GEOLOGIC HAZARDS ASSESSMENT AND GEOTECHNICAL EVALUATION NEW ACADEMIC BUILDING LAS POSITAS COLLEGE LIVERMORE, CALIFORNIA

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1 GEOLOGIC HAZARDS ASSESSMENT AND GEOTECHNICAL EVALUATION NEW ACADEMIC BUILDING LAS POSITAS COLLEGE LIVERMORE, CALIFORNIA PREPARED FOR: Chabot-Las Positas Community College District 5020 Franklin Drive Pleasanton, California PREPARED BY: Ninyo & Moore Geotechnical and Environmental Sciences Consultants 1956 Webster Street, Suite 400 Oakland, California November 21, 2014 Project No

2 November 21, 2014 Project No Mr. Bruce Rich Chabot-Las Positas Community College District 5020 Franklin Drive Pleasanton, California Subject: Geologic Hazards Assessment and Geotechnical Evaluation New Academic Building Las Positas College Livermore, California Dear Mr. Rich: Thank you for the opportunity to perform this geologic hazards assessment and geotechnical evaluation for the New Academic Building to be located at Las Positas College in Livermore, California. This report presents our geologic hazards assessment and our geotechnical findings, conclusions, and recommendations regarding the proposed project. As an integral part of our role as the geotechnical engineer-of-record, we request the opportunity to review the construction plans before they go to bid and to provide follow-up construction observation and testing services. We appreciate the opportunity to be of service on this project. Sincerely, NINYO & MOORE Francis O. Moreland Senior Geologist Kapil Gupta, P.E., G.E. Senior Engineer Peter C. Connolly, P.E., G.E. Principal Engineer RH/FOM/KG/PCC/vmp Distribution: (1) Addressee

3 TABLE OF CONTENTS Page 1. INTRODUCTION SCOPE OF SERVICES SITE DESCRIPTION PROJECT DESCRIPTION FIELD EXPLORATION AND LABORATORY TESTING GEOLOGY AND SUBSURFACE CONDITIONS Regional Geologic Setting Site Geology Subsurface Conditions Alluvial Overbank Deposit Alluvium Groundwater GEOLOGIC HAZARDS AND GEOTECHNICAL ISSUES Seismic Hazards Historical Seismicity Faulting and Ground Surface Rupture Seismic Ground Motion Liquefaction and Strain Softening Dynamic Settlement Seismic Slope Stability Tsunamis and Seiches Landsliding and Slope Stability Flood Hazards and Dam Inundation Expansive Soils Unsuitable Materials Static Settlement Corrosive/Deleterious Soils Excavation Characteristics CONCLUSIONS RECOMMENDATIONS Earthwork Site Preparation Observation and Removals Excavation Stabilization and Temporary Slopes Construction Dewatering Utility Trenches Material Requirements Lime Treatment of Expansive Soils...20 iii

4 Subgrade Preparation Fill Placement and Compaction Rainy Weather Considerations Foundations Slab-On-Grade Foundations Lateral Resistance of Shallow Foundations Seismic Design Considerations Exterior Flatwork Concrete Moisture Vapor Retarder Drainage and Site Maintenance Review of Construction Plans Pre-Construction Conference Construction Observation and Testing LIMITATIONS REFERENCES...34 Tables Table 1 Historical Earthquakes...7 Table 2 Criteria for Deleterious Soil on Concrete...14 Table 3 Recommended OSHA Material Classifications and Allowable Slopes...18 Table 4 Recommended Material Requirements...20 Table 5 Subgrade Preparation Recommendations...22 Table 6 Recommended Compaction Requirements...23 Table 7 Recommended Bearing Design Parameters for Footings...25 Table 8 Recommended Lateral Design Parameters for Shallow Foundations...26 Table 9 California Building Code Seismic Design Criteria...27 Figures Figure 1 Site Location Figure 2 Boring Locations Figure 3 Regional Geology Figure 4 Geologic Cross Section A-A Figure 5 Geologic Cross Section B-B Figure 6 Fault Locations Figure 7 Seismic Hazard Zones Appendices Appendix A Boring Logs Appendix B Laboratory Testing iv

5 1. INTRODUCTION In accordance with your request, we have performed a geologic hazards assessment and geotechnical evaluation for the New Academic Building to be located at Las Positas College in Livermore, California (Figure 1). The purpose of our study was to evaluate the potential geologic hazards and geotechnical conditions at the subject site, and provide recommendations for the design and construction of this project. Our evaluation was conducted in conformance with the guidelines contained in California Geological Survey Note 48, Checklist for the Review of Engineering Geology and Seismology Reports for California Public Schools, Hospitals, and Essential Services Buildings, used by the California Geological Survey (CGS) in their evaluation of geologic hazard reports for conformance with the requirements of the California Division of the State Architect (DSA) Interpretation of Regulations Document IR A-4, revised December 19, The latest version of CGS s Note 48 is dated October, Our evaluation is also in conformance with Chapter 18A of Title 24, Part 2, Volume 2 of the 2013 California Building Code (CBC). Ninyo & Moore previously conducted geotechnical and geologic hazard studies for the Student Services and Administration Building located to the east of the current site. Results from those studies were presented in a report titled, Geologic Hazards Assessment and Geotechnical Evaluation, Student and Administrative Services Building, Las Positas College, Livermore, California, dated June 17, 2008 (Ninyo & Moore, 2008) and a report titled Geologic Hazards Assessment and Geotechnical Evaluation, Student and Administrative Services Building, Las Positas College, Livermore, California, dated November 3, 2009 (Ninyo & Moore, 2009b) 2. SCOPE OF SERVICES Ninyo & Moore s scope of services for this evaluation included the following tasks: Review of background data listed in the References section of this report. The data reviewed included geotechnical reports by Ninyo & Moore, topographic maps, geologic data and maps, fault and seismic hazard maps, landslide hazard maps, flood hazard maps, and a conceptual site plan (Lionakis, 2014) for the project. 1

6 Performance of a site reconnaissance to observe the surficial geotechnical conditions and to mark the proposed boring locations for utility marking services. Coordination with Underground Service Alert (USA) and Las Positas College facilities personnel to locate the underground utilities in the vicinity of the proposed borings. Performance of a private utility location survey to further evaluate subsurface utilities. Procurement of a geotechnical exploration boring permit from Zone 7 Water Agency. Performance of a subsurface evaluation consisting of drilling, logging, and sampling of four small-diameters, hollow-stem auger borings. A representative of Ninyo & Moore logged the subsurface conditions exposed in the borings, and collected bulk and relatively undisturbed samples for laboratory testing. The exploratory borings were backfilled in accordance with the requirements of the Zone 7 Water Agency, and ground surface was patched with appropriated materials where needed. Disposal of soil cuttings from the exploratory borings at a designated on-site location. Laboratory testing on soil samples recovered during the subsurface study to evaluate in-situ moisture and dry density, Atterberg limits, expansion index, and soil corrosivity. Engineering analysis of the gathered data to evaluate geotechnical considerations for the proposed improvements, including seismic parameters, liquefaction potential, foundation design criteria, and earthwork guidelines. Preparation of this geotechnical report presenting our findings and conclusions regarding the geotechnical conditions encountered at the project site, and our recommendations for the design and construction of the project. 3. SITE DESCRIPTION The project site is located east of the San Francisco Bay in the Livermore Valley, which transects the northwest-southeast trending Diablo Range in an east-west direction. The Las Positas College campus is an irregularly-shaped parcel that encompasses approximately 147 acres of gently sloping land. The campus is located approximately 3,500 feet north of Highway 580 and east of Collier Canyon Road on a gently inclined southwest-facing slope (Figure 1). A perimeter road circles the campus, linking the parking lots located around the campus buildings. The site is bordered to the west, north, and east by campus buildings and to the south by a campus parking lot. 2

