation by the geotechnical consultant, whether anticipated or not. Unless otherwise specified in geotechnical and geological report(s), no cut slopes should be excavated higher or steeper than that allowed by the ordinances of controlling governmental agencies. Additionally, short-term stability of temporary cut slopes is the contractor's responsibility. Erosion control and drainage devices should be designed by the project civil engineer and should be constructed in compliance with the ordinances of the controlling governmental agencies, and/or in accordance with the recommendations of the geotechnical consultant. COMPLETION Observation, testing, and consultation by the geotechnical consultant should be conducted during the grading operations in order to state an opinion that all cut and fill areas are graded in accordance with the approved project specifications. After completion of grading, and after the geotechnical consultant has finished observations of the work, final reports should be submitted, and may be subject to review by the controlling governmental agencies. No further excavation or filling should be undertaken without prior notification of the geotechnical consultant or approved plans. All finished cut and fill slopes should be protected from erosion and/or be planted in accordance with the project specifications and/or as recommended by a landscape architect. Such protection and/or planning should be undertaken as soon as practical after completion of grading. PRELIMINARY OUTDOOR POOL/SPA DESIGN RECOMMENDATIONS The following preliminary recommendations are provided for consideration in pool/spa design and planning. Actual recommendations should be provided by a qualified geotechnical consultant, based on site specific geotechnical conditions, including a subsurface investigation, differential settlement potential, expansive and corrosive soil potential, proximity of the proposed pool/spa to any slopes with regard to slope creep and lateral fill extension, as well as slope setbacks per Code, and geometry of the proposed improvements. Recommendations for pools/spas and/or deck flatwork underlain by expansive soils, or for areas with differential settlement greater than ¼-inch over 40 feet horizontally, will be more onerous than the preliminary recommendations presented below. The 1:1 (h:v) influence zone of any nearby retaining wall site structures should be delineated on the project civil drawings with the pool/spa. This 1:1 (h:v) zone is defined Ron Ozaki Appendix D F11e:e:\wp12\7000\7014a.pge OSOi1S, Inc. Page 7 as a plane up from the lower-most heel of the retaining structure, to the daylight grade of the nearby building pad or slope. If pools/spas or associated pool/spa improvements are constructed within this zone, they should be re-positioned (horizontally or vertically) so that they are supported by earth materials that are outside or below this 1:1 plane. If this is not possible given the area of the building pad, the owner should consider eliminating these improvements or allow for increased potential for lateral/vertical deformations and associated distress that may render these improvements unusable in the future, unless they are periodically repaired and maintained. The conditions and recommendations presented herein should be disclosed to all homeowners and any interested/affected parties. General The equivalent fluid pressure to be used for the pool/spa design should be 60 pounds per cubic foot (pcf) for pool/spa walls with level backfill, and 75 pcf for a 2:1 sloped backfill condition. In addition, backdrains should be provided behind pool/spa walls subjacent to slopes. Passive earth pressure may be computed as an equivalent fluid having a density of 150 pcf, to a maximum lateral earth pressure of 1,000 pounds per square foot (psf). An allowable coefficient of friction between soil and concrete of 0.30 may be used with the dead load forces. When combining passive pressure and frictional resistance, the passive pressure component should be reduced by one-third. Where pools/spas are planned near structures, appropriate surcharge loads need to be incorporated into design and construction by the pool/spa designer. This includes, but is not limited to landscape berms, decorative walls, footings, built-in barbeques, utility poles, etc. All pool/spa walls should be designed as "free standing" and be capable of supporting the water in the pool/spa without soil support. The shape of pool/spa in cross section and plan view may affect the performance of the pool, from a geotechnical standpoint. Pools and spas should also be designed in accordance with the latest adopted Code. Minimally, the bottoms of the pools/spas, should maintain a distance H/3, where H is the height of the slope (in feet), from