GEOTECHNICAL INVESTIGATION

Transcription

1 GEOTECHNICAL INVESTIGATION Soquel Drive, Santa Cruz County, California Submitted to: Soquel Creek Water District P.O. Box 1550 Capitola, California Prepared by: CMAG ENGINEERING, INC. August 23, 2012

2 CMAG ENGINEERING, INC WINKLE AVENUE, SANTA CRUZ, CALIFORNIA PHONE: FAX: Soquel Creek Water District P.O. Box 1550 Capitola, California ATTN: Taj A. Dufour, PE August 23, 2012 SUBJECT: GEOTECHNICAL INVESTIGATION Preliminary Design Phase Proposed Well / Treatment Plant O Neill Ranch, CWO Soquel Drive, Soquel, Santa Cruz County, California APN , 12 Dear Mr. Dufour: CMAG Engineering, Inc. has been retained by the Soquel Creek Water District to provide a geotechnical investigation report for the proposed O Neill Ranch well and treatment plant located off of Soquel Drive in Santa Cruz County, California. Our investigation included surface and subsurface field exploration programs, laboratory testing, and engineering analysis. The proposed building envelope is located on a gently sloping portion of the site, however, a moderate slope descends to the north, on the north side of the proposed facility. A drainage exists at the base of the slope and the northern property line. The banks of the drainage are steep and have been subject to minor shallow failures. The subsurface profile in the location of the proposed structures consists of approximately 20 feet of dense to very dense silty sands overlying Purisima Formation bedrock. A thin veneer of moderately expansive sandy lean clay caps the silty sands. We performed a quantitative slope stability analysis. The calculated factors of safety met industry standards under static and seismic conditions. The failures observed on the banks of the drainage, in our opinion, are a result of erosion and not landsliding. Weak soils, accumulated near the base of the slope, are subject to gully erosion from surface runoff. It is our opinion that there is a high potential for erosion to occur at the base of the slope due to surface runoff and the meandering drainage. We have provided recommendations to help control surface runoff.

3 Geotechnical Investigation August 23, 2012 Santa Cruz County, California Page ii We have provided recommendations for seismic design, general site grading, site drainage, shallow foundations, slabs-on-grade, retaining walls, and pavements. This summary omits detailed recommendations; therefore, anyone relying on the report should read it in its entirety. It is a pleasure being associated with you on this project. If you have any questions, or if we may be of further assistance, please do not hesitate to contact our office. Sincerely, CMAG ENGINEERING, INC. Adrian L. Garner, PE, GE Principal Engineer C 66087, GE 2814 Expires 6/30/14 Distribution: Addressee (4 Hard Copies; Electronic Copy)

4 Geotechnical Investigation August 23, 2012 Santa Cruz County, California Page iii TABLE OF CONTENTS 1.0 INTRODUCTION Terms of Reference Site Conditions Project Description GEOLOGIC SETTING AND SEISMICITY Geologic Setting Regional Seismicity and Faulting FIELD EXPLORATION AND LABORATORY TESTING PROGRAMS SUBSURFACE CONDITIONS AND EARTH MATERIALS General Purisima Formation - Tp Lowest Emergent Coastal Terrace Deposits - Qcl Surficial Soil (Topsoil) Colluvium - Qtl Groundwater GEOTECHNICAL HAZARDS General Seismic Shaking USGS PSHA CBC Design Ground Motion Parameters Collateral Seismic Hazards Slope Stability General Analysis Material Properties and Groundwater Modeling Analysis Results Discussion Erosion General Gullies DISCUSSIONS AND CONCLUSIONS RECOMMENDATIONS General Site Grading Site Clearing Preparation of On-Site Soils Utility Trenches... 13

5 Geotechnical Investigation August 23, 2012 Santa Cruz County, California Page iv Excavating Conditions Surface Drainage Foundations Conventional Shallow Foundations Concrete Slabs-on-Grade Settlements Retaining Structures General Lateral Pressures Due to Earthquake Motions Lateral Earth Pressures Backfill Backfill Drainage Flexible Pavements Plan Review Observation and Testing LIMITATIONS TABLES Table 1. Regional Active Faults... 3 Table 2. PGA USGS PSHA... 6 Table 3. Spectral Accelerations CBC Table 4. Material Properties... 8 Table 5. Summary of Calculated Factors of Safety... 9 Table 6. Lateral Earth Pressures Table 7. Flexible Pavement Sections FIGURES Figure 1: Site Location Map Figure 2: Local Geologic Map Figure 3: Quaternary Faults Figure 4: Surcharge Pressure Diagram Figure 5: Typical Backdrain Detail APPENDICES APPENDIX A Field Exploration Program APPENDIX B Laboratory Testing Program APPENDIX C Slope Stability Results

6 Geotechnical Investigation August 23, 2012 Santa Cruz County, California Page INTRODUCTION CMAG Engineering, Inc. (CMAG) has been retained by the Soquel Creek Water District (SCWD) to provide a geotechnical investigation report for the construction of a well and treatment plant located on the northeast corner of 41 st Avenue and Soquel Drive in Santa Cruz County, California. This report presents the results of our geotechnical investigation and presents preliminary design recommendations based on our field investigation, laboratory testing, and engineering analysis. 1.1 Terms of Reference CMAG s scope of work for this phase of the project included review of existing information, field exploration, laboratory testing, and engineering analysis to provide a geotechnical investigation report. The work has been undertaken in accordance with the Soquel Creek Water District Contract for Services dated May 9, The recommendations contained in this report are subject to the limitations presented in Section 8.0 of this report. 1.2 Site Conditions The project site is located north of the city limits of Capitola in unincorporated Santa Cruz County, California. The site is bound by Soquel Drive to the south and a drainage to the north. The parcels, APN and 12, sum approximately 1.6 acres. The site location is shown on the Site Location Map, Figure 1. The proposed building site is situated on a gentle slope, descending to the north. The slope becomes moderate to the north of the proposed building envelope. The banks descending to the drainage are steep. Small scale failures were observed on the banks of the drainage. A failure on the northwest side of the parcel extends beyond the creek bank and into the moderate slope. The site, adjacent to Soquel Drive, is vegetated with grass. The northern portion of the site is vegetated with trees and brush. 1.3 Project Description The components of the plant consist of a well and control building, a backwash reservoir, pressure tanks, and a filter pad. The anticipated construction of the well and control building consists of a CMU building founded on conventional shallow foundations with a concrete slab-on-grade. The pressure vessels and filter tanks are proposed to be founded on slab-on-grade foundations. The backwash reservoir

7 Geotechnical Investigation August 23, 2012 Santa Cruz County, California Page 2 is founded below grade, requiring retaining walls and a concrete slab. A paved access driveway is also anticipated. 2.1 Geologic Setting 2.0 GEOLOGIC SETTING AND SEISMICITY The project site is located in the central Santa Cruz Mountains in the geomorphic province of the California Coast Ranges. The Santa Cruz Mountains are generally underlain by granitic and metamorphic basement rocks of the Salinian Block. Overlying the basement rocks is a sequence of Tertiary sedimentary rock ranging in age from Paleocene to Pliocene. Tectonic forces from the collision of the North American and Pacific Plates have produced the northwest trending ridges and parallel valleys in the area. The project site has been mapped by Earl E. Brabb (1997) as underlain by the Lowest Emergent Coastal Terrace Deposits (Qcl; Pleistocene) and Colluvium (Qtl; Holocene). The colluvium is mapped on the northern portion of the site, with the contact at the crest of the slope. Colluvium is a general term applied to loose deposits, accumulated by the action of gravity. Tertiary sedimentary rocks (Brabb E.E., 1997) of the Purisima Formation (Tp; Pliocene and upper Miocene) have been mapped to the north of the site. See Figure 2 for a local geologic map of the area. 2.2 Regional Seismicity and Faulting The 2007 Working Group on California Earthquake Probabilities (2007 WGCEP) at the U.S. Geological Survey (USGS) developed estimates of earthquake probabilities in the San Francisco Bay area. The 2007 WGCEP estimates a probability of 63 percent of a magnitude 6.7 or larger earthquake striking the San Francisco Bay area over the next 30 years. The major active faults in the area are the Zayante - Vergeles Fault Zone, the San Andreas Fault Zone, the Monterey Bay - Tularcitos Fault Zone, and the San Gregorio Fault Zone. A probability of a magnitude 6.7 or larger earthquake on the N. San Andreas Fault Zone is predicted by the 2007 WGCEP to be 21 percent over the next 30 years. The USGS has published national seismic hazard maps displaying earthquake ground motions for various probability levels across the United States. The approximate distances to the active faults from the site and the estimated Mean Characteristic Moment Magnitude are presented in Table 1. The distance to the faults and the Mean Characteristic Moment Magnitude were determined from the USGS 2008 National Seismic Hazard Maps (NSHMP) model. A latitude and longitude of degrees and degrees, respectively was used for our spatial query.