7 As shown on Figure 1, the New Academic Building site is located at approximately degrees north latitude and degrees west longitude. The project site, as shown on Figure 2, is currently occupied by three campus buildings (Buildings 100, 200, and 300) and portions of existing landscape. The site is approximately level, with elevations ranging from approxapproximately 471 to 472 feet Mean Sea Level (MSL) (Google Earth, 2013). 4. PROJECT DESCRIPTION Based on the conceptual site plan and associated information prepared by Lionakis we understand that the New Academic Building will be a two story structure with a footprint area of approximately 17,500 square feet. Building loads are expected to be typical of this type of construction. We anticipate that existing buildings 100, 200, and 300 will be demolished prior to the construction of the New Academic Building. 5. FIELD EXPLORATION AND LABORATORY TESTING Our field study included a geologic reconnaissance and subsurface exploration conducted on September 26 and October 17, The subsurface exploration consisted of drilling, logging, and sampling of four (4) small-diameter borings. The boring locations, as shown on Figure 2, were selected based on the results of our field reconnaissance and the currently proposed building. Prior to commencing the subsurface exploration, we contacted Underground Service Alert (USA) to notify utility owners to locate and mark existing utilities on site. We consulted with facilities personnel and a private utility locator to further evaluate the location of existing utilities. A drilling permit was obtained from the Zone 7 Water Agency. The borings were drilled to depths of approximately 25 to 50 feet below the existing grade with a truck-mounted drill rig equipped with hollow-stem auger. A representative of Ninyo & Moore logged the subsurface conditions exposed in the borings and collected representative soil samples from the borings. The samples were then transported to our geotechnical laboratory for testing. The borings were backfilled after drilling in conformance with the Zone 7 permit. De- 3

8 scriptions of the subsurface materials encountered are presented in the following sections. Detailed logs of the borings are presented in Appendix A. Laboratory testing of soil samples was performed to evaluate in-situ moisture content, dry density, Atterberg limits, expansion potential, and soil corrosivity. The results of the in-situ moisture content and dry density tests are shown at the corresponding sample depths on the boring logs in Appendix A. The results of the other laboratory tests performed are presented in Appendix B. 6. GEOLOGY AND SUBSURFACE CONDITIONS Our findings regarding regional and site geology and groundwater conditions at the subject site are provided in the following sections Regional Geologic Setting The site is located east of San Francisco Bay in the Coast Ranges geomorphic province of California. The Coast Ranges are comprised of several mountain ranges and structural valleys formed by tectonic processes commonly found around the Circum-Pacific belt. Basement rocks have been sheared, faulted, metamorphosed, and uplifted, and are separated by thick blankets of Cretaceous and Cenozoic sediments that fill structural valleys and line continental margins. The San Francisco Bay area has several ranges that trend northwest, parallel to major strike-slip faults such as the San Andreas, Hayward, and Calaveras. Major tectonic activity associated with these and other faults within this regional tectonic framework consists primarily of right-lateral, strike-slip movement Site Geology The project site is mapped as being underlain by Quaternary-aged alluvial/surficial deposits by Graymer et al. (1996), Majmunder (1991), Dibblee (2006), Herd (1977), and Crane (1995). Dibblee (2006) describes the unit as alluvial gravel, sand, and clay of the valley areas, while Graymer (1996) describes the unit as unconsolidated sand, silt, gravel, and clay deposits. The findings of our subsurface evaluation (described below), indicate that the sub- 4

9 ject site is underlain by Quaternary alluvium. A Regional Geologic Map prepared by Graymer et al (1996) is provided as Figure Subsurface Conditions Materials encountered during our subsurface evaluation included native soils consisting of an aluvial overbank deposit underlain by older alluvium. Generalized descriptions of the units encountered are provided in subsequent sections. More detailed descriptions are presented on the boring logs in Appendix A. Cross sections depicting our interpretation of the site geology are provided on Figures 4 and Alluvial Overbank Deposit An alluvial overbank deposit was encountered in the borings to a depth of about 5 to 8½ feet. As encountered, this unit is generally highly expansive, consisting of dark brown, moist, very stiff, fat clay with trace sand and scattered organics Alluvium Alluvium was encountered in the borings from below the alluvial overbank deposit to the depths explored. As encountered, the alluvium generally consisted of light olive brown, moist, stiff to hard, clay and silt with trace to some sand. Caliche in the form of nodules and thin layers was encountered at various depths within the alluvium Groundwater Groundwater was not encountered in our exploratory borings. However, fluctuations in the groundwater level may occur due to variations in ground surface topography, subsurface geologic conditions and structure, rainfall, irrigation, and other factors. The map of historic high groundwater levels presented within the Seismic Hazard Zone Report for the Livermore Quadrangle (CGS, 2008a) indicates that the project site is within an area where information regarding the depth to historic high groundwater is not available. 5

10 7. GEOLOGIC HAZARDS AND GEOTECHNICAL ISSUES This study considered a number of potential issues relevant to the proposed construction, including seismic hazards, expansive soils, unsuitable materials, landsliding, slope stability, flood hazards, settlement of compressible soil layers from static loading, soil corrosivity, and excavation characteristics. These issues are discussed in the following subsections Seismic Hazards The seismic hazards considered in this study include the potential for ground rupture and ground shaking due to seismic activity, seismically induced liquefaction, dynamic settlement, tsunamis, and seiches. These potential hazards are discussed in the following subsections Historical Seismicity The site is located in a seismically active region, as is the majority of northern California. Table 1 summarizes the significant historic earthquakes that have occurred within a radius of approximately 50 kilometers of the site with a magnitude of 5.5 or more since

11 Table 1 Historical Earthquakes Date Magnitude 1 Epicentral Distance 1 (M) km (miles) February 15, (30.9) November 26, (14.5) July 4, (8.6) March 5, (11.2) May 21, (9.3) July 15, (16.5) October 21, (16.3) April 2, (30.2) May 19, (26.9) July 31, (22.6) January 2, (28.3) August 3, (28.3) January 24, (8.5) April 24, (28.5) March 31, (17.2) Note: 1 CGS: In addition to these significant earthquakes, an earthquake centered along the Greenville fault, about 14 kilometers northeast of the project site, took place at 11:00 am, Pacific Standard Time, on January 24, 1980 (United States Geological Survey [USGS], 2014). Reported magnitudes for this earthquake include: 5.9 surface wave magnitude (USGS, 2014); 5.9 Richter magnitude (Scheimer et al., 1982); 5.8 undefined magnitude (USGS, 2012); and 5.5 Richter magnitude (California Division of Mines and Geology [CDMG], 1980). Associated surface rupture extended approximately 6 kilometers along the Greenville fault, beginning near the overpass at Interstate 580 and Greenville Road (USGS, 2012). The earthquake caused more than $11.5 million in property damage, with $10 million of this at the Lawrence Livermore Laboratory. A majority of this damage was non-structural, and included broken windows, broken gas and water lines, and mobile homes displaced from their foundations. Damage at Lawrence Livermore Laboratory included broken PVC pipes, paneling, glassware, and overturned bookshelves (USGS, 2012; CDMG, 1980). 7

12 A small foreshock preceded the earthquake by 1½ minutes, and the earthquake was followed by a swarm of aftershocks over the next several days. There is conflicting information regarding the largest of these aftershocks, which occurred on January 26, 1980 (USGS, 2014; USGS, 2012; Scheimer et al. 1982; CDMG, 1980). Reported magnitudes for this event include: 5.8 Richter magnitude (USGS, 2014); 5.3 Richter magnimagnitude (Scheimer et al., 1982); and Richter magnitude (CDMG, 1980). The referenced documents contained no discussion about damage at the Las Positas College campus resulting from the series of tremors. Our air photo review during the previous studies for the Las Positas College campus indicated that the campus was in the early stages of development at the time of the January 24, 1980, Livermore Earthquake, and there is no evidence to suggest that any structures were damaged during this event Faulting and Ground Surface Rupture The numerous faults in northern California include active, potentially active, and inactive faults. As defined by the CGS, active faults are faults that have ruptured within Holocene time, or within approximately the last 11,000 years. Potentially active faults are those that show evidence of movement during Quaternary time (approximately the last 1.6 million years) but for which evidence of Holocene movement has not been established. Inactive faults do not show evidence of movement within Quaternary time. The site is not located within an Alquist-Priolo Fault Rupture Hazard Zone established by the state geologist (CDMG, 1982) to delineate regions of potential ground surface rupture adjacent to active faults. The closest known active fault is the Mount Diablo Thrust fault located approximately 1.8 miles (2.9 kilometers) northwest of the project site. Major known active faults in the region consist generally of en-echelon, northweststriking, right-lateral, strike-slip faults. These include the Calaveras, Hayward, and San Andreas faults, located west of the site, and the Greenville fault, located east of the site. 8

