ZCR_Geotechnical_Investigation.pdf

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PREPARED FOR:

AARRAAMMAARRKK

FEBRUARY 2018

FILE: 2126

TABLE OF CONTENTS

i

1.0 INTRODUCTION

2.0 SITE DESCRIPTION

3.0 PROJECT DESCRIPTION

4.0 FIELD EXPLORATION

4.1 Test Pits

4.2 Dynamic Cone Penetrometer

4.3 Geophysical Measurements

5.0 LABORATORY TESTING

6.0 GEOLOGIC AND GENERAL SOIL PROFILE DESCRIPTIONS

6.1 General Soil Profile

6.2 Relative Soil Consistency/Density

6.3 Groundwater Conditions

7.0 SEISMIC AND GEOLOGIC HAZARDS

7.1 Seismicity

7.2 Faults

8.0 SEISMIC DESIGN PARAMETERS

9.0 DISCUSSION AND RECOMMENDATIONS

9.1 Construction and Grading Recommendations

9.1.1 Site Clearing and Preparation

9.1.2 Subgrade Preparation

9.1.3 Grading and Filling

9.1.4 Stabilization

9.1.4.1 Stabilizing Fill

9.1.5 Remedial Earthwork

9.1.6 Trenching and Confined Excavations

9.1.7 Excavatability

9.2 Foundations

9.2.1 Foundation Grade Soils Preparation

9.2.2 Isolated or Continuous Footings

9.2.3 Concrete Slabs

9.2.4 Lateral Resistance

9.2.5 Static Settlement

9.2.6 Moisture Vapor Retarder

9.3 Lateral Earth Pressure

9.5 Corrosion Potential

9.6 Site Drainage Considerations

10.0 LIMITATIONS

REFERENCES

TABLE OF CONTENTS

ii

TABLES

Table 1: Relative Soil Consistency-DCP Soundings Table 2 – Site Classification Definition Table 3 – Seismic Design Parameters Table 4 – Guideline Specifications For Imported Structural Fill Table 5 - Stabilizing Fill Geotextile Table 6 – Stabilizing Fill Gradation Specifications Table 7 – Maximum Allowable Temporary Slopes Table 6 – Foundation Design Parameters Table 7 – Lateral Earth Pressure Values

FIGURES

Figure 1: Vicinity Map Figure 2: Preliminary Site Layout (N.T.S) Figure 3: One-Dimensional Shear-Wave Velocity Profile (ft/s) Figure 4: NBMG Interactive Fault Map Excerpt Figure 5: Typical Removal/Replacement Detail

APPENDICES

Appendix A Plate A-1 – Field Exploration Location Map and Vicinity Map Plate A-2 – Test Pit Logs Plate A-3 – Soil Classification Chart Plate A-4 – DCP Soundings

Appendix B Plate B-1 – Grain Size Analysis Plate B-2 – Moisture Density Curve Plate B-3 – Corrosion Test Results

Appendix C USGS Design Maps Summary Report

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GEOTECHNICAL INVESTIGATION

ZEPHYR COVE TICKET SALES BUILDING

ZEPHYR COVE, SOUTH LAKE TAHOE, NEVADA

1.0 INTRODUCTION

Presented herein are the results of Construction Materials Engineers Inc. (CME) geotechnical exploration, laboratory testing, and associated geotechnical design recommendations for the Zephyr Cove Ticket Sales Building to be located on U.S. Forest Service at 760 US Highway 50, in Zephyr Cove, Nevada. The geotechnical recommendations contained herein are based on surface and subsurface conditions encountered during our field exploration, and on details of the proposed project as described in this report.

The objectives of this study were:

1. Investigate general soil and groundwater conditions pertaining to design and construction of the proposed project; and

2. Provide geotechnical recommendations for design and construction of the project, based on the results of our field and laboratory studies.

Our geotechnical study included subsurface field exploration, geophysical studies, laboratory testing, and engineering analysis to provide recommendations for project design.

The area covered by this report is shown on Plate A-1 (Field Exploration Location Map) in Appendix A.

Results of our field exploration and testing programs form the basis for all conclusions and recommendations.