8 Geotechnical Investigation August 23, 2012 Santa Cruz County, California Page 3 Fault Segment Table 1. Regional Active Faults Approximate Distance to Site (km) Mean Characteristic Moment Magnitude Zayante -Vergeles N. San Andreas; SAN+SAP+SAS N. San Andreas; SAO+SAN+SAP+SAS N. San Andreas; SAP+SAS N. San Andreas; SAS N. San Andreas; SAN+SAP N. San Andreas; SAO+SAN+SAP N. San Andreas; SAP Monterey Bay - Tularcitos San Gregorio Connected See Figure 3 for a map depicting faults that are believed to be sources of earthquakes greater than Magnitude 6 within the Quaternary (past 1.6 million years). The faults presented in Table 1 have been labeled on Figure FIELD EXPLORATION AND LABORATORY TESTING PROGRAMS Our field exploration program included drilling, logging, and interval sampling of 5 borings on June 13, The borings were advanced to depths ranging from 10+ feet to feet below existing grades. Details of the field exploration program, including the Boring Logs, Figures A-3 through A-7, are presented in Appendix A. Representative samples obtained during the field investigation were taken to the laboratory for testing to determine physical and engineering properties. Details of the laboratory testing program are presented in Appendix B. Test results are presented on the Boring Logs and in Appendix B.

9 Geotechnical Investigation August 23, 2012 Santa Cruz County, California Page General 4.0 SUBSURFACE CONDITIONS AND EARTH MATERIALS Five borings were advanced in the vicinity of the proposed well / treatment plant and paved access driveway. The mapped geologic units that we encountered in our borings consisted of the Lowest Emergent Coastal Terrace Deposits (Qcl; Pleistocene) and Purisima Formation (Tp; Pliocene and upper Miocene). The colluvium, mapped on the northern portion of the site was not encountered within our borings. Colluvium was observed within the small failures observed adjacent to the drainage on the northern side of the site. Complete soil profiles are presented on the Boring Logs, Appendix A, Figures A-3 through A-7. A representative cross section was obtained for the subject site. See Cross Section A-A on Figure A-8. The boring locations and the location of the cross section are shown on the Boring Location Plan, Figure A Purisima Formation - Tp The Purisima Formation was encountered in Borings B-4 and B-5, at depths of approximately 19 and 25 feet below existing grade, respectively. The bedrock generally consisted of very dense poorly graded sandstone. 4.3 Lowest Emergent Coastal Terrace Deposits - Qcl Lowest Emergent Coastal Terrace Deposits were encountered within all the borings advanced for our field exploration. In general, the deposits consisted of dense to very dense silty sands with varying amounts of gravel. The Lowest Emergent Coastal Terrace Deposits were encountered beneath the surficial soil and overlying the Purisima Formation bedrock. 4.4 Surficial Soil (Topsoil) A thin veneer of topsoil was encountered in the borings above the terrace deposits. In general, the topsoil consisted of hard sandy lean clay. The topsoil varied from approximately 2 to 3 feet thick. The results of our laboratory testing indicate that the sandy lean clay has a moderate expansion potential. 4.5 Colluvium - Qtl Colluvium, consisting of silty and clayey sand with clasts of sandstone was observed within the minor failures adjacent to the drainage. Colluvium was not encountered within the borings advanced for our field exploration.

10 Geotechnical Investigation August 23, 2012 Santa Cruz County, California Page Groundwater Groundwater was not encountered within the borings advanced for our field exploration. However, during our site visit in April of 2012, seepage was noted at the head of the failure that extends upslope of the creek bank. It is our opinion that the seepage surface is a result of perched groundwater on the underlying Purisima Formation bedrock. The location of the seepage surface is consistent with the results of our subsurface investigation. Based on our experience in the vicinity, during the rainy season, surface water migrates through the terrace deposits and perches on the underlying bedrock. See Cross Section A-A, Figure A-8 for more information. It should be noted that groundwater conditions, perched or regional, may vary with location and may fluctuate with variations in rainfall, runoff, irrigation, and other changes to the conditions existing at the time our field investigation was performed. 5.1 General 5.0 GEOTECHNICAL HAZARDS In our opinion, the geotechnical hazards that could potentially affect the subject site are: 5.2 Seismic Shaking Intense seismic shaking Landsliding Erosion Intense seismic shaking is expected to occur at the site from a major earthquake along one of the local fault systems. Generally, the intensity of shaking will increase the closer the site is to the epicenter of an earthquake, however, seismic shaking is a complex phenomenon and may be modified by local topography and subsurface soil and bedrock conditions. To characterize the ground shaking hazard at the site, we used the USGS 2002 seismic hazard maps. We determined peak horizontal ground accelerations (PGA) from the USGS Probabalistic Seismic Hazard Analysis (PSHA) models. We also determined spectral accelerations based on the 2010 California Building Code (CBC 2010). For our determination of the ground motions, we used a site latitude and longitude of degrees and degrees, respectively.

11 Geotechnical Investigation August 23, 2012 Santa Cruz County, California Page USGS PSHA We determined the PGAs using the USGS 2002 NSHMP PSHA Interactive Deaggregations online seismic tool. PGAs have been established for three different return periods that correspond to 2 percent, 5 percent, and 10 percent exceedance in 50 years. The input parameters for the online tool consist of the site latitude and longitude. Table 2. PGA USGS PSHA Return Period (Chance of Exceedance) 2,475 Years (2% in 50 Years) 975 Years (5% in 50 Years) 475 Years (10% in 50 Years) PGA - Rock Site Condition (V S30 = 760 m/s) 0.67g 0.54g 0.43g CBC 2010 Spectral accelerations were determined in accordance with the CBC 2010 using the USGS U.S. National Maps Web Application online tool. The CBC 2010 incorporates the 2002 National Seismic Hazard Maps. The input parameters for the online tool consist of the site latitude and longitude and Site Class. A Site Class C was used for the site. Table 3. Spectral Accelerations - CBC 2010 S S S 1 F a F v S MS S M1 S DS S D g 0.603g g 0.784g 1.000g 0.523g Design Ground Motion Parameters The event that we considered for our quantitative analysis of the collateral seismic hazards (seismically induced landsliding) consisted of a magnitude 7.9 on the San Andreas Fault at a distance of 13.5 km from the site generating a peak ground acceleration of 0.43g. The event is based on the USGS 2002 NSHMP PSHA for a 10 percent of exceedance in 50 years.