13 The approximate locations of major faults in the region and their geographic relationship to the project vicinity are shown on Figure 6. The closest fault to the project site indicated on published maps (Dibblee, 2006; Graymer, 1996; Jennings, 2010; Crane, 1995; Majmunder, 1991) is located along the base of the hills about 400 feet north of the project site (Figure 3). Jennings (2010) refers to this fault, perpendicular and north of the Livermore fault, as a Quaternary fault with evidence of displacement in the last 1.6 million years. Graymer et al. (1996), Crane (1995), and Majmunder (1991) interpret the fault as a thrust feature, with the hanging wall to the north of the fault trace, while Dibblee (2006) indicates that the north side of the fault is moving up relative to the south side. Detailed mapping by Dibblee (2006) and Majmunder (1991) indicates that the fault is exposed in the Pliocene to Pleistocene Livermore Gravels, but is generally concealed by Holocene alluvium. Based upon the information presented above, the fault located approximately 400 feet north of the project site should be considered potentially active. The trace of this fault, as interpreted by the referenced authors, does not cross the proposed building site, and it is the opinion of Ninyo & Moore that sympathetic movement along the fault resulting from a seismic event on nearby active faults, such as the Greenville fault or Mount Diablo thrust, will not impact the proposed improvements. Additionally, Ninyo & Moore previously performed a subsurface fault trenching study to evaluate if northwest-trending lineaments observed in aerial photographs as projecting onto the Las Positas Community College Campus were related to faulting. No evidence of faulting was found within the approximately 660-foot-long trench excavation performed across these lineaments (Ninyo & Moore, 2007a). Based on our review of the referenced geologic maps, and the results of our previous fault trenching study, it is our opinion that the New Academic Building site is not underlain by known active or potentially active faults (i.e., faults that exhibit evidence of ground displacement in the last 11,000 years and 1,600,000 years, respectively). There- 9

14 fore, the potential for ground surface rupture due to faulting at the site is considered low. However, lurching or cracking of the ground surface as a result of nearby seismic events is possible Seismic Ground Motion The 2013 California Building Code (CBC) specifies that the Risk-Targeted, Maximum Considered Earthquake (MCE R ) ground motion response accelerations be used to evaluate seismic loads for design of buildings and other structures. The MCE R ground motion response accelerations are based on the spectral response accelerations for 5 percent damping in the direction of maximum horizontal response and incorporate a target risk for structural collapse equivalent to 1 percent in 50 years with deterministic limits for near-source effects. The horizontal peak ground acceleration (PGA) that corresponds to the MCE R for the site was calculated as 0.79g using the United States Geological Survey (USGS, 2013) seismic design tool (web-based). The 2013 CBC specifies that the potential for liquefaction and soil strength loss be evaluated, where applicable, for the Maximum Considered Earthquake Geometric Mean (MCE G ) peak ground acceleration with adjustment for site class effects in accordance with the American Society of Civil Engineers (ASCE) 7-10 Standard. The MCE G peak ground acceleration is based on the geometric mean peak ground acceleration with a 2 percent probability of exceedance in 50 years. The MCE G peak ground acceleration with adjustment for site class effects (PGA M ) was calculated as 0.74g using the USGS (USGS, 2013) seismic design tool that yielded a mapped MCE G peak ground acceleration of 0.74g for the site and a site coefficient (F PGA ) of 1.00 for Site Class D Liquefaction and Strain Softening The strong vibratory motions generated by earthquakes can trigger a rapid loss of shear strength in saturated, loose, granular soils of low plasticity (liquefaction) or in wet, sensitive, cohesive soils (strain softening). Liquefaction and strain softening can result in a loss of foundation bearing capacity or lateral spreading of sloping or unconfined 10

15 ground. Liquefaction can also generate sand boils leading to subsidence at the ground surface. The site is not located within a liquefaction hazard zone on the Seismic Hazard Zones Map (Figure 7) prepared by the CGS (CGS, 2008b). Moreover, we did not encounter saturated, loose, cohesionless, granular soils during our subsurface exploration. The cohesion and fines content of the granular material encountered in our subsurface exploration generally did not conform with the characteristics of liquefiable soils published by Bray and Sancio (2006). The cohesive soils encountered were not particularly wet or sensitive. As such, we do not regard liquefaction, strain softening, or related hazards as design considerations Dynamic Settlement The strong vibratory motion associated with earthquakes can also dynamically compact loose granular soil leading to surficial settlements. Dynamic settlement is not limited to the near-surface environment and may occur in both dry and saturated sand and silt. Cohesive soils are not typically susceptible to dynamic settlement. Based on the generally stiff to hard consistency and cohesive nature of the on-site materials, we do not regard dynamic settlement on-site as a design consideration Seismic Slope Stability The site is not located within a hazard zone for earthquake-induced landslides on the Seismic Hazard Zones Map (Figure 7) prepared by the CGS (CGS, 2008b). As such, we do not regard seismic slope stability as a design consideration Tsunamis and Seiches Tsunamis are long wavelength seismic sea waves (long compared to ocean depth) generated by the sudden movements of the ocean floor during submarine earthquakes, landslides, or volcanic activity. The project location is not within a tsunami evacuation 11

16 area as shown on the Tsunami Evacuation Planning Map for Alameda County presented by the Association of Bay Area Governments (ABAG, 2009). Seiches are waves generated in a large enclosed body of water. Based on the inland location of the site and considering that there are no large enclosed bodies of water nearby, the potential for damage due to tsunamis or seiches is not a design consideration Landsliding and Slope Stability The site of the proposed construction is relatively flat. We did not observe indications of landslides on slopes within the project limits during our site reconnaissance. As such, we do not regard landsliding or slope stability as a design consideration Flood Hazards and Dam Inundation Our review of Federal Emergency Management Agency (FEMA) Flood Insurance Rate Maps (FEMA, 2009) found that the site is in an area considered to be outside the 0.2% annual chance flood plain. Based on a review of the Dam Failure Inundation Maps prepared by the Association of Bay Area Governments (ABAG, 2009), the site is not located within an inundation area following a conjectured catastrophic dam failure Expansive Soils Some clay minerals undergo volume changes upon wetting or drying. Unsaturated soils containing those minerals will shrink/swell with the removal/addition of water. The heaving pressures associated with this expansion can damage structures and flatwork. Laboratory testing was performed on select samples of the near-surface soil to evaluate the expansion index. The tests were performed in general accordance with the American Society of Testing and Materials (ASTM) Standard D 4829 (Expansion Index). The results of our laboratory testing indicate that the expansion index of the near-surface soil ranges from 97 and 111. This result is indicative of a high expansion characteristic. Geotechnical evaluations for other projects on campus (Ninyo & Moore 2007b, 2008, and 2009) have also found that the near-surface soils generally have a high expansion characteristic. We anticipate that the dif- 12