the slope face. This distance should not be less than 7 feet, nor need not be greater than 40 feet. The soil beneath the pool/spa bottom should be uniformly moist with the same stiffness throughout. If a fill/cut transition occurs beneath the pool/spa bottom, the cut portion should be overexcavated to a minimum depth of 48 inches, and replaced with compacted fill, such that there is a uniform blanket that is a minimum of 48 inches below the pool/spa shell. If very low expansive soil is used for fill, the Ron Ozaki Appendix D F1Ie:e:\wp12\7000\7014a.pge OSOdS, Inc. Page 8 fill should be placed at a minimum of 95 percent relative compaction, at optimum moisture conditions. This requirement should be 90 percent relative compaction at over optimum moisture if the pool/spa is constructed within or near expansive soils. The potential for grading and/or re-grading of the pool/spa bottom, and attendant potential for shoring and/or slot excavation, needs to be considered during all aspects of pool/spa planning, design, and construction. If the pool/spa is founded entirely in compacted fill placed during rough grading, the deepest portion of the pool/spa should correspond with the thickest fill on the lot. Hydrostatic pressure relief valves should be incorporated into the pool and spa designs. A pool/spa under-drain system is also recommended, with an appropriate outlet for discharge. All fittings and pipe joints, particularly fittings in the side of the pool or spa, should be properly sealed to prevent water from leaking into the adjacent soils materials, and be fitted with slip or expandible joints between connections transecting varying soil conditions. An elastic expansion joint (flexible waterproof sealant) should be installed to prevent water from seeping into the soil at all deck joints. A reinforced grade beam should be placed around skimmer inlets to provide support and mitigate cracking around the skimmer face. In order to reduce unsightly cracking, deck slabs should minimally be 4 inches thick, and reinforced with No. 3 reinforcing bars at 18 inches on-center. All slab reinforcement should be supported to ensure proper mid-slab positioning during the placement of concrete. Wire mesh reinforcing is specifically not recommended. Deck slabs should not be tied to the pool/spa structure. Pre-moistening and/or pre-soaking of the slab subgrade is recommended, to a depth of 12 inches (optimum moisture content), or 18 inches (120 percent of the soil's optimum moisture content, or 3 percent over optimum moisture content, whichever is greater), for very low to low, and medium expansive soils, respectively. This moisture content should be maintained in the subgrade soils during concrete placement to promote uniform curing of the concrete and minimize the development of unsightly shrinkage cracks. Slab underlayment should consist of a 1- to 2-inch leveling course of sand (S.E. >30) and a minimum of 4 to 6 inches of Class 2 base compacted to 90 percent. Deck slabs within the H/3 zone, where H is the height of the slope (in feet), will have an increased potential for distress relative to other areas outside of the H/3 zone. If distress is undesirable, improvements, deck slabs orflatwork should not be constructed closer than H/3 or 7 feet (whichever is greater) from the slope face, in order to reduce, but not eliminate, this potential. Ron Ozaki Appendix D Fi1e:e:\wp12\7000\7014a.pge GeoSoils, Inc. Page 9 Pool/spa bottom or deck slabs should be founded entirely on competent bedrock, or properly compacted fill. Fill should be compacted to achieve a minimum 90 percent relative compaction, as discussed above. Prior to pouring concrete, subgrade soils below the pool/spa decking should be throughly watered to achieve a moisture content that is at least 2 percent above optimum moisture content, to a depth of at least 18 inches below the bottom of slabs. This moisture content should be maintained in the subgrade soils during concrete placement to promote uniform curing of the concrete and minimize the development of unsightly shrinkage cracks. In order to reduce unsightly cracking, the outer edges of pool/spa decking to be bordered by landscaping, and the edges immediately adjacent to the pool/spa, should be underlain by an 8-inch wide concrete cutoff shoulder (thickened edge) extending to a depth of at least 12 inches below the bottoms of the slabs to mitigate excessive infiltration of water under the pool/spa deck. These thickened edges should be reinforced with two No. 4 bars, one at the top and one at the bottom. Deck slabs may be minimally reinforced with No. 3 reinforcing bars placed at 18 inches on-center, in both directions. All slab reinforcement should be supported on chairs to ensure proper mid-slab positioning during the