12 Geotechnical Investigation August 23, 2012 Santa Cruz County, California Page Collateral Seismic Hazards In addition to seismic shaking, other seismic hazards that may have an adverse affect to the site and/or the structure are: fault ground surface rupture, coseismic ground cracking, seismically induced liquefaction and lateral spreading, seismically induced differential compaction, seismically induced landsliding, and seismically induced inundation (tsunami and seiche). It is our opinion that the potential for collateral seismic hazards to affect the site, and to damage the proposed structures is low. A quantitative slope stability analysis, considering seismic effects is presented in Section Slope Stability General Our scope of services for this project includes a quantitative stability analysis of the slope descending to the north. The proposed development is located on a gentle slope, however, a moderate slope descends to the drainage on the north side of the building envelope. The banks descending to the drainage are steep. We performed an overall slope stability analysis of the subject slopes to determine if set back requirements or, if necessary, mitigation measures were required to stabilize the slope. Small scale failures were observed on the banks of the drainage. A failure on the northwest side of the parcel extends upslope of the creek bank and into the moderate slope. As indicated in Section 4.5, seepage was observed at the head of the failure. This failure was relatively shallow, within the surficial soils. The results of our field exploration are consistent with the geomorphology of the site. It is our opinion that the break in slope observed between the moderate slope and the steep drainage banks is due to the contact between the Purisima Formation bedrock and the overlying soils. In addition, based on the mapping by Earl E. Brabb (1997) and consistent with our field observations, colluvial deposits were exposed within the failures. Based on our subsurface and surface field observations, it is our opinion that the observed failures are due to erosion and not landsliding. We have provided a discussion on erosion in Section Analysis Quantitative slope stability analyses were completed for the existing slope, Cross Section A-A. See Figure A-1 for the location of the cross section and Figure A-8 for Cross Section A-A. The slopes were analyzed for both static and seismic conditions. To analyze the seismic stability of the cross section, we performed a pseudostatic analysis based on Special Publication 117A, Guidelines for Evaluating

13 Geotechnical Investigation August 23, 2012 Santa Cruz County, California Page 8 and Mitigating Seismic Hazards in California (2008). Our pseudostatic analysis was performed assuming a k eq of 0.275g. The k eq was determined using the ground motion parameters in Section The stability of the cross section was analyzed using the computer program STABL for Windows, Version 3.0 from Geotechnical Software Solutions, LLC. This program utilizes a limiting equilibrium method for determining the Factor of Safety against sliding on an assumed failure surface Material Properties and Groundwater Modeling Material properties chosen for these analyses are conservatively based on laboratory test results and on experience in the vicinity. Laboratory shear strength tests were performed under saturated conditions. We assumed a groundwater table, perched on the underlying Purisima Formation bedrock, for our analysis. The material properties used in our slope stability analyses are presented in Table 4. Table 4. Material Properties Material Type Wet Density (lbs/ft 3 ) Saturated Density (lbs/ft 3 ) Angle of Internal Friction ( ) Cohesion (lb/ft 2 ) Angle of Internal Friction ( ) Cohesion (lb/ft 2 ) Static Static Psuedo Pseudo Qcl Tp Analysis Results The results of our analysis are presented in Appendix C, Figures C-1 and C-2. A summary of the results are presented in Table 5.

14 Geotechnical Investigation August 23, 2012 Santa Cruz County, California Page 9 Table 5. Summary of Calculated Factors of Safety Figure Description Calculated F.S. Minimum Acceptable F.S. C-1 Cross Section A-A, Overall Stability, Static Case * C-2 Cross Section A-A, Overall Stability, Pseudostatic Case ** Notes: *Considered the minimum Industry standard Factor of Safety. ** Considered the minimum Factor of Safety for the pseudostatic analysis procedure outlined in Special Publication 117A, Guidelines for Evaluating and Mitigating Seismic Hazards in California (2008) Discussion The results of our analysis indicate that the computed Factors of Safety for the existing slope configuration meet the minimum industry standards. It must be cautioned that slope stability analysis is an inexact science; and that the mathematical models of the slopes, rocks, and soils contain many simplifying assumptions, not the least of which is homogeneity. Density, moisture content and shear strength may vary within a soil or rock type. There may be localized areas of low strength within a soil or rock. Slope stability analyses and the generated factors of safety should be used as indicating trendlines. A slope with a safety factor less than one will not necessarily fail, but the probability of slope movement will be greater than a slope with a higher safety factor. Conversely, a slope with a safety factor greater than one may fail, but the probability of stability is higher than a slope with a lower safety factor. 5.5 Erosion General Denudation is the long-term sum of processes that cause the wearing away of the earth s surface leading to a reduction in elevation and relief of landforms and landscapes through erosion, weathering, and mass wasting. Mass wasting is the downslope movement of soil or rock without the direct aid of water or wind. Whereas erosion is the process of detachment, entrainment, transport, and deposition of soil and rock under the direct influence of water or wind. Weathering is the physical and chemical break down of rocks and soils due to exposure to the atmosphere without transportation.

15 Geotechnical Investigation August 23, 2012 Santa Cruz County, California Page 10 Our scope of services for this project includes analyzing the potential for mass wasting (landsliding) to occur on the slope descending to the north of the proposed development. However, these processes are not independent, and we have provided a discussion on erosion and the relation to mass wasting below Gullies The failures observed on the banks of the drainage are consistent with the geomorphologic process of a weak colluvial soil overlying dense bedrock adjacent to a meandering drainage. The thin blanket of colluvium deposited over the steep bedrock surface is subject to gully erosion from surficial runoff. In addition, the combination of the seepage forces due to the underlying low permeability bedrock combined with the down-cutting meandering drainage result in the observed failures. In general, the failures can be classified as gullies, head-cutting upslope. It is our opinion that this statement is also valid for the failure on the northwest side of the parcel; the gully has advanced upslope beyond the creek banks. It is our opinion that there is a high potential for gullies, due to the conditions described above, to continue to occur at the base of the slope adjacent to the drainage. We have provided mitigation recommendations in Section 7. If the gullies were to continue eroding the base of the slope adjacent to the creek, the geomorphic process may change to mass wasting in the form of small slump failures. This is due to loss of toe support and loss of lateral confinement. Based on our evaluation, it is our opinion that if significant erosion were to occur due to gullying or hydraulic scour, there is a low probability for failures (landsliding or slumping) to extend to the building envelope. It is our opinion that the failures would be relatively shallow, within the colluvium at the base of the slope. 6.0 DISCUSSIONS AND CONCLUSIONS Based on the results of our field exploration, the subsurface profile consists of Lowest Emergent Coastal Terrace Deposits overlying Purisima Formation bedrock. Colluvial deposits were observed to the north of the proposed building envelope adjacent to the drainage. The Lowest Emergent Coastal Terrace Deposits within the building envelope were generally dense to very dense. Purisima Formation bedrock was encountered at depths varying from 19 to 25 feet below existing grades. A thin veneer of hard sandy lean clay, approximately 2 to 3 feet thick was encountered above the terrace deposits. The results of our laboratory testing indicate that the sandy lean clay has a moderate expansion potential. Groundwater was not encountered during our drilling program, however, it is our opinion that groundwater will perch on the underlying bedrock during the rainy season.

16 Geotechnical Investigation August 23, 2012 Santa Cruz County, California Page 11 The results of our slope stability analysis indicate that the overall stability of the slope descending to the drainage on the northern portion of the site meets industry standards. Erosional gullies were observed at the base of the slope adjacent to the drainage. It is our opinion that there is a high potential for gullies to continue to occur. We have provided recommendations in this report to help control erosion due to surface runoff, however, we have not analyzed the potential for erosion and scour of the banks due to the meandering drainage. 7.1 General 7.0 RECOMMENDATIONS Based on the results of our field investigation, laboratory testing, and engineering analysis, it is our opinion that from the geotechnical standpoint, the subject site will be suitable for the proposed development provided the recommendations presented herein are implemented during grading and construction. It is our opinion that shallow foundation systems are suitable to support the proposed structures. It is our understanding that concrete slabs are proposed to support a portion of the well / treatment plant facilities. We have provided recommendations for conventional shallow foundations and concrete slabs in Section 7.3. To alleviate the potential for differential settlements / movements due to the sandy lean clay encountered in the upper 2 to 3 feet, we recommend site preparation consisting of overexcavation and replacement with compacted engineered fill per Subsection It is our understanding that the construction of the backwash reservoir will generate significant fill. The on-site soils, with the exception of the sandy lean clay, are suitable for use as engineered fill. To help control the erosion at the base of the slope adjacent to the meandering drainage, we have provided recommendations for surface drainage in Section Site Grading Site Clearing Prior to grading, the areas to be developed for structures, pavements and other improvements, should be stripped of any vegetation and cleared of any surface or subsurface obstructions, including any existing foundations, utility lines, basements, septic tanks, pavements, stockpiled fills, and miscellaneous debris. Surface vegetation and organically contaminated topsoil should be removed from areas to be graded.