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2.0 SITE DESCRIPTION

The proposed ticket booth structure will be located on U.S. Forest Service land near the Miss Dixie launch area; at 760 US-50, Zephyr Cove, Nevada 89488. The project site is located entirely in S10, T13N, R18E (M.D.M), in the northwestern portion of Assessor Parcel Number 1318-03-000-002, as shown in Figure 1 (Vicinity Map).

Figure 1: Vicinity Map

(Reference Base Maps: Motor Vehicle Use Map-Lake Tahoe Basin (https://www.fs.usda.gov/Internet/FSE_DOCUMENTS/fsm9_046264.pdf) and

Douglas County Parcel Maps, http://www.douglascountynv.gov/615/Parcel-Maps, accessed January 2018).

The project site is located within the limits of the Zephyr Cove Resort on the southeast side of Lake Tahoe.

The proposed ticket booth structure will be located north of the existing Sunset Bar and Grill. The subject site gently slopes in a west-northwest direction towards Lake Tahoe. Existing development near the building pad includes subsurface utilities, gas tank and gas pumps directly east-southeast, and asphalt concrete pavement near the southwest building corner. The proposed ticket booth is bound to the south by an existing driveway/access road for the pier, a gas tank to the east, existing A-frame booth, beach to the west, and paved access road to the north.

GENERAL

PROJECT

VICINITY

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Photograph 1: Taken looking South at the Proposed Ticket Booth Building Pad Location

Vegetation at the site is sparse with a single large pine tree located on the southern edge of the building pad. The proposed ticket booth building will likely require the removal of the existing mature pine tree.

GENERAL LIMITS OF

PROPOSED BUILDING

FOOTPRINT

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3.0 PROJECT DESCRIPTION

The project is currently in the early planning phases and civil/grading plans are not available. Based on information provided by Michael Alexander, PE, with the U.S. Forest Service, it is anticipated that the proposed ticket booth will be an approximate 1,600 square foot, single story timber framed structure. The building will be supported using slab on grade with continuous spread footings. The building footprint is located approximately 140 feet east of Lake Tahoe.

Based on the site topography, it is anticipated that cuts and fills on the order of 2 feet or less will be required to create a level building pad. The preliminary site layout is included as Figure 2 (Preliminary Site Plan).

Figure 2: Preliminary Site Layout (N.T.S) (Reference: Site Plan, Monarch Architecture, undated; electronically received December 2017)

Structural loads were not available at the time this report was prepared, based on the anticipated structure type, loads are anticipated to be light. Foundations loads on the order of 2 to 3 kips per linear foot for continuous spread footings and up to 10 kips at isolated spread footings.

N

PROPOSED

BUILDING

LAYOUT

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4.0 FIELD EXPLORATION

The subsurface field exploration included test pit excavations, geophysical measurements, and dynamic cone penetrometer testing. The subsurface exploration methods used are described in Sections 4.1 (Test Pits), 4.2 (Dynamic Cone Penetrometer), and 4.3 (Geophysical Measurements).

4.1 Test Pits

The subsurface field exploration, completed on December 13, 2017, consisted of excavating two test pits.

The test pits were excavated using a Case 580M Plus Series 2 rubber-tired backhoe equipped with a 18-inch bucket. The test pits were located in the field by visual sighting and/or measuring from existing features at the site. The locations included in this report should be considered accurate only to the degree implied by the methods used. The approximate test pit locations are presented on Plate A-1.

Following completion of the test pit excavations, test pits were backfilled using the equipment at hand. Test pit back-fill was loosely placed and not compacted to the standards typically required for properly placed engineered fill1.

Soils encountered within the test pit excavation were visually classified in general accordance with ASTM D2488 (Description and Identification of Soils). Bulk samples of representative soil strata were collected, placed in sealed plastic bags, and returned to our laboratory. Upon completion of laboratory testing, additional soil classifications and verification of the field classifications were subsequently performed in accordance with the Unified Soil Classification System (USCS), as presented in ASTM D2487. Test pit logs are included as Plate A-2. A description of the USCS is presented on Plate A-3.

4.2 Dynamic Cone Penetrometer

To supplement the test pit excavations and limit ground disturbance beneath the proposed structure foot print, Dynamic Cone Penetrometer (DCP) soundings were performed. A total of five (5) DCP soundings were completed across the structure footprint. DCPs were advanced to depths ranging from 9 to 10 feet bgs.

The DCP probe is a portable, manually operated device used to continually measure the consistency and relative strength of loose to dense soils.

Blow counts are recorded in the field at 10 cm intervals and converted to Standard Penetration Test (SPT) N-value using the Wildcat Dynamic Cone Log software. The N-value is a measure of the standard penetration resistance of the soil and provides an indication of the relative density of the underlying soil strata. DCP logs are included as Plate A-4 (Log of DCP). It should be noted that the upper 1-foot of the soils profile was frozen at DCP locations DCP-1, DCP-2, DCP-3, and DCP-5. The upper 1-foot of blow count (N’) information collected was neglected for our subsequent analysis.

1 Warning: Structures and or slabs constructed over loosely placed back-fill may experience significant settlement and/or differential settlement. Removal and recompaction of back-fill may be required prior to construction over these areas.

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4.3 Geophysical Measurements

Geophysical field measurements using the Refraction Microtremor (ReMi) were performed in general accordance with the method described by Louie (2001). The ReMi method provides an effective and efficient means to obtain basic subsurface profile information on an essentially continuous basis across the explored location. Shear wave velocity measurements were completed with the line trending from the southeast corner to the northwest, bisecting the proposed location of the ticket booth building.

The DAQlink III 24-bit acquisition system (Seismic Source/Optim) utilizing a multichannel geophone cable with twelve geophones, placed at an approximate spacing of 10 feet was used to obtain surface wave data.

This was then analyzed to obtain an S-wave vertical profile. Vertical geophones with resonant frequencies of 10 Hz measure surface wave energy from broad band ambient site noise across the geophone array (i.e.

ReMi setup location) for multiple 30-second iterations.

SeisOpt® ReMiTM Version 4.1 software (© Optim, Inc.) was used to analyze data files collected in the field. Dispersion curve picks can either be interactively modeled using trial-and-error adjustments or using an automatic inversion code to obtain a one-dimensional shear-wave (S-wave) velocity versus depth profiles. The shear-wave profile can further be calibrated and fine-tuned integrating existing logs or blow counts information.

The resulting S-wave velocity profiles were evaluated to assist in determining the soil Site Classification (refer to Section 8.0 - Seismic Design Parameters) in accordance with 2012 IBC. Results are included as Figure 3 (One-Dimensional Shear Wave Velocity Profile).

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Figure 3: One-Dimensional Shear-Wave Velocity Profile (ft/s)

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5.0 LABORATORY TESTING

Soils testing performed in CME’s laboratory was conducted in general accordance with the standards and methodologies described in Volume 4.08 of the ASTM Standards.

Significant soil types were selected and analyzed to determine index properties and engineering properties.

The following laboratory tests were completed as part of this investigation:

Insitu moisture content (ASTM D2216) (Appendix A);

Plasticity Index and Liquid Limit (ASTM D4318) (Appendix A/B);

Grain size distribution (ASTM D6913) (Appendix B);

Moisture Density Curve (ASTM D1557) (Appendix B); and Corrosion testing (soluble sulfates, resistivity, and pH) was completed by an outside laboratory

(Appendix B).

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6.0 GEOLOGIC AND GENERAL SOIL PROFILE DESCRIPTIONS

Based on a review of the Glenbrook Quadrangle Geologic Map (Grose, T.L.T., 1985), the project site is underlain by beach sand with carbonaceous alluvium mapped immediately east. The beach sand is described as arkosic2, fine to very coarse grained with a thickness of less than 25 meters. The carbonaceous alluvium is described as clayey to sandy, dark gray to black, variously organic that occurs in marshy back-beach alluvial tracts.

The Geologic Map of the lake Tahoe Basin California and Nevada (Saucedo, 2005), maps the site as being underlain by Holocene aged beach sand and flood plain deposits.

6.1 General Soil Profile

In general, the soils profile encountered within the test pit excavations appear to be consistent with the mapped geologic conditions. The uppermost soils horizon consists of poorly graded sand (SP) to poorly graded sand with silt (SP-SM) approximately 1 to 3 feet thick. Test Pit TP-1 was terminated at a depth of about 3 feet due to water line conflict.

Soils encountered within Test Pit TP-2, below the silty sand (SM) to the depth of exploration. Silty sand encountered from a depth of about 2 feet to 4 feet consisted of dark grey to black borderline soil classification with nearly 47 percent passing the #200 sieve. This organic rich silty sand was encountered with a moisture content of about 63 percent, plasticity index of 10, and a liquid limit of 53.

At a depth of 4 feet to the termination depth of the excavation, the silty sand (SM) soils became substantially more granular with about 12 percent passing #200 sieve.

Based on a review the well log (Log ID ZC-MW-7, by Arcadis, dated January 9, 2012), soils encountered were similar to those encountered within the test pit excavations. As indicated on the log, at a depth of about 8 ½ feet soils encountered within the well borehole consisted of a well graded sand (SW) to the termination depth of about 23 feet.

6.2 Relative Soil Consistency/Density

DCP soundings were completed to determine the relative soil consistence across the building pad. In general soils were encountered in a loose to medium dense condition. Low blow counts were consistently encountered within DCP-1, located adjacent to and existing utility trench.

Based on the soils types encountered a summary of the relative soil consistence per DCP location is included as Table 1 (Relative Soil Consistency-DCP Soundings).

2 A sand rich in feldspar generally formed from weathering of feldspar-rich igneous or metamorphic rocks (usually granite) in an environment where the feldspar does not undergo significant chemical weathering and decomposition.

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Table 1: Relative Soil Consistency-DCP Soundings

DCP ID General Location Depth (ft) Tested Consistency

Based on Cone Resistance (1, 2)

DCP-1 NW Building Corner

1’ to 9’

9’ to 10’

Loose (2<N’<9)

Medium Dense (20<N’<25+)

DCP-2 SW Building Corner

1’ to 2’

2’ to 4’

5’ to 9’

(13<N’<24)

Loose/Medium Stiff

(5<N’<11)

(11<N’<25+)

DCP-3 SE Building Corner 1’ to 10’ Medium Dense

(13< N’<25+)

DCP-4 NE Building Corner

1’ to 2’

2’ to 5’

5’ to 6’

6’ to 10’

Loose (N’<6)

(13<N’<18)

Loose/Soft (4<N’<7)

Medium Dense to

Dense (12<N’<25+)

DCP-5 Near Building Center

1’ to 4’

4’ to 7’

7’ to 10’

(15<N’<20)

Loose/Soft (2<N’<9)

(15<N’<25+)

1. Relative Soil consistency varies based on soil type (i.e. cohesive soils (clays), and non-cohesive soil types (sands, granular material). Typical descriptions of the SPT N-Value and Soils Consistency is presented on Plate A-3

2. N’ corresponds to correlated SPT N-value3 based on DCP cone resistance.

3 Standard Penetration Test, SPT, is defined as a thick-walled split-spoon sampler driven by a standard 140-pound drive hammer with a 30-inch stroke. The number of blows to drive the sampler the final 12 inches of an 18-inch penetration into undisturbed soil is an indication of the density and consistency of the material (Standard Penetration Test (SPT) - ASTM D1586), commonly termed "standard penetration resistance" or the "N-value"

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6.3 Groundwater Conditions

Seepage was observed during our field exploration at depth of about 3 to 4 feet bgs. Based on existing well logs provided by the US Forest Service (Well Log ZC-MW-7), a stabilized water level was recorded at a depth of about 3 ½ feet bgs (on September 9, 2011). Groundwater levels are expected to closely emulate the stabilized surface elevation of Lake Tahoe based on the proximity of the lake to the project site and the predominately granular nature of the onsite soils. Dewatering may be required during construction and will be dependent on the season of construction and depth of excavation. Sump pumps with multiple discharge points may be used, but the appropriate most effective method of dewatering will need to be determined by the contractor during construction.

7.0 SEISMIC AND GEOLOGIC HAZARDS

7.1 Seismicity

The Western United States is a region of moderate to intense seismicity related movement of the crustal masses (plate tectonics). The most active regions outside of Alaska are along the San Andreas Fault Zone of western California and the Wasatch Front in Salt Lake City.

Figure 4: Overview Map Showing the Great Basin

(N.T.S)

The Wasatch Front in