placement of concrete. Surface and shrinkage cracking of the finish slab may be reduced if a low slump and water-cement ratio are maintained during concrete placement. Concrete utilized should have a minimum compressive strength of 4,000 psi. Excessive water added to concrete prior to placement is likely to cause shrinkage cracking, and should be avoided. Some concrete shrinkage cracking, however, is unavoidable. Joint and sawcut locations for the pool/spa deck should be determined by the design engineer and/or contractor. However, spacings should not exceed 6 feet on center. Considering the nature of the onsite earth materials, it should be anticipated that caving or sloughing could be a factor in subsurface excavations and trenching. Shoring or excavating the trench walls/backcuts at the angle of repose (typically 25 to 45 degrees), should be anticipated. All excavations should be observed by a representative of the geotechnical consultant, including the project geologist and/or geotechnical engineer, prior to workers entering the excavation or trench, and minimally conform to Cal/OSHA ("Type C" soils may be assumed), state, and local safety codes. Should adverse conditions exist, appropriate recommendations should be offered at that time by the geotechnical consultant. GSI does not consult in the area of safety engineering and the safety of the construction crew is the responsibility of the pool/spa builder. It is imperative that adequate provisions for surface drainage are incorporated by the homeowners into their overall improvement scheme. Ponding water, ground saturation and flow over slope faces, are all situations which must be avoided to enhance long term performance of the pool/spa and associated improvements, and reduce the likelihood of distress. Ron Ozaki Appendix D File:e:\wpl2\7000\7014a.pge GeOSOUS9 Inc. Page 10 Regardless of the methods employed, once the pool/spa is filled with water, should it be emptied, there exists some potential that if emptied, significant distress may occur. Accordingly, once filled, the pool/spa should not be emptied unless evaluated by the geotechnical consultant and the pool/spa builder. For pools/spas built within (all or part) of the Code setback and/or geotechnical setback, as indicated in the site geotechnical documents, special foundations are recommended to mitigate the affects of creep, lateral fill extension, expansive soils and settlement on the proposed pool/spa. Most municipalities or County reviewers do not consider these effects in pool/spa plan approvals. As such, where pools/spas are proposed on 20 feet or more of fill, medium or highly expansive soils, or rock fill with limited "cap soils" and built within Code setbacks, or within the influence of the creep zone, or lateral fill extension, the following should be considered during design and construction: OPTION A: Shallow foundations with or without overexcavation of the pool/spa "shell," such that the pool/spa is surrounded by 5 feet of very low to low expansive soils (without irreducible particles greater that 6 inches), and the pool/spa walls closer to the slope(s) are designed to be free standing. GSI recommends a pool/spa under-drain or blanket system (see attached Typical Pool/Spa Detail). The pool/spa builders and owner in this optional construction technique should be generally satisfied with pool/spa performance underthis scenario; however, some settlement, tilting, cracking, and leakage of the pool/spa is likely over the life of the project. OPTION B: Pier supported pool/spa foundations with or without overexcavation of the pool/spa shell such that the pool/spa is surrounded by 5 feet of very low to low expansive soils (without irreducible particles greater than 6 inches), and the pool/spa walls closer to the slope(s) are designed to be free standing. The need for a pool/spa under-drain system may be installed for leak detection purposes. Piers that support the pool/spa should be a minimum of 12 inches in diameter and at a spacing to provide vertical and lateral support of the pool/spa, in accordance with the pool/spa designers recommendations current applicable Codes. The pool/spa builder and owner in this second scenario construction technique should be more satisfied with pool/spa performance. This construction will reduce settlement and creep effects on the pool/spa; however, it will not eliminate these potentials, nor make the pool/spa "leak-free." The temperature of the water lines for spas and pools may affect the corrosion properties of site soils, thus, a corrosion specialist should be retained to review all spa and pool plans, and provide mitigative recommendations, as warranted. Concrete mix design should be reviewed by a qualified corrosion consultant and materials engineer. Ron Ozaki