17 Geotechnical Investigation August 23, 2012 Santa Cruz County, California Page 12 Holes resulting from the removal of buried obstructions that extend below finished site grades should be backfilled with compacted engineered fill compacted to the requirements of Subsection Preparation of On-Site Soils The results of our field investigation and laboratory testing indicate that the upper 2 to 3 feet of soil is composed of moderately expansive sandy lean clay. In order to ensure uniform compression characteristics and to obviate any potential for differential settlements or movements, site preparation, consisting of overexcavation and recompaction will be required prior to placement of conventional shallow foundations, concrete slabs-on-grade, drive areas, and new fills. The depths of overexcavation and recompaction recommended herein are subject to review during grading. For conventional shallow foundations, the native soil should be overexcavated a minimum of 1.5 feet below the bottom of the footing, or 2 feet below existing grade, whichever is greater. The exposed surface should then be scarified, moisture conditioned, and compacted to a minimum of 90 percent relative compaction. The material which was removed should then be replaced with engineered fill compacted to a minimum of 90 percent relative compaction. This zone of reworking shall extend a minimum of 5 feet laterally beyond the conventional shallow foundation footprint. For concrete slabs-on-grade, the native soil should be overexcavated a minimum of 1 foot below the bottom of the crushed rock, or 2 feet below existing grade, whichever is greater. The exposed surface should then be scarified, moisture conditioned, and compacted to a minimum of 90 percent relative compaction. The material which was removed should then be replaced with engineered fill compacted to a minimum of 90 percent relative compaction. This zone of reworking shall extend a minimum of 5 feet laterally beyond the concrete slabs-on-grade. Beneath the backwash reservoir, (foundations and concrete slabs), the bottom of the excavation should be scarified 6 inches, moisture conditioned, and compacted to 90 percent relative compaction. Beneath flexible pavements, the native soil should be overexcavated to a minimum of 1 foot below the bottom of the aggregate base course, or 2 feet below existing grade, whichever is greater. The exposed surface should then be scarified, moisture conditioned, and compacted to a minimum of 90 percent relative compaction. The material which was removed should then be replaced as engineered fill compacted to a minimum of 90 percent relative compaction. The upper 6 inches of subgrade and all aggregate base beneath flexible pavements shall be compacted to achieve a minimum relative compaction of 95 percent. This zone of reworking should extend laterally a minimum of 2 feet beyond the pavements.

18 Geotechnical Investigation August 23, 2012 Santa Cruz County, California Page 13 The on-site soils, with the exception of the sandy lean clay, may be used as engineered fill. The material should be verified by a representative of CMAG Engineering, Inc. in the field during grading operations. All soils, both existing onsite and imported, to be used as fill, should contain less than 3 percent organics and be free of debris and gravel over 2.5 inches in maximum dimension. All fill should be compacted with heavy vibratory equipment. Fill should be compacted by mechanical means in uniform horizontal loose lifts not exceeding 8 inches in thickness. The relative compaction and required moisture content shall be based on the maximum dry density and optimum moisture content obtained in accordance with ASTM D1557. Imported fill material should be approved by a representative of CMAG Engineering, Inc. prior to importing. Soils having a significant expansion potential should not be used as imported fill. The Geotechnical Engineer should be notified not less than 5 working days in advance of placing any fill or base course material proposed for import. Each proposed source of import material should be sampled, tested, and approved by the Geotechnical Engineer prior to delivery of any soils imported for use on the site. Any surface or subsurface obstruction, or questionable material encountered during grading, should be brought immediately to the attention of the Geotechnical Engineer for proper processing as required Utility Trenches Bedding material should consist of sand with SE not less than 30 which may then be jetted. The on-site native soils, with the exception of the sandy lean clay, may be utilized for trench backfill. Imported fill should be free of organic material and gravel over 2.5 inches in diameter. If sand is used, a 3 foot concrete plug should be placed in each trench where it passes under the exterior footings. Backfill of all exterior and interior trenches should be placed in thin lifts and mechanically compacted to achieve a relative compaction of not less than 95 percent in paved areas and 90 percent in other areas per ASTM D1557. Care should be taken not to damage utility lines. Utility trenches that are parallel to the sides of a structure should be placed so that they do not extend below a line sloping down and away at an inclination of 2:1 (H:V) from the bottom outside edge of all footings. Trenches should be capped with 1.5+ feet of impermeable material. Import material must be approved by the Geotechnical Engineer prior to its use.

19 Geotechnical Investigation August 23, 2012 Santa Cruz County, California Page 14 Trenches must be shored as required by the local regulatory agency, the State Of California Division of Industrial Safety Construction Safety Orders, and Federal OSHA requirements Excavating Conditions We anticipate that excavation of the on-site soils may be accomplished with standard earthmoving and trenching equipment Surface Drainage Pad drainage should be designed to collect and direct surface water away from structures to approved drainage facilities. A minimum gradient of 2+ percent should be maintained and drainage should be directed toward approved swales or drainage facilities. Concentrations of surface water runoff should be handled by providing the necessary structures, paved ditches, catch basins, etc. Surface water should not be concentrated and discharged over the slope. Surface water should be collected and discharged at the base of the slope within the drainage. The location of the discharge point(s) should be reviewed by the Geotechnical Engineer during the civil design phase. Concrete V-Ditches may be placed on the slope to intercept runoff and help prevent gully erosion. Maintenance schedules should be implemented to clear ditches of silt and debris. All roof eaves should be guttered with the outlets from the downspouts provided with adequate capacity to carry the storm water away from the structure to reduce the possibility of soil saturation and erosion. Drainage patterns approved at the time of construction should be maintained throughout the life of the structures. The building and surface drainage facilities must not be altered nor any grading, filling, or excavation conducted in the area without prior review by the Geotechnical Engineer. Irrigation activities at the site should be controlled and reasonable. 7.3 Foundations Conventional Shallow Foundations We recommend that conventional shallow foundations be founded on compacted engineered fill per Subsection We have provided geotechnical foundation design parameters below based on use of on the on-site silty sand as engineered fill. In the event that footings are founded in structural fill consisting of imported materials, the design parameters presented below will depend on the type of these

20 Geotechnical Investigation August 23, 2012 Santa Cruz County, California Page 15 materials and should be re-evaluated. Footing widths should be based on the allowable bearing value but not less than 12 inches. The minimum recommended depth of embedment is 18 inches for exterior wall footings. Interior footings depths should be at least 12 inches. Embedment depths should not be allowed to be affected adversely, such as through erosion, softening, digging, etc. The allowable bearing capacity used should not exceed 2,800 psf. The allowable bearing capacity may be increased by one-third in the case of short duration loads, such as those induced by wind or seismic forces. A passive pressure of 280 psf/ft (equivalent fluid pressure) may be assumed for design purposes. Neglect passive pressure in the top 12 inches of soil. Passive pressures may be increased by one-third for seismic loading. A friction coefficient of 0.4 may be assumed for design purposes. Where both friction and the passive resistance are utilized for sliding resistance, either of the values indicated should be reduced by one-third. Footing excavations must be checked by the Geotechnical Engineer before steel reinforcement is placed and concrete is poured Concrete Slabs-on-Grade We recommend that concrete slab-on-grade be founded on compacted engineered fill per Subsection The subgrade should be proof-rolled just prior to construction to provide a firm, relatively unyielding surface, especially if the surface has been loosened by the passage of construction traffic. Concrete slabs may be designed assuming k s = 300 kcf. The slab-on-grade should be underlain by a minimum 4 inch thick capillary break of clean crushed rock. It is recommended that neither Class II baserock nor sand be employed as the capillary break material. Where moisture sensitive floor coverings are anticipated or vapor transmission may be a problem, a vapor retarder should be placed between the granular layer and the floor slab in order to reduce moisture condensation under the floor coverings. The vapor retarder should be specified by the slab designer. It should be noted that conventional slab-on-grade construction is not waterproof. Under-slab construction consisting of a capillary break and vapor retarder will not prevent moisture transmission through the slab-on-grade. CMAG Engineering, Inc. does not practice in the field of moisture vapor transmission evaluation or mitigation. Where moisture sensitive floor coverings are to be installed, a waterproofing expert should be consulted for their recommended moisture and vapor protection measures.