17 ferential movement related to the shrink/swell behavior of this material, if located near the ground surface after grading, will be unacceptable for overlying slabs, pavement, flatwork, and lightly-loaded shallow footings. We provide recommendations in Section to remove this material during site grading and replace it with imported fill or on-site select borborrow with low expansion characteristics to reduce the potential for differential movement due to expansive soils. The removed material may be stockpiled and re-used as fill below the zone of influence for pavements, slabs, and footings. Alternative recommendations are provided in Section to treat the expansive soil with lime to reduce the expansion characteristic Unsuitable Materials Soils containing roots or other organic matter are not suitable as fill or subgrade material below structures, pavements, or engineered fill. Surficial soils containing roots or other organic matter should be removed as part of the clearing and grubbing operations Static Settlement We understand that proposed improvements will be relatively light and that significant changes to the site grade are not proposed. We anticipate, therefore, that settlement due to sustained loading by the proposed improvements will be tolerable provided that those improvements are supported on shallow foundations designed in accordance with the recommendations in this report Corrosive/Deleterious Soils An evaluation of the corrosivity of the on-site materials was conducted to assess the impact to concrete and metals. The corrosion impact was evaluated using the results of limited laboratory testing on a sample obtained during our subsurface study. Laboratory testing to evaluate electrical resistivity, chloride content, and soluble sulfate content was performed on the sample. The results of the corrosivity tests are presented in Appendix B. 13

18 California Department of Transportation (Caltrans) defines a corrosive environment as an area within 1,000 feet of brackish water or where the soil contains more than 500 parts per million (ppm) of chlorides, sulfates of 0.2 (2,000 ppm) percent or more, or ph of 5.5 or less (Caltrans, 2012). The criteria used to evaluate the deleterious nature of soil on concrete are listed in Table 2. Based on these criteria, the soil on site does not meet the definition of a corrosive environment and the sulfate exposure to concrete is negligible. Ferrous metal will still undergo corrosion on site, but special mitigation measures are not needed. Table 2 Criteria for Deleterious Soil on Concrete Sulfate Content Percent by Weight Sulfate Exposure 0.0 to 0.1 Negligible 0.1 to 0.2 Moderate 0.2 to 2.0 Severe > 2.0 Very Severe Reference: American Concrete Institute (ACI) Committee 318 Table (ACI, 2012) 7.8. Excavation Characteristics We anticipate that the proposed project will involve excavations of up to a few feet for footings, utility trenches, or removal of unsuitable or expansive materials. The surficial geologic units encountered during our subsurface evaluation consisted primarily of stiff to hard clay and silt. We anticipate that heavy earthmoving equipment in good working condition should be able to make the proposed excavations. Near-vertical cuts in these deposits up to 5 feet in depth should remain stable for a limited period of time. Sloughing of the sidewall may occur, however, particularly if the sidewall is disturbed during construction operations or exposed to water. Recommendations for excavation stabilization are presented in Sections

19 8. CONCLUSIONS Based on the results of our geotechnical evaluation, it is our opinion that the proposed improvements are feasible from a geotechnical standpoint provided the recommendations presented in this report are incorporated into the design and construction of the subject project. In addition, the following issues might impact the construction and performance of the proposed improvements: The site could experience a relatively large degree of ground shaking during a significant earthquake on a nearby fault. Some near-surface site soils have a high expansion characteristic. To reduce the potential for differential movement of the proposed improvements due to shrink/swell behavior, we provide recommendations to remove or exclude these materials from the zone of influence below the proposed improvements. Recommendations for removal and replacement below structures and flatwork and subsurface drainage improvements for pavements are presented in the following sections of this report. Alternative recommendations for lime treatment to mitigate the expansion potential of on-site soils are also provided. Some near-surface soils at the subject site contain organic matter. Recommendations for removal of this material are presented in Section Based on the results of our limited soil corrosivity tests during this study and Caltrans corrosion guidelines (2012), the site does not meet the definition of a corrosive environment. 9. RECOMMENDATIONS The following guidelines should be used in the preparation of the construction plans Earthwork The earthwork should be conducted in accordance with the relevant grading ordinances having jurisdiction over the project area and the following recommendations. The geotechnical engineer should observe earthwork operations. Evaluations performed by the geotechnical engineer during the course of operations may result in new recommendations, which could supersede the recommendations in this section. 15

20 Site Preparation Prior to performing earthwork operations, the site should be cleared of vegetation, surface soils containing roots or other organic matter, surface obstructions (e.g., pavements, aggregate base, etc.), rubble and debris, abandoned utilities, and other deleterious materials. Existing utilities within the project limits, if any, should be rerouted or protected from damage by construction activities. Trees or other obstructions that extend below finish grade, if any, should be removed and the resulting holes filled with compacted soils. Materials generated from the clearing operations should be removed from the project site and disposed of at a legal dumpsite. Soils containing roots or other organic matter may be stockpiled for later use as landscaping fill, as authorized by the District s representative Observation and Removals Prior to placement of fill or the erection of forms, the District should request an evaluation of the exposed subgrade by the geotechnical consultant. Materials that are considered unsuitable shall be excavated under the observation of the geotechnical consultant in accordance with the recommendations in this section, or the field recommendations of the geotechnical engineer. Unsuitable materials include, but may not be limited to dry, loose, soft, wet, expansive, organic, or compressible natural soils; and undocumented or otherwise deleterious fill materials. Unsuitable materials should be removed from below footings, slabs, and areas to receive fill to the depth of suitable material as evaluated by the geotechnical engineer in the field. Some on-site soils have a high expansion characteristic, particularly the dark brown clay generally found within the upper portion of the native soil profile. We recommend that highly expansive soils be removed or excluded from within 3 feet of the finish subgrade below structures and 2 feet below the exterior flatwork to reduce the potential for differential movement and distress to the proposed improvements due to shrink/swell 16

21 behavior. The expansive soil may be re-used as general fill below a depth of 3 feet from the finish grade, provided that the material complies with our recommendations for general fill in Section Alternatively, the expansive soil may be treated with lime to reduce its expansive characteristics in accordance with our recommendations in Section The zone of exclusion/removal or lime treatment should be detailed on the construction plans to reduce the potential that these recommendations are overlooked during construction bidding Excavation Stabilization and Temporary Slopes Excavations, including footing and trench excavations, shall be stabilized in accordance with the Excavation Rules and Regulations (29 Code of Federal Regulations, Part 1926) stipulated by the Occupational Safety and Health Administration (OSHA). Stabilization shall consist of shoring sidewalls or laying slopes back. Table 3 lists the OSHA material type classifications and corresponding allowable temporary slope layback inclinations for soil deposits that may be encountered on site. Alternatively, a shoring system conforming to the OSHA Excavation Rules and Regulations (29 CFR Part 1926) may be used to stabilize excavation sidewalls during construction. Shoring system criteria for excavations up to 20 feet in depth are listed in the OSHA Excavation Rules and Regulations (29 CFR Part 1926). The lateral earth pressures listed in Table 3 may be used to design or select the shoring system. The recommendations listed in this table are based upon the limited subsurface data provided by our exploratory borings and excavations and reflect the influence of the environmental conditions that existed at the time of our exploration. Excavation stability, material classifications, allowable slopes, and shoring pressures should be re-evaluated and revised, as needed, during construction. Excavations, shoring systems and the surrounding areas should be evaluated daily by a competent person for indications of possible instability or collapse. 17

22 Table 3 Recommended OSHA Material Classifications and Allowable Slopes Formation OSHA Classification Allowable Temporary Slope 1,2,3 Lateral Earth Pressure on Shoring 4, (psf) Alluvial Overbank Deposit Type B 1h:1v (45 ) 45 D Alluvium Type B 1h:1v (45 ) 45 D + 72 Allowable slope for temporary excavations less than 20 feet deep. Excavation sidewalls in cohesive soils may be benched to meet the allowable slope criteria (measured from the bottom edge of the excavation). The allowable bench height is 4 feet. The bench at the bottom of the excavation may protrude above the allowable slope criteria. In layered soils, no layer shall be sloped steeper than the layer below. Temporary excavations less than 4 feet deep may be made with vertical side slopes and remain unshored if judged to be stable by a competent person (29 CFR Part ). D is depth of excavation for excavations up to 20 feet deep. Includes a surface surcharge equivalent to two feet of soil. The shoring system should be designed or selected by a suitably qualified individual or specialty subcontractor. The shoring parameters presented in this report are preliminary design criteria, and the designer should evaluate the adequacy of these parameters and make appropriate modifications for their design. We recommend that the contractor take appropriate measures to protect workers. OSHA requirements pertaining to worker safety should be observed. We understand that the proposed excavations will not be in close proximity to existing structures. Excavations made in close proximity to existing structures may undermine the foundation of those structures and/or cause soil movement related distress to the existing structures. Stabilization techniques for excavations in close proximity to existing structures will need to account for the additional loads imposed on the shoring system and appropriate setback distances for temporary slopes. The geotechnical engineer should be consulted for additional recommendations if the proposed excavations cross below a plane extending down and away from the foundation bearing surfaces of the adjacent structure at an angle of 2:1 (horizontal to vertical). 18