Appendix 0 Fi1e:e:\wp12\7000\7014a.p9e 0S01liI Inc. Page 11 All pool/spa utility trenches should be compacted to 90 percent of the laboratory standard, under the full-time observation and testing of a qualified geotechnical consultant. Utility trench bottoms should be sloped away from the primary structure on the property (typically the residence). Pool and spa utility lines should not cross the primary structure's utility lines (i.e., not stacked, or sharing of trenches, etc.). The pool/spa or associated utilities should not intercept, interrupt, or otherwise adversely impact any area drain, roof drain, or other drainage conveyances. If it is necessary to modify, move, or disrupt existing area drains, subdrains, or tightlines, then the design civil engineer should be consulted, and mitigative measures provided. Such measures should be further reviewed and approved by the geotechnical consultant, prior to proceeding with any further construction. The geotechnical consultant should review and approve all aspects of pool/spa and flatwork design prior to construction. A design civil engineer should review all aspects of such design, including drainage and setback conditions. Prior to acceptance of the pool/spa construction, the project builder, geotechnical consultant and civil designer should evaluate the performance of the area drains and other site drainage pipes, following pool/spa construction. All aspects of construction should be reviewed and approved by the geotechnical consultant, including during excavation, prior to the placement of any additional fill, prior to the placement of any reinforcement or pouring of any concrete. Any changes in design or location of the pool/spa should be reviewed and approved by the geotechnical and design civil engineer prior to construction. Field adjustments should not be allowed until written approval of the proposed field changes are obtained from the geotechnical and design civil engineer. Disclosure should be made to homeowners and builders, contractors, and any interested/affected parties, that pools/spas built within about 15 feet of the top of a slope, and/or H/3, where H is the height of the slope (in feet), will experience some movement or tilting. While the pool/spa shell or coping may not necessarily crack, the levelness of the pool/spa will likely tilt toward the slope, and may not be esthetically pleasing. The same is true with decking, flatwork and other improvements in this zone. Failure to adhere to the above recommendations will significantly increase the potential for distress to the pool/spa, flatwork, etc. Local seismicity and/or the design earthquake will cause some distress to the pool/spa and decking or flatwork, possibly including total functional and economic loss. Ron Ozaki Appendix D FIIe:e:\wp12\7000\7014a.pge Ge"oi1s, Inc. Page 12 32. The information and recommendations discussed above should be provided to any contractors and/or subcontractors, or homeowners, interested/affected parties, etc., that may perform or may be affected by such work. JOB SAFETY General At GSI, getting the job done safely is of primary concern. The following is the company's safety considerations for use by all employees on multi-employer construction sites. On-ground personnel are at highest risk of injury, and possible fatality, on grading and construction projects. GSI recognizes that construction activities will vary on each site, and that site safety is the prime responsibility of the contractor; however, everyone must be safety conscious and responsible at all times. To achieve our goal of avoiding accidents, cooperation between the client, the contractor, and GSI personnel must be maintained. In an effort to minimize risks associated with geotechnical testing and observation, the following precautions are to be implemented for the safety of field personnel on grading and construction projects: Safety Meetings: GSI field personnel are directed to attend contractor's regularly scheduled and documented safety meetings. Safety Vests: Safety vests are provided for, and are to be worn by GSI personnel, at all times, when they are working in the field. Safety Flags: Two safety flags are provided to GSI field technicians; one is to be affixed to the vehicle when on site, the other is to be placed atop the spoil pile on all test pits. Flashing Lights: All vehicles stationary in the grading area shall use rotating or flashing amber beacons, or strobe lights, on the vehicle during all field testing. While operating a vehicle in the grading area, the emergency flasher on the vehicle shall be activated. In the event that the contractor's representative observes any of our personnel not following the above, we request that it be brought to the attention of our office. Test Pits Location, Orientation, and Clearance The technician is responsible for selecting test pit locations. A primary concern should be the technician's safety. Efforts will be made to coordinate locations with the grading contractor's authorized representative, and to select locations following or behind the established traffic pattern, preferably outside of current traffic. The contractor's authorized representative (supervisor, grade checker, dump man, operator, etc.) should direct Ron Ozaki Appendix D FiIe:e:\wpl2\7000\7014a.pge GeeSoUs,Inc. Page 13 excavation of the pit and safety during the test period. Of paramount concern should be the soil technician's safety, and obtaining enough tests to represent the fill. Test pits should be excavated so that the spoil pile is placed away from oncoming traffic, whenever possible. The technician's vehicle is to be placed next to the test pit, opposite the spoil pile. This necessitates the fill be maintained in a driveable condition. Alternatively, the contractor may wish to park a piece of equipment in front of the test holes, particularly in small fill areas or those with limited access. A zone of non-encroachment should be established for all test pits. No grading equipment should enter this zone during the testing procedure. The zone should extend approximately 50 feet outward from the center of the test pit. This zone is established for safety and to avoid excessive ground vibration, which typically decreases test results. When taking slope tests, the technician should park the vehicle directly above or belowthe test location. If this is not possible, a prominent flag should be placed at the top of the slope. The contractors representative should effectively keep all equipment at a safe operational distance (e.g., 50 feet) away from the slope during this testing. The technician is directed to withdraw from the active portion of the fill as soon as possible following testing. The technician's vehicle should be parked at the perimeter of the fill in a highly visible location, well away from the equipment traffic pattern. The contractor should inform our personnel of all changes to haul roads, cut and fill areas or other factors that may affect site access and site safety. In the event that the technician's safety is jeopardized or compromised as a result of the contractor's failure to comply with any of the above, the technician is required, by company policy, to immediately withdraw and notify his/her supervisor. The grading contractor's representative will be contacted in an effort to affect a solution. However, in the interim, no further testing will be performed until the situation is rectified. Any fill placed can be considered unacceptable and subject to reprocessing, recompaction, or removal. In the event that the soil technician does not comply with the above or other established safety guidelines, we request that the contractor bring this to the technician's attention and notify this office. Effective communication and coordination between the contractor's representative and the soil technician is strongly encouraged in order to implement the above safety plan. Trench and Vertical Excavation It is the contractor's responsibility to provide safe access into trenches where compaction testing is needed. Our personnel are directed not to enter any excavation or vertical cut which: 1) is 5 feet or deeper unless shored or laid back; 2) displays any evidence of instability, has any loose rock or other debris which could fall into the trench; or 3) displays any other evidence of any unsafe conditions regardless of depth. Ron Ozaki Appendix D F1Ie:e:\wp12\7000\7014a.pge GeoSoils, Inc. Page 14 All trench excavations or vertical cuts in excess of 5 feet deep, which any person enters, should be shored or laid back. Trench access should be provided in accordance with Cal/OSHA and/or state and local standards. Our personnel are directed not to enter any trench by being lowered or "riding down" on the equipment. If the contractor fails to provide safe access to trenches for compaction testing, our company policy requires that the soil technician withdraw and notify his/her supervisor. The contractor's representative will be contacted in an effort to affect a solution. All backfill not tested due to safety concerns or other reasons could be subject to reprocessing and/or removal. If GSI personnel become aware of anyone working beneath an unsafe trench wall or vertical excavation, we have a legal obligation to put the contractor and owner/developer on notice to immediately correct the situation. If corrective steps are not taken, GSI then has an obligation to notify Cal/OSHA and/or the proper controlling authorities. Ron Ozaki Appendix D File:e:\wpl2\7000\7014a.pge Geoftilsq Inc. Page 15