21 Geotechnical Investigation August 23, 2012 Santa Cruz County, California Page Settlements Total and differential settlements beneath conventional shallow foundations and concrete slabs are expected to be within tolerable limits. Vertical movements are not expected to exceed 1 inch. Differential movements are expected to be within the normal range (½ inch) for the anticipated loads and spacings. These preliminary estimates should be reviewed by the Geotechnical Engineer when foundation plans for the proposed structures become available. 7.4 Retaining Structures General Retaining walls may be founded on conventional shallow foundations per Subsection Lateral Pressure Due to Earthquake Motions For design purposes, the lateral force on retaining walls due to earthquake motions is 6H 2 lbs/horizontal foot, acting at a point 1/3H above the wall base, where H is the height of the wall in feet Lateral Earth Pressures The lateral earth pressures presented in Table 6 are recommended for the design of retaining structures with a gravel blanket and backfill soils of expansivity not higher than Medium. The values presented in Table 6 are based on the near surface silty sands. Soil Profile (H:V) Table 6. Lateral Earth Pressures Equivalent Fluid Pressure (psf/ft) Active Pressure At-Rest Pressure Level : : : Pressure due to any surcharge loads from adjacent footings, traffic, etc., should be analyzed separately. Pressures due to these loading can be supplied upon receipt of the appropriate plans and loads. Refer to Figure 4.

22 Geotechnical Investigation August 23, 2012 Santa Cruz County, California Page Backfill Backfill should be placed under engineering control. Backfill should be compacted per Subsection 7.2.2, however, precautions should be taken to ensure that heavy compaction equipment is not used immediately adjacent to walls, so as to prevent undue pressures against, and movement of, the walls. It is recommended that granular, or relatively low expansivity, backfill be utilized, for a width equal to approximately 1/3 times the wall height, and not less than 1.5 feet, subject to review during construction. The granular backfill should be capped with at least 12 inches of relatively impermeable material Backfill Drainage Backdrains should be provided in the backfill, or weepholes/weepslits should be provided in retaining walls. (It is recommended that backdrains be provided for walls over 4+ feet high, for retaining walls which form part of a building structure, and where any staining or efflorescence due to dripping from weepholes/weepslits would be aesthetically unacceptable.) Backdrains should consist of 4 inch diameter SDR 35 PVC perforated pipe or equivalent, embedded in 3/8 inch to 3/4 inch, clean crushed gravel, enveloped in Mirafi Filterweave 402 or approved equivalent. The drain should be a minimum of 18 inches in thickness and should extend to within 12 inches from the surface. The upper 12 inches should be capped with relatively impermeable material (the on-site sandy lean clay may be used). The pipe should be 4+ inches above the trench bottom; a gradient of 2+ percent being provided to the pipe and trench bottom; discharging into suitably protected outlets. See Figure 5 for the standard detail for the backdrain. Perforations in backdrains are recommended as follows: 3/8 inch diameter, in 2 rows at the ends of a 120 degree arc, at 3 inch centers in each row, staggered between rows, placed downward. Backdrains should be observed by the Geotechnical Engineer after placement of bedding and pipe and prior to the placement of clean crushed gravel. An unobstructed outlet should be provided at the lower end of each segment of backdrain. The outlet should consist of an unperforated pipe of the same diameter, connected to the perforated pipe and extended to a protected outlet at a lower elevation on a continuous gradient of at least 1 percent.

23 Geotechnical Investigation August 23, 2012 Santa Cruz County, California Page Flexible Pavements California Department of Transportation (Caltrans) flexible pavement design method was used to develop recommendations for asphalt pavement sections. Estimated traffic indices for various pavement loading conditions (Traffic Index) and a resistance value (R-Value) of the subgrade soils was used for our design. The range of traffic indices were based on engineering judgement and our understanding of the anticipated traffic. Laboratory testing of the soil subgrade was used to determine the design R-Value. Table 7 presents our pavement section recommendations for the existing (native) subgrade soils. Table 7. Flexible Pavement Sections Traffic Index 5.5 Traffic Index 6 Traffic Index 6.5 Asphalt (inches) Class 2 Aggregate Base (inches) The Class 2 Aggregate Base should conform to Section A of the current Caltrans Standard Specifications. The earthwork recommendations presented in Section should be adhered to for the compaction requirements of subgrade and aggregate base beneath flexible pavements. Pavements sections with alternative traffic indices can be supplied upon request. 7.6 Plan Review The recommendations presented in this report are based on preliminary design information for the proposed project and on the findings of our geotechnical investigation. When completed, the Grading Plans, Foundation Plans and design loads should be reviewed by CMAG Engineering, Inc. prior to submitting the plans and contract bidding. Additional field exploration and laboratory testing may be required upon review of the final project design plans. 7.7 Observation and Testing Field observation and testing must be provided by a representative of CMAG Engineering, Inc. to enable them to form an opinion regarding the adequacy of the site preparation, the adequacy of fill materials, and the extent to which the earthwork

24 Geotechnical Investigation August 23, 2012 Santa Cruz County, California Page 19 is performed in accordance with the geotechnical conditions present, the requirements of the regulating agencies, the project specifications, and the recommendations presented in this report. Any earthwork performed in connection with the subject project without the full knowledge of, and not under the direct observation of CMAG Engineering, Inc. will render the recommendations of this report invalid. CMAG Engineering, Inc. should be notified at least 5 working days prior to any site clearing or other earthwork operations on the subject project in order to observe the stripping and disposal of unsuitable materials and to ensure coordination with the grading contractor. During this period, a preconstruction meeting should be held on the site to discuss project specifications, observation and testing requirements and responsibilities, and scheduling. 8.0 LIMITATIONS The recommendations contained in this report are based on our field explorations, laboratory testing, and our understanding of the proposed construction. The subsurface data used in the preparation of this report was obtained from the borings drilled during our field investigation. Variation in soil, geologic, and groundwater conditions can vary significantly between sample locations. As in most projects, conditions revealed during construction excavation may be at variance with preliminary findings. If this occurs, the changed conditions must be evaluated by the Project Geotechnical Engineer and the Geologist, and revised recommendations be provided as required. In addition, if the scope of the proposed construction changes from the described in this report, our firm should also be notified. Our investigation was performed in accordance with the usual and current standards of the profession, as they relate to this and similar localities. No other warranty, expressed or implied, is provided as to the conclusions and professional advice presented in this report. This report is issued with the understanding that it is the responsibility of the Owner, or of his Representative, to ensure that the information and recommendations contained herein are brought to the attention of the Architect and Engineer for the project and incorporated into the plans, and that it is ensured that the Contractor and Subcontractors implement such recommendations in the field. The use of information contained in this report for bidding purposes should be done at the Contractor s option and risk. This firm does not practice or consult in the field of safety engineering. We do not direct the Contractor's operations, and we are not responsible for other than our own personnel on the site; therefore, the safety of others is the responsibility of the Contractor. The