23 Construction Dewatering Groundwater was not encountered in our exploratory borings. However, significant fluctuations in the groundwater level may occur as a result of variations in seasonal precipitation and other factors. Water intrusion into the excavations may occur as a result of groundwater intrusion or surface runoff. The contractor should be prepared to take appropriate dewatering measures in the event that water intrudes into the excavations. Considerations for construction dewatering should include anticipated drawdown, volume of pumping, potential for settlement, and groundwater discharge. Disposal of groundwater should be performed in accordance with the guidelines of the Regional Water Quality Control Board Utility Trenches Trenches constructed for the installation of underground utilities should be stabilized in accordance with our recommendations presented in Section Utility trenches should be backfilled with materials that conform to our recommendations in Section Bedding materials should conform to the specifications of the pipe or conduit manufacturer. Trench backfill should be compacted in accordance with Section of this report. Trench backfill should be compacted by mechanical means. Densification of trench backfill by flooding or jetting is not recommended. To reduce potential for moisture intrusion into building envelopes, we recommend plugging utility trenches at locations where the trench excavations cross under building perimeters. The trench plug should be constructed of a compacted, fine-grained, cohesive soil that fills the cross-sectional area of the trench for a distance equivalent to the depth of the excavation. Alternatively, the plug may be constructed of lean concrete, controlled low strength material (CLSM), or flowable fill Material Requirements Materials used during earthwork, grading, and paving operations should comply with the requirements listed in Table 4. Materials should be evaluated by the geotechnical 19

24 consultant for suitability prior to use. The contractor should notify the geotechnical consultant 72 hours prior to import of materials or use of on-site materials to permit time for sampling, testing, and evaluation of the proposed materials. Table 4 Recommended Material Requirements Material and Use Source Requirements 1,2,3 Select Structural Fill 3 feet below the finished grade 4 2 feet below walkway slabs General Fill for uses not otherwise specified Capillary Break Gravel part of vapor retarding system below select slabs-on-grade Vapor Retarding Membrane Pipe/Conduit Bedding Material below conduit invert to 12 inches above conduit Trench Backfill above bedding material Import or On-site borrow Expansion Index of 50 or less 5 On-site borrow (treated with lime) Plasticity Index of 10 or less On-site borrow No additional requirements 1 Import Import Import Import or on-site borrow Open-graded, clean, compactable crushed rock or angular gravel; nominal size 3/4 or less 15 mil, Class A plastic membrane as per ASTM E to 100 percent (by mass) should pass No. 4 sieve, and 5 percent or less should pass No. 200 sieve Free from rock/lumps in excess of 4 diameter or 2 diameter in top 12 ; As per select fill in top 3 feet 1 In general, fill should be free of rocks or lumps in excess of 6-inches diameter, trash, debris, roots, vegetation or other deleterious material. 2 In general, import fill should be tested or documented to be non-corrosive 3 and free from hazardous materials in concentrations above levels of concern. 3 Non-corrosive as defined by the Corrosion Guidelines version 2.0 (Caltrans, 2012). 4 Placed below a plane extending down and away from the outer edges of footings/slabs at 2:1 (horizontal to vertical) angle Lime Treatment of Expansive Soils In lieu of importing select material or locating on-site borrow with low expansion characteristics, on-site material may be mixed with lime to create a 3-foot-thick zone of low expansion potential material below the building foundation elements and 2-foot thick zone below exterior flatwork. On-site materials containing roots or other organic matter are not suitable for lime treatment and should be stripped from the area at which the 20

25 lime treatment is to be performed. A specialty contractor should be consulted to select the lime content and mixing procedure to reduce the plasticity index of the treated soil to 10 or less. The lime or selected stabilizing agent may be spread in dry form or as slurry. Dry lime should be spread and mixed in a fashion that reduces potential for dusting. Casting or tailgating of dry lime is not recommended. The spreading and mixing procedure should produce a consistent distribution of stabilizing agent in the treated soil. Mixing and pulverizing should continue until the treated soil does not contain untreated soil clods larger than 1 inch and the quantity of untreated soil clods retained on the No. 4 sieve is less than 40 percent of the dry soil mass. Periodic testing should be performed to evaluate the plasticity index of the treated soil Subgrade Preparation Subgrade below footings, slabs, pavement, walkways or fill, should be prepared as per the recommendations in Table 5. Recommendations for subgrade preparation for footings bearing on expansive subgrade are provided for retaining walls and deepened structural footings. 21

26 Table 5 Subgrade Preparation Recommendations Subgrade Location Utility Trenches Below Slabs, Walkways, Flatwork Below Footings Below Fill Preparation Recommendations o Do not scarify. Compact as per Section if disturbed. Remove or compact loose/soft material. o Remove unsuitable materials including expansive soils as per Sections and o Remove and replace expansive soil as per Section or lime treat as per Section o Keep in moist but not saturated condition by sprinkling water. o Remove unsuitable materials as per Section o Remove or moisture condition and compact loose or soft subgrade material as per Section o Keep in moist condition by sprinkling water. o Remove unsuitable materials as per Sections and o Scarify top 8 then moisture condition and compact as per Section o Keep in moist but not saturated condition by sprinkling water. Prepared subgrade should be maintained in a moist (but not saturated) condition by the periodic sprinkling of water prior to placement of additional overlying fill or construction of pavements, footings and slabs. Subgrade that has been permitted to dry out and loosen or develop desiccation cracking, should be scarified, moisture conditioned, and recompacted as per the requirements above Fill Placement and Compaction Fill and backfill should be compacted in horizontal lifts in conformance with the recommendations presented in Table 6. The allowable uncompacted thickness of each lift of fill depends on the type of compaction equipment utilized, but generally should not exceed 8 inches in loose thickness. Heavy compaction equipment should not be used in the zone of influence behind retaining walls. The zone of influence is the region above a plane extending up and away from the heel of the wall at a slope of about 2:1 (horizontal to vertical). 22

27 Table 6 Recommended Compaction Requirements Fill Type Location Recommended Compacted Density 1 Recommended Compacted Moisture 2 Subgrade Conduit Bedding Trench Backfill Select Fill Below pavements and sidewalks 95 percent At or near optimum Below fill, structures 3, and walkways Material below conduit invert to 12 inches above conduit 3 feet below pavements & sidewalks 90 percent At or near optimum 90 percent At or near optimum 95 percent At or near optimum In locations not already specified 90 percent At or near optimum Below pavements and sidewalks 95 percent At or near optimum Below structures 3, and walkways 90 percent At or near optimum Aggregate Base Pavements, walkways & sidewalks 95 percent At or near optimum General Fill 5 feet below finished grade 95 percent At or near optimum Within 5 feet of finished grade 90 percent At or near optimum 1 Expressed as percent relative compaction or ratio of field density to reference density (typically on a dry density basis for soil and aggregate and on a wet density basis for asphalt concrete). The reference density of soil and aggregate should be evaluated by ASTM D The reference density of asphalt concrete should be evaluated by California Test Method Optimum moisture should be evaluated by ASTM D Placed below a plane extending down and away from the outer edges of footings/slabs at 1:1 angle. Compacted fill should be maintained in a moist (but not saturated) condition by the periodic sprinkling of water prior to placement of additional overlying fill or construction of footings and slabs. Fill that has been permitted to dry out and loosen or develop desiccation cracking, should be scarified, moisture conditioned, and recompacted as per the requirements above Rainy Weather Considerations We recommend that the construction be performed during the period between approximately April 15 and October 15 to avoid the rainy season. In the event that grading is performed through the rainy season, the plans for the project should be supplemented to include a stormwater management plan prepared in accordance with the requirements of 23

28 the relevant agency having jurisdiction. The plan should include details of measures to protect the subject property and adjoining off-site properties from damage by erosion, flooding or the deposition of mud, debris, or construction-related pollutants, which may originate from the site or result from the grading operation. The protective measures should be installed by the commencement of grading, or prior to the start of the rainy season. The protective measures should be maintained in good working order unless the drainage system is installed by that date and approval has been granted by the building official to remove the temporary devices. In addition, construction activities performed during rainy weather may impact the stability of excavation subgrade and exposed ground. Temporary swales should be constructed to divert surface runoff away from excavations and slopes. Steep temporary slopes should be covered with plastic sheeting during significant rains. The geotechnical engineer should be consulted for recommendations to stabilize the site as needed Foundations The following foundation design parameters and recommendations are provided based on our geotechnical analysis. The foundation design parameters are not intended to preclude differential movement of soils. Minor cracking (considered tolerable) of foundations may occur. Foundations should be designed in accordance with structural considerations and our geotechnical recommendations. In addition, the requirements of the governing jurisdictions, the practices of the Structural Engineers Association of California, and applicable building codes should be considered in the design of the structure Slab-On-Grade Foundations Structural loads for the New Academic building may be supported on a slab-on-grade foundation consisting of wall and column footings to carry structural loads with an interior slab-on-grade floor. The parameters listed in Table 7 should be used to design footings to resist vertical loads provided that unsuitable materials are removed from the 24

29 zone of influence below the footings as per Section and the subgrade is prepared in accordance with the recommendations in Section The geotechnical consultant should be provided an opportunity to observe the footing excavations to check that the actual bearing depth and exposed bearing materials are consistent with the assumed values. The thickness of unsuitable materials to be removed might exceed the assumed bearing depth. Footings should be deepened as needed to bear on suitable materials under the direction of the geotechnical engineer. Alternatively, the deepened footing trenches may be backfilled partially with CLSM to achieve the recommended bearing depth. Table 7 Recommended Bearing Design Parameters for Footings Supported Structure Assumed Bearing Material Footing Width Bearing Depth 1 D Allowable Bearing Capacity 2 q a column footing wall footing column footing wall footing Engineered Fill or Lime Treated Soil Stiff alluvium 24 inches or more 18 inches or more 24 inches or more 18 inches or more 24 inches 3,500 psf 36 inches 3,500 psf 1 Below the adjacent grade. Extend footing, as needed, to bear on native soil to mitigate differential fill/native bearing condition (see text). 2 Listed value includes a FOS of 3. Allowable bearing capacity may be increased by one-third when considering loads of short duration such as wind or seismic loads. Where footings are located adjacent to a trench or excavation that is nearly parallel to the footing alignment, the footing bearing surfaces should bear below an imaginary plane extending upward from the bottom edge of the adjacent trench/excavation at a 2:1 angle. Footings should be deepened or excavation depths reduced as needed. We recommend that footings and slabs be reinforced with deformed steel bars of sufficient rigidity to maintain the desired position within the footing or slab for a reasonable amount of support. We recommend that masonry briquettes or plastic chairs be used to aid in the correct placement of reinforcement. Footings and slabs should be designed by 25

30 the structural engineer based on the anticipated loading and usage. Refer to Section 9.5 for the recommended concrete cover over reinforcing steel. Slabs underlying enclosed spaces with humidity conditioned environments or slabs covered by moisture sensitive floor coverings should incorporate a moisture vapor retarding system into the design. See Section 9.7 for vapor retarding system recommendations Lateral Resistance of Shallow Foundations The parameters listed in may be used to evaluate the capacity of shallow foundations to resist lateral loads on the proposed project. Table 8 Recommended Lateral Design Parameters for Shallow Foundations Supported Structure New Academic Building Foundations Assumed Bearing Material Assumed Lateral Bearing Material Select Fill or Lime Treated Soil Friction Coefficient 2 Allowable Lateral Resistance 1 Base Adhesion 2 Lateral Fluid Pressure pcf Moisture Vapor Retarder pcf 1 Allowable lateral resistance can be taken as the sum of the lateral bearing and lateral sliding resistance. The lateral bearing resistance may be increased by one-third for load combinations including wind or seismic loads. 2 Lateral sliding resistance is the product of the friction coefficient and the base contact pressure or the product of the base adhesion and the base contact area, whichever is larger. Assumes that slabs or footings are poured rough against the subgrade and slabs have thickened edges. Lateral sliding resistance may not exceed one-half the dead load. 3 Lateral bearing resistance is the product of the lateral fluid pressure, the depth of embedment, and the lateral contact area, neglecting the top foot of embedment unless confinement is provided by an adjacent slab or pavement. The lateral fluid pressure does not include a factor of safety. The depth of embedment for lateral bearing resistance on sloping ground should be evaluated at a distance away from the footing equivalent to 300 percent of the footing embedment depth next to the footing. The designer should assume that the lateral bearing pressure does not increase below a depth of 10 feet Seismic Design Considerations Design of the proposed improvements should be performed in accordance with the requirements of the governing jurisdictions and applicable building codes. Table 10 presents the 26

31 seismic design parameters for the site in accordance with the CBC (2013) guidelines and adjusted MCE R spectral response acceleration parameters (USGS, 2013). Table 9 California Building Code Seismic Design Criteria Seismic Design Factor Value Soil Profile Type D Site Coefficient F a 1.00 Site Coefficient F v 1.50 Mapped MCE Spectral Acceleration at period of 0.2 seconds, S S Mapped MCE Spectral Acceleration at period of 1 second, S Site-Adjusted MCE Spectral Acceleration at period of 0.2 seconds, S MS Site-Adjusted MCE Spectral Acceleration at period of 1 second, S M Design Spectral Acceleration at period of 0.2 seconds, S DS Design Spectral Acceleration at period of 1 second, S D Seismic Design Category D 9.4. Exterior Flatwork Pedestrian sidewalks (adjacent to pavements) and walkways (removed from pavements carrying vehicular traffic) may be constructed of asphalt or Portland cement concrete. Asphalt concrete walkways should consist of 2 inches asphalt concrete over 4 inches of aggregate base. Portland cement concrete walkways should consist of 4 inches of concrete over 4 inches of aggregate base. These sections presume that the on-site expansive soils in the subgrade are mitigated by removal and replacement or lime treatment in accordance with our recommendations in Sections and 9.1.2, respectively, and the subgrade is prepared in accordance with our recommendations in Section Asphalt concrete, Portland cement concrete, and aggregate base materials should comply with our recommendations in the preceding sections. Aggregate base sections for walkways and sidewalks should be compacted in accordance with our recommendations in Section Portland cement concrete sidewalks and walkways should be appropriately jointed to reduce the random occurrence of cracks. Joints should be laid out in a regular square pattern. Con- 27

32 traction, construction, and isolation joints should be detailed and constructed in accordance with the guidelines of American Concrete Institute (ACI) Committee 302 (MCP, 2012). We recommend spacing contraction joints at 8 feet, or less Concrete Laboratory testing indicated that the concentration of sulfate and corresponding potential for sulfate attack on concrete is negligible for the soil tested. However, due to the variability in the on-site soils and the potential future use of reclaimed water at the site, we recommend that Type V or II/V cement be used for concrete structures in contact with soil. In addition, we recommend a water-to-cement ratio of 0.45, or less. A 3-inch thick, or thicker, concrete cover should be maintained over reinforcing steel where concrete is in contact with soil in accordance with Section 7.7 of ACI Committee 318 (ACI, 2012). In order to reduce the potential for shrinkage cracks in the concrete during curing, we recommend that the concrete for slabs, flatwork, or pavement should not contain large quantities of water or accelerating admixtures containing calcium chloride. Higher compressive strengths may be achieved by using larger aggregates in lieu of increasing the cement content and corresponding water demand. Additional workability, if desired, may be obtained by including water-reducing or air-entraining admixtures. Concrete for slabs, flatwork, or pavement should have a slump of 4 inches or less, as evaluated by ASTM Standard C143, before admixtures are added. The slump should be checked at the site by a representative of Ninyo & Moore or other qualified materials testing laboratory prior to placement. Concrete should be placed in accordance with ACI Manual of Concrete Practice (MCP) and project specifications. Particular attention should be given to curing techniques and curing duration. Slabs that do not receive adequate curing have a more pronounced tendency to develop random shrinkage cracks and other defects. 28

33 9.6. Moisture Vapor Retarder The migration of moisture through slabs underlying enclosed spaces or overlain by moisture sensitive floor coverings should be limited by providing a moisture vapor retarding system between the subgrade soils and the bottom of slabs. We recommend that the moisture vapor retarding system consist of a 4-inch thick capillary break, overlain by a plastic membrane 15-mil thick with a 2-inch thick clean blotter sand cover over the membrane. The capillary break should be constructed of clean, open-graded crushed rock or angular gravel of ¾-inch nominal size. The plastic membrane should conform to the requirements in the latest version of ASTM Standard E 1745 for a Class A membrane. The blotter sand should be in a moist but not saturated condition prior to concrete placement. The bottom of the moisture barrier system should be higher in elevation than the exterior grade, if possible. Positive drainage should be established and maintained adjacent to foundations and flatwork. A subdrain should be constructed around the foundation perimeter at locations where the exterior grade is at a higher elevation than the moisture vapor retarding system (including the capillary break layer). The subdrain should consist of ¾-inch crushed rock wrapped in filter fabric (Mirafi 140N, or equivalent). The subdrain should be capped by a pavement or 12 inches of native soil and drained by a perforated pipe (Schedule 40 PVC pipe, or similar). The pipe should be sloped at 1 percent or more to discharge at an appropriate outlet away from the foundation. The pipe should be located below the bottom elevation of the moisture vapor retarding system but above a plane extending down and away from the bottom edge of the foundation at a 2:1 (horizontal to vertical) gradient Drainage and Site Maintenance Surface drainage on the site should generally be provided so that water is diverted away from structures and slopes and is not permitted to pond. Positive drainage consisting of a gradient of 2 percent or more should be established over the pad and for a distance of 5 feet or more adjacent to structures and sloped to divert surface water to an appropriate collector (graded swale, v-ditch, or area drain) with a suitable outlet. Roof, slope, and pad drainage 29

34 should be collected and diverted to suitable discharge areas away from structures or other slopes by non-erodible devices (e.g., gutters, downspouts, concrete swales, etc.). Graded swales, v-ditches, or curb and gutter should be provided at the site perimeter to restrict flow of surface water onto and off of the site. Drainage structures should be periodically cleaned out and repaired, as needed, to maintain appropriate site drainage patterns. Care should be taken by the contractor during grading to preserve any berms, drainage terraces, interceptor swales or other drainage devices on or adjacent to the property. Drainage patterns established at the time of grading should be maintained for the life of the project. The property owner and maintenance personnel should be made aware that altering drainage patterns might be detrimental to foundation performance. Landscaping adjacent to foundations should include vegetation with low-water demands and irrigation should be limited to that which is needed to sustain the plants. Trees should be restricted from the areas adjacent to foundations a distance equivalent to the canopy radius of the mature tree Review of Construction Plans The recommendations provided in this report are based on preliminary design information for the proposed construction. We recommend that the geotechnical consultant review project plans to check that the recommendations are suitable for the proposed construction and to check that our recommendations are appropriately interpreted and incorporated on the plans. It should be noted that upon review of these documents, some recommendations presented in this report might be revised or modified to meet the project requirements Pre-Construction Conference We recommend that a pre-construction conference be held. Owner representatives, the architect, the structural engineer, the civil engineer, the geotechnical consultant, and the contractor should be in attendance to discuss the plans, the project, and the proposed construction schedule. 30

35 9.10. Construction Observation and Testing The recommendations provided in this report are based on subsurface conditions disclosed by widely spaced exploratory borings. The geotechnical consultant in the field during construction should check the interpolated subsurface conditions. During construction, the geotechnical consultant should: Observe excavation of unsuitable materials. Check and test imported materials prior to their use as fill. Observe lime-treatment of on-site soils. Observe placement and compaction of fill. Perform field density tests to evaluate fill compaction. Observe slab subgrade and footing excavations for bearing materials and cleaning prior to placement of reinforcing steel and concrete. Observe condition of water vapor retarding system prior to concrete placement. The recommendations provided in this report assume that Ninyo & Moore will be retained as the geotechnical consultant during the construction phase of the project. If another geotechnical consultant is selected, we request that the selected consultant provide a letter to the architect and the owner (with a copy to Ninyo & Moore) indicating that they fully understand Ninyo & Moore s recommendations, and that they are in full agreement with the recommendations contained in this report. 10. LIMITATIONS The field evaluation, laboratory testing, engineering geology assessment, and geotechnical analyses presented in this geologic hazard and geotechnical evaluation report have been conducted in general accordance with current practice and the standard of care exercised by geologic and geotechnical consultants performing similar tasks in the project area. No warranty, expressed or implied, is made regarding the conclusions, recommendations, and opinions presented in this report. There is no evaluation detailed enough to reveal every subsurface condition. Variations may 31

36 exist and conditions not observed or described in this report may be encountered during construction. Uncertainties relative to subsurface conditions can be reduced through additional subsurface exploration. Additional subsurface evaluation will be performed upon request. Please also note that our evaluation was limited to assessment of the geotechnical aspects of the project, and did not include evaluation of structural issues, environmental concerns, or the presence of hazardous materials. This document is intended to be used only in its entirety. No portion of the document, by itself, is designed to completely represent any aspect of the project described herein. Ninyo & Moore should be contacted if the reader requires additional information or has questions regarding the content, interpretations presented, or completeness of this document. This report is intended for design purposes only. It does not provide sufficient data to prepare an accurate bid by contractors. It is suggested that the bidders and their geotechnical consultant perform an independent evaluation of the subsurface conditions in the project areas. The independent evaluations may include, but not be limited to, review of other geotechnical reports prepared for the adjacent areas, site reconnaissance, and additional exploration and laboratory testing. Our conclusions, recommendations, and opinions are based on an analysis of the observed site conditions. If geotechnical conditions different from those described in this report are encountered, our office should be notified, and additional recommendations, if warranted, will be provided upon request. It should be understood that the conditions of a site could change with time as a result of natural processes or the activities of man at the subject site or nearby sites. In addition, changes to the applicable laws, regulations, codes, and standards of practice may occur due to government action or the broadening of knowledge. The findings of this report may, therefore, be invalidated over time, in part or in whole, by changes over which Ninyo & Moore has no control. 32

37 This report is intended exclusively for use by the client. Any use or reuse of the findings, conclusions, and/or recommendations of this report by parties other than the client is undertaken at said parties sole risk. 33

38 11. REFERENCES American Concrete Institute (ACI), 2012, ACI Manual of Concrete Practice. American Society of Civil Engineers (ASCE), 2010, Minimum Design Loads for Buildings and Other Structures, Reston, Virginia. American Society for Testing and Materials (ASTM), 2013, Annual Book of ASTM Standards, West Conshohocken, Pennsylvania. Association of Bay Area Governments (ABAG), 1995, Hazard Map, Dam Failure Inundation Areas; available online at Association of Bay Area Governments (ABAG), 2009, Tsunami Evacuation Planning Map; available online at Bray, J.D., and Sancio, R.B., 2006, Assessment of the Liquefaction Susceptibility of Fine- Grained Soils, Journal of Geotechnical and Geoenvironmental Engineering, American Society of Civil Engineers (ASCE), Vol. 132, No. 9, pp California Building Standards Commission (CBSC), 2013, California Building Code (CBC), Title 24, Part 2, Volumes 1 and 2. California Department of Transportation (Caltrans), 2012, Corrosion Guidelines, Version 2.0, Division of Engineering Services, Materials Engineering and Testing Services, Corrosion Technology Branch: dated November. California Division of Mines and Geology (CDMG), 1980, California Geology: The Livermore Earthquake of January 1980, Contra Costa and Alameda Counties, California, April 1980, Volume 33, No. 4. California Division of Mines and Geology, 1982, State of California Special Studies Zones, Livermore Quadrangle: dated January 1: scale 1:24,000. California Geological Survey, 2013a, Note 48, Checklist for Review of Engineering Geology and Seismology Reports for California Public Schools, Hospitals, and Essential Services Buildings: dated October. California Geological Survey, 2013b, California Historical Earthquakes (M>5.5), World Wide Web, California Geological Survey, 2008a, Seismic Hazard Zone Report for the Livermore 7.5-Minute Quadrangle, Alameda County, California, Seismic Hazard Zone Report 114. California Geological Survey, 2008b, Seismic Hazard Zone Map for the Livermore 7.5-Minute Quadrangle, Alameda County, California, Scale: 1:24,000, dated August

39 Cao, T., Bryant, W.A., Rowshandel, B., Branum, D., and Wills, C. J., 2003, The revised 2002 California Probabilistic Seismic Hazard Maps, California, USGS/CGS: dated June. Crane, R.C., 1995, Geology of Mount Diablo Region and East Bay Hills; in Recent Geological Studies of the San Francisco Bay Area, SEPM, Pacific Section, Vol. 76, p : scale 1:24,000. Division of the State Architect (DSA), California Department of General Services, 2013, Geologic Hazard Report Requirements, Interpretation of Regulations Document IR A-4: revised December 19. Dibblee, T.W., 2006, Geologic Map of the Livermore Quadrangle, Contra Costa and Alameda Counties, California: scale 1:24,000; Dibblee Geology Center Map #DF-196. Federal Emergency Management Agency (FEMA), 2009, Flood Insurance Rate Map, Alameda County, California, Panel 333 of 725, Map Number 06001C0333G, dated August 3. Google Earth, 2013, Google Earth 6.2.2, Graymer, R.W., Jones, D.L., and Brabb, E.E., 1996, Preliminary Geologic Map Emphasizing Bedrock Formations in Alameda County, California, USGS, OFR , scale 1:75:000. Herd, D.G., 1977, Geologic Map of the Las Positas, Greenville, and Verona Faults, Eastern Alameda County, California, USGS OFR : Scale 1:24,000. Jennings, C.W. and Bryant, W.A, 2010, Fault Activity Map of California and Adjacent Areas: California Geological Survey, California Geologic Data Map Series, Map No. 6, Scale 1:750,000. Majmunder, H., 1991, Landslide Hazards in the Livermore Valley and Vicinity, Alameda and Contra Costa Counties, California: CDMG Landslide Hazard Identification Map 21 DMG OFR 91-2: scale 1:24,000. Ninyo & Moore, 2007a, Potential Fault Evaluation Study, Las Positas Community College, Livermore, California: Project No : dated August 24. Ninyo & Moore, 2007b, Geologic Hazards Assessment and Geotechnical Evaluation, Child Development Center, Las Positas College, Livermore, California: Project No : dated November 1. Ninyo & Moore, 2008, Geologic Hazards Assessment and Geotechnical Evaluation, Student and Administrative Services Building, Las Positas College, Livermore, California: Project No : dated June 17. Ninyo & Moore, 2009a, Geologic Hazards Assessment and Geotechnical Evaluation, Science Technology Phase II, Las Positas College, Livermore, California: Project No : dated June

40 Ninyo & Moore, 2009b, Geologic Hazards Assessment and Geotechnical Evaluation, Student and Administrative Services Building, Las Positas College, Livermore, California: Project No : dated November 3. Occupational Safety and Health Administration (OSHA), 1989, Occupational Safety and Health Standards Excavations, Department of Labor, Title 29 Code of Federal Regulations (CFR) part 1926, dated October 31. Scheimer, J.F., Taylor, S.R., and Sharp, M., 1982, Seismicity of the Livermore Valley Region, ; in Hart, E.W., Hirschfeld, S.E., Schulz, S.S., 1982, Proceedings: Conference on Earthquake Hazards in the Eastern San Francisco Bay Area: CDMG Special Publication 62. United States Geological Survey, 2012, Earthquake Hazards Program, Historic Earthquakes, United States Geological Survey, 2013, United States Seismic Design Maps, World Wide Web, United States Geological Survey, 2014, National Earthquake Information Center - NEIC, World Wide Web, 36

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43 SITE REFERENCE: GRAYMER, R.W., JONES, D.L. & BRABB, E.E, 1996, PRELIMINARY GEOLOGIC MAP EMPHASIZING BEDROCK FORMATIONS IN ALAMEDA COUNTY, CALIFORNIA, UNITED STATES GEOLOGICAL SURVEY OFR ; SCALE 1:175,000. LEGEND N Qu QTI SURFICIAL DEPOSITS, UNDIVIDED LIVERMORE GRAVELS SCALE IN FEET 0 6,250 12,500 NOTE: ALL DIMENSIONS, DIRECTIONS AND LOCATIONS ARE APPROXIMATE. Tgvt Tn Tc GREEN VALLEY AND TASSAJARA FORMATIONS, UNDIVIDED NEROLY FORMATION - BLUE SANDSTONE CIERBO FORMATION - WHITE SANDSTONE PROJECT NO. DATE /14 REGIONAL GEOLOGY NEW ACADEMIC BUILDING LAS POSITAS COLLEGE LIVERMORE, CALIFORNIA FIGURE 3

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46 M A A C A M A B A R T L E T T S P R I N G S Oroville CALIFORNIA Ukiah Yuba City K O N O C T I B AY C O L L O AY O M I Clearlake Highlands H U N T I N G C R E E K - B E R R Y E S S A Woodland R O D G E R S C R E E K Davis Sacramento Santa Rosa W E S T N A PA S A N A N D R E A S Fairfield Novato Vallejo PACIFIC OCEAN H AY W A R D G R E E N V A L L E Y Concord Lodi Stockton San Francisco San Mateo Hayward Santa Cruz C A L AV E R A S G R E E N V I L L E S O U T H E A S T E X T E N S I O N San Jose Livermore S A R G E A N T Watsonville Morgan Hill SITE Manteca O R T I G A L I TA Modesto Oakdale FOOTHILLS FAULT SYSTEM Atwater Merced M O N T E R E Y B AY - T U L A R C I T O S S A N G R E G O R I O Hollister Q U I E N S A B E Madera Seaside Salinas R E L I Z F A U LT Z O N E S A N A N D R E A S SOURCE: Fault Activity Map of California, 2010, Jennings, C.W., and Bryant, W.A., California Geological Survey. C:\GIS\DATA\fault_loc_2010_OAK\fault_loc_2010_OAK_92.mxd APPROXIMATE SCALE MILES NOTES: ALL DIRECTIONS, DIMENSIONS AND LOCATIONS ARE APPROXIMATE PROJECT NO. DATE /14 LEGEND CALIFORNIA FAULT ACTIVITY HISTORICALLY ACTIVE HOLOCENE ACTIVE STATE/COUNTY BOUNDARY FAULT LOCATIONS NEW ACADEMIC BUILDING LAS POSITAS COLLEGE LIVERMORE, CALIFORNIA QUATERNARY (POTENTIALLY ACTIVE) LATE QUATERNARY (POTENTIALLY ACTIVE) FIGURE 6