25 Geotechnical Investigation August 23, 2012 Santa Cruz County, California Page 20 Contractor should notify the Owner if he considers any of the recommended actions presented herein to be unsafe. The findings of this report are considered valid as of the present date. However, changes in the conditions of a site can occur with the passage of time, whether they be due to natural events or to human activities on this or adjacent sites. In addition, changes in applicable or appropriate codes and standards may occur, whether they result from legislation or the broadening of knowledge. Accordingly, this report may become invalidated wholly or partially by changes outside our control. Therefore, this report is subject to review and revision as changed conditions are identified. The scope of our services mutually agreed upon did not include any environmental assessment or study for the presence of hazardous to toxic materials in the soil, surface water, or air, on or below or around the site. CMAG Engineering, Inc. is not a mold prevention consultant; none of our services performed in connection with the proposed project are for the purpose of mold prevention. Proper implementation of the recommendations conveyed in our reports will not itself be sufficient to prevent mold from growing in or on the structures involved. REFERENCES American Society of Civil Engineers (2005). Minimum Design Loads for Buildings and Other Structures. ASCE Standard Brabb, E.E. (1997). Geologic Map of Santa Cruz County, California: A Digital Database: U.S. Geological Survey Miscellaneous Investigation Series, Map I-1905, scale 1: California Department of Conservation, Division of Mines and Geology (1997). Guidelines for Evaluating and Mitigating Seismic Hazards in California. Special Publication 117, 74 pp. California Department of Conservation, California Geologic Survey (2008). Guidelines for Evaluating and Mitigating Seismic Hazards in California. Special Publication 117A, 98 pp. California Department of Transportation (2010). Standard Specifications. California Department of Transportation (2012). Highway Design Manual.

26 Geotechnical Investigation August 23, 2012 Santa Cruz County, California Page 21 Cao, T., Bryant, W.A., Rowshandel, B., Branum, D., and Will, C.J. (2003). The Revised 2002 California Probabilistic Seismic Hazard Maps. California Geologic Survey,44 pp. International Code Council (2010). California Building Code. Volume 2. Petersen, M.D., Bryant, W.A., Cramer, C.H., Cao, T., Reichle, M.S., Frankel, A.D., Lienkaemper, J.J., McCrory, P.A., and Schwartz, D.P. (1996). Probabilistic Seismic Hazard Assessment for the State of California. California Division of Mines and Geology, Open-File Report 96-08, and U.S. Geologic Survey, Open-File Report , 59 pp. Petersen, Mark D., Frankel, Arthur D., Harmsen, Stephen C., Mueller, Charles S., Haller, Kathleen M., Wheeler, Russell L., Wesson, Robert L., Zeng, Yuehua, Boyd, Oliver S., Perkins, David M., Luco, Nicolas, Field, Edward H., Wills, Chris J., and Rukstales, Kenneth S. (2008). Documentation for the 2008 Update of the United States National Seismic Hazard Maps. U.S. Geological Survey Open-File Report , 61 p. Soquel Creek Water District (2012)., CWO , Request for Geologic and Geotechnical Engineering Services. Soquel Creek Water District (May 9, 2012). Soquel Creek Water District Contract for Services, CWO , Request for Geologic and Geotechnical Engineering Services. Southern California Earthquake Center (2003). Recommended Procedures for Implementation of DMG Special Publication 117: Guidelines for Analyzing and Mitigating Landslide Hazards in California. U.S. Geological Survey (2003). USGS 2002 National Seismic Hazard Maps. ( U.S. Geological Survey (2008). USGS 2008 National Seismic Hazard Maps. ( U.S. Geological Survey (2012). U.S. Seismic Design Maps Web Application ( U.S. Geological Survey (2008). Interactive Deaggregations (

27 Geotechnical Investigation August 23, 2012 Santa Cruz County, California Page 22 U.S. Geological Survey (2008) National Seismic Hazard Maps - Fault Parameters. ( Working Group on California Earthquake Probabilities (2008). The Uniform California Earthquake Rupture Forecast, Version 2 (UCERF 2). U.S. Geological Survey, Open-File Report , California Geological Survey, Special Report 203.

28 FIGURES AND STANDARD DETAILS Site Location Map Figure 1 Local Geologic Map Figure 2 Quaternary Faults Figure 3 Surcharge Pressure Diagram Figure 4 Typical Backdrain Detail Figure 5

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30 SITE Tp

31 SA ZAYA NTE N - VER GELE S FAU AN LT ZO DR NE EA SF AU LT ZO N E SAN RIO GO GRE LT FAU O NEILL RANCH WELL / TREATMENT PLANT E ZON YBA EY ER NE NT ZO MO ULT FA S ITO RC LA TU

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34 APPENDIX A FIELD EXPLORATION PROGRAM Field Exploration Procedures Page A-1 Boring Location Plan Figure A-1 Key to the Logs Figure A-2 Logs of the Borings Figures A-3 through A-7 Cross Section A-A Figure A-8

35 Geotechnical Investigation August 23, 2012 Santa Cruz County, California Page A-1 FIELD EXPLORATION PROCEDURES Subsurface conditions were explored by drilling 5 borings to depths between 10+ and feet below the existing grade. Boring B-1 was drilled with a track mounted drill rig equipped with 4 inch diameter solid stem augers. Borings B-2 through B-5 were drilled with a truck mounted drill rig equipped with 6 inch diameter solid stem augers. The Key to The Logs and the Logs of the Borings are included in Appendix A, Figures A-2 through A-7. The approximate location of the borings are shown on the Boring Location Plan, Figure A-1. The soil and bedrock encountered in the borings were continuously logged in the field by a representative of CMAG Engineering, Inc. Bulk and relatively undisturbed soil and bedrock samples for identification and laboratory testing were obtained in the field. These soils and bedrock were classified based on field observations and laboratory tests. The classification is in accordance with the Unified Soil Classification System (Figure A-3). Representative soil and bedrock samples were obtained by means of a drive sampler, the hammer weight and drop being 140 lb and 30 inches, respectively. These samples were recovered using a 3 inch outside diameter Modified California Sampler or a 2 inch outside diameter Terzaghi Sampler. The number of blows required to drive the samplers 12 inches are indicated on the Boring Logs. The penetration test data for the Terzaghi driven samples has been presented as N 60 values. The N 60 values are also indicated on the Boring Logs. A representative cross section was obtained for the subject site. See Cross Section A-A, Figure A-8. For an explanation of the symbols and units on the cross section, see Section 3.3 of the report.

36 1

37 COARSE GRAINED SOILS More than half of the material is larger than the No. 200 sieve PRIMARY DIVISIONS GRAVELS More than half of the coarse fraction is larger than the No. 4 sieve SANDS More than half of the coarse fraction is smaller than the No. 4 sieve SAND WITH FINES KEY TO LOGS UNIFIED SOIL CLASSIFICATION SYSTEM CLEAN GRAVELS (Less than 5% fines) GRAVEL WITH FINES CLEAN SANDS (Less than 5% fines) GROUP SYMBOL GW GP GM GC SW SP SM SC SECONDARY DIVISIONS Well graded gravels, gravel-sand mixtures, little or no fines Poorly graded gravels, gravel-sand mixtures, little or no fines Silty gravels, gravel-sand-silt mixtures, non-plastic fines Clayey gravels, gravel-sand-clay mixtures, plastic fines Well graded sands, gravelly sands, little or no fines Poorly graded sands, gravelly sands, little or no fines Silty sands, sand-silt mixtures, non-plastic fines Clayey sands, sand-clay mixtures, plastic fines FINE GRAINED SOILS More than half of the material is smaller than the No. 200 sieve SILTS AND CLAYS Liquid limit less than 50 SILTS AND CLAYS Liquid limit greater than 50 ML CL OL MH CH Inorganic silts and very fine sands, silty or clayey fine sands or clayey silts with slight plasticity Inorganic clays of low to medium plasticity, gravelly clays, sandy clays, silty clays, lean clays Organic silts and organic silty clays of low plasticity Inorganic silts, micaceous or diatomacaceous fine sandy or silty soils, elastic silts Inorganic clays of high plasticity, fat clays OH Organic clays of medium to high plasticity, organic silts HIGHLY ORGANIC SOILS Pt Peat and other highly organic soils GRAIN SIZE LIMITS SILT AND CLAY FINE SAND MEDIUM COARSE FINE GRAVEL COARSE COBBLES BOULDERS No. 200 No. 40 No. 10 No. 4 3/4 in. 3 in. 12 in. US STANDARD SIEVE SIZE RELATIVE DENSITY CONSISTENCY MOISTURE CONDITION SAND AND GRAVEL BLOWS/FT* SILT AND CLAY BLOWS/FT* DRY VERY LOOSE LOOSE MEDIUM DENSE DENSE VERY DENSE OVER 50 VERY SOFT SOFT FIRM STIFF VERY STIFF HARD OVER 32 MOIST WET BEDROCK (GROUP SYMBOL) Brackets Denote Bedrock * Number of blows of 140 pound hammer falling 30 inches to drive a 2 inch O.D. (1 3/8 inch I.D.) split spoon (ASTM D-1586). CMAG ENGINEERING FIGURE A-2

38 LOG OF EXPLORATORY BORING Project No.: SC Boring: B-1 Project: O'Neill Ranch Well / Treatment Plant Location: See Boring Location Plan, Figure A-1 Santa Cruz County, California Elevation: 118+ Feet Date: June 13, 2012 Method of Drilling: Track Mounted Drill Rig, 4in. Solid Stem Logged By: ALG Auger, 140lb. Safety Hammer Depth (ft.) Soil Type Undisturbed Bulk 2" Ring Sample Terzaghi Split Spoon Sample 2.5" Ring Sample Description Static Water Table Bulk Sample Blows / Foot N 60 Dry Density (pcf) Moisture Content (%) Other Tests CL Very Dark Grayish Brown Sandy Lean CLAY. Very Stiff, Moist, Plastic. Sand - FG to MG SP- 5 SM Qcl: Dark Yellowish Brown Poorly Graded SAND w/ Silt and Trace Gravel. Dense, Moist, Non Plastic. Sand FG to MG. Gravel - up to 3/4", Subrounded SP- Olive Brown Poorly Graded SAND w/ Silt. Dense, Moist, Non Plastic. SM Sand - FG to MG SM Olive Brown Silty SAND w/ Gravel. Very Dense, Moist, Non Plastic. Sand - FG to CG. Gravel - up to 1.5", Subrounded Boring ft. Groundwater Not Encountered. Boring Backfilled With Cuttings CMAG ENGINEERING FIGURE A-3

39 LOG OF EXPLORATORY BORING Project No.: SC Boring: B-2 Project: O'Neill Ranch Well / Treatment Plant Location: See Boring Location Plan, Figure A-1 Santa Cruz County, California Elevation: 117+ Feet Date: June 13, 2012 Method of Drilling: Truck Mounted Drill Rig, 6in. Solid Stem Logged By: ALG Auger, 140lb. Safety Hammer Depth (ft.) Soil Type Undisturbed Bulk 2" Ring Sample Terzaghi Split Spoon Sample 2.5" Ring Sample Description Static Water Table Bulk Sample Blows / Foot N 60 Dry Density (pcf) Moisture Content (%) Other Tests CL Very Dark Grayish Brown Sandy Lean CLAY. Hard, Moist, Plastic E.I. = 55 SM Qcl: Light Yellowish Brown Silty SAND. Very Dense, Moist, Non Plastic R-Value = 17 Sand - FG Ф' = 39 5 c' = 0 psf SM Light Olive Brown Silty SAND. Medium Dense, Moist, Non Plastic Sand - FG to MG. 10 SP- Dark Yellowish Brown Poorly Graded SAND w/ Silt and Trace Gravel. SM Very Dense, Moist, Non Plastic. Sand - FG to CG Gravel - up to 1", Subrounded. 15 SM Grayish Brown Silty SAND w/ Gravel. Very Dense, Moist, Non Plastic. Sand - FG to CG. Gravel - up to 1.5", Subrounded Boring 16+ ft. Groundwater Not Encountered. Boring Backfilled With Cuttings CMAG ENGINEERING FIGURE A-4

40 LOG OF EXPLORATORY BORING Project No.: SC Boring: B-3 Project: O'Neill Ranch Well / Treatment Plant Location: See Boring Location Plan, Figure A-1 Santa Cruz County, California Elevation: 117+ Feet Date: June 13, 2012 Method of Drilling: Truck Mounted Drill Rig, 6in. Solid Stem Logged By: ALG Auger, 140lb. Safety Hammer Depth (ft.) Soil Type Undisturbed Bulk 2" Ring Sample Terzaghi Split Spoon Sample 2.5" Ring Sample Description Static Water Table Bulk Sample Blows / Foot N 60 Dry Density (pcf) Moisture Content (%) Other Tests CL Very Dark Grayish Brown Sandy Lean CLAY. Hard, Moist, Plastic SM Qcl: Yellowish Brown Silty SAND. Dense, Moist, Non Plastic. Sand - FG SM Olive Brown Silty SAND w/ Gravel. Very Dense, Moist, Non Plastic Sand - FG to CG. Gravel - up to 1", Subrounded. SP- Yellowish Brown Poorly Graded SAND w/ Silt and Gravel. 10 SM Very Dense, Moist, Non Plastic. Sand - FG to CG Gravel - up to 3/4", Subrounded. 15 Boring 10+ ft. Groundwater Not Encountered. Boring Backfilled With Cuttings CMAG ENGINEERING FIGURE A-5

41 LOG OF EXPLORATORY BORING Project No.: SC Boring: B-4 Project: O'Neill Ranch Well / Treatment Plant Location: See Boring Location Plan, Figure A-1 Santa Cruz County, California Elevation: 114+ Feet Date: June 13, 2012 Method of Drilling: Truck Mounted Drill Rig, 6in. Solid Stem Logged By: ALG Auger, 140lb. Safety Hammer Depth (ft.) Soil Type Undisturbed Bulk 2" Ring Sample Terzaghi Split Spoon Sample 2.5" Ring Sample Description Static Water Table Bulk Sample Blows / Foot N 60 Dry Density (pcf) Moisture Content (%) Other Tests CL Very Dark Grayish Brown Sandy Lean CLAY. Hard, Moist, Plastic. SM Qcl: Dark Yellowish Brown Silty SAND w/ Gravel. Dense, Moist, Non Plastic. Sand - FG to CG. Gravel - up to 1", Subangular to Subrounded Particle Size FC = 23.1% SM Yellowish Brown Silty SAND w/ Gravel. Very Dense, Moist, Non Plastic Particle Size 10 Sand - FG to CG. Gravel - up to 1", Subangluar. FC = 18.3% 15 SM Yellowish Brown Silty SAND w/ Gravel. Very Dense, Moist, Non Plastic Sand - FG to CG. Gravel - up to 1.5", Subangluar. 20 (SP- Tp: Olive Brown SANDSTONE. Very Dense, Moist Particle Size SM) Poorly Graded Sand w/ Silt. Weakly Cemented. Sand - FG to MG. FC = 5.9% Ф' = 33 c' = 420 psf 25 (SP) Olive Brown SANDSTONE. Very Dense, Moist Poorly Graded SAND. Weakly Cemented. Sand - FG to MG. 30 (SP) Material Consistent Particle Size FC = 1.8% 35 CMAG ENGINEERING FIGURE A-6.0

42 LOG OF EXPLORATORY BORING Project No.: SC Boring: B-4, Continued Project: O'Neill Ranch Well / Treatment Plant Location: See Boring Location Plan, Figure A-1 Santa Cruz County, California Elevation: 114+ Feet Date: June 13, 2012 Method of Drilling: Truck Mounted Drill Rig, 6in. Solid Stem Logged By: ALG Auger, 140lb. Safety Hammer Depth (ft.) Soil Type Undisturbed Bulk 2" Ring Sample Terzaghi Split Spoon Sample 2.5" Ring Sample Description Static Water Table Bulk Sample Blows / Foot N 60 Dry Density (pcf) Moisture Content (%) Other Tests (SP) Dark Gray and Dark Yellowish Brown SANDSTONE. Very Dense, Moist Poorly Graded SAND. Weakly Cemented. Sand - FG to MG. 40 (SP) Material Consistent Boring ft. Groundwater Not Encountered. Boring Backfilled With Cuttings CMAG ENGINEERING FIGURE A-6.1

43 Project No.: Project: Date: Logged By: Depth (ft.) Soil Type ALG Undisturbed Bulk SC O'Neill Ranch Well / Treatment Plant Santa Cruz County, California June 13, " Ring Sample Terzaghi Split Spoon Sample LOG OF EXPLORATORY BORING 2.5" Ring Sample Description Static Water Table Boring: Location: Elevation: Method of Drilling: Bulk Sample B-5 See Boring Location Plan, Figure A Feet Truck Mounted Drill Rig, 6in. Solid Stem Auger, 140lb. Safety Hammer Blows / Foot N 60 Dry Density (pcf) Moisture Content (%) Other Tests 5 CL Very Dark Grayish Brown Sandy Lean CLAY. Hard, Moist, Plastic. Sand - FG SM Qcl: Light Yellowish Brown Silty SAND. Dense, Moist, Non Plastic Sand - FG. SM Material Consistent Particle Size FC = 46.6% 10 SM Dark Yellowish Brown Silty SAND w/ Gravel. Very Dense, Moist, Non Plastic. Sand - FG to CG. Gravel - up to 1", Subangular. 15 SM Dark Yellowish Brown Silty SAND w/ Gravel. Very Dense, Moist, Non Plastic. Sand - FG to CG. Gravel - up to 1.5", Subangular. Coarse Gravels in Cuttings, up to 3". 20 SM Dark Yellowish Brown Silty SAND w/ Gravel. Very Dense, Moist, Non Plastic. Sand - FG to CG. Gravel - up to 1.5", Subangular (SP- Tp: Dark Gray and Dark Yellowish Brown SANDSTONE. Very Dense, SM) Moist. Poorly Graded Sand w/ Silt. Weakly Cemented. Sand - FG to MG Boring ft. Groundwater Not Encountered. Boring Backfilled With Cuttings. 35 CMAG ENGINEERING FIGURE A-7

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45 APPENDIX B LABORATORY TESTING PROGRAM Laboratory Testing Procedures Page B-1 Direct Shear Test Results Figures B-1 and B-2 Particle Size Distribution Test Results Figures B-3 through B-7 Expansion Index Test Results Table B-1 R-Value Test Results Table B-2

46 Geotechnical Investigation August 23, 2012 Santa Cruz County, California Page B-1 Classification LABORATORY TESTING PROCEDURES Soils were classified according to the Unified Soil Classification System in accordance with ASTM D 2487 and D Moisture content and dry density determinations were made for representative, relatively undisturbed samples in accordance with ASTM D Results of moisture-density determinations, together with classifications, are shown on the Boring Logs, Figures A-3 through A-7. Direct Shear Consolidated drained direct shear tests were performed in accordance with ASTM D 3080 on representative, relatively undisturbed samples of the on-site soils. To simulate possible adverse field conditions the samples were saturated prior to shearing. A saturating device was used which permitted the samples to absorb moisture while preventing volume change. The direct shear test results are presented on the Boring logs on Figures B-1 and B-2. Particle Size Distribution Particle size distribution tests were performed on representative samples of the underlying soils to determine the particle size distribution in accordance with ASTM D 422. The test results are presented on Figures B-3 through B-7. Expansion Index An expansion index test was performed on a representative remolded sample of the on-site soils in accordance with the ASTM D The test results are presented in Table B-1. R-Value A R-Value test was performed on a representative sample of the on-site soils in accordance with Caltrans California Test 301. The test results are presented in Table B-2.

47 Geotechnical Investigation August 23, 2012 Santa Cruz County, California Page B-2 Table B-1. Expansion Index Test Results Test Location Soil Type Expansion Index Expansion Potential 1-2 Feet CL 55 Medium Table B-2. R-Value Test Results Test Location Soil Type R-Value 2-3 Feet SM 17

48 BORING: DEPTH (ft): SOIL TYPE (USCS): B-2 COHESION FRICTION 3.0 (psf) ANGLE SM PEAK 0 39 FULLY SOFTENED MOISTURE: SATURATED TEST TYPE: CONSOLIDATED - DRAINED SHEAR STRESS (psf) NORMAL LOAD (psf) CMAG ENGINEERING DIRECT SHEAR TEST RESULTS O'Neill Ranch Well / Treatment Plant FIGURE B-1

49 BORING: DEPTH (ft): SOIL TYPE (USCS): B-4 COHESION FRICTION 20.0 (psf) ANGLE (SP-SM) PEAK FULLY SOFTENED MOISTURE: SATURATED TEST TYPE: CONSOLIDATED - DRAINED SHEAR STRESS (psf) NORMAL LOAD (psf) CMAG ENGINEERING DIRECT SHEAR TEST RESULTS O'Neill Ranch Well / Treatment Plant FIGURE B-2

50 BORING: B-4 PERCENT PERCENT DEPTH (ft): 3.0 PASSING No. 4 PASSING No. 200 SOIL TYPE (USCS): SM 83.5% 23.1% 100% 90% 80% 70% PERCENT PASSING 60% 50% 40% 30% 20% 10% 0% PARTICLE SIZE (mm) CMAG ENGINEERING PARTICLE SIZE DISTRIBUTION O'Neill Ranch Well / Treatment Plant FIGURE B-3

51 BORING: B-4 PERCENT PERCENT DEPTH (ft): 9.0 PASSING No. 4 PASSING No. 200 SOIL TYPE (USCS): SM 78.8% 18.3% 100% 90% 80% 70% PERCENT PASSING 60% 50% 40% 30% 20% 10% 0% PARTICLE SIZE (mm) CMAG ENGINEERING PARTICLE SIZE DISTRIBUTION O'Neill Ranch Well / Treatment Plant FIGURE B-4

52 BORING: B-4 PERCENT PERCENT DEPTH (ft): 20.0 PASSING No. 4 PASSING No. 200 SOIL TYPE (USCS): (SP-SM) 100.0% 5.9% 100% 90% 80% 70% PERCENT PASSING 60% 50% 40% 30% 20% 10% 0% PARTICLE SIZE (mm) CMAG ENGINEERING PARTICLE SIZE DISTRIBUTION O'Neill Ranch Well / Treatment Plant FIGURE B-5

53 BORING: B-4 PERCENT PERCENT DEPTH (ft): 30.0 PASSING No. 4 PASSING No. 200 SOIL TYPE (USCS): (SP) 100.0% 1.8% 100% 90% 80% 70% PERCENT PASSING 60% 50% 40% 30% 20% 10% 0% PARTICLE SIZE (mm) CMAG ENGINEERING PARTICLE SIZE DISTRIBUTION O'Neill Ranch Well / Treatment Plant FIGURE B-6

54 BORING: B-5 PERCENT PERCENT DEPTH (ft): 5.0 PASSING No. 4 PASSING No. 200 SOIL TYPE (USCS): SM 99.3% 46.6% 100% 90% 80% 70% PERCENT PASSING 60% 50% 40% 30% 20% 10% 0% PARTICLE SIZE (mm) CMAG ENGINEERING PARTICLE SIZE DISTRIBUTION O'Neill Ranch Well / Treatment Plant FIGURE B-7

55 APPENDIX C SLOPE STABILITY RESULTS Overall Slope Stability For Cross Section A-A Existing Configuration - Static Case Figure C-1 Existing Configuration - Pseudostatic Case Figure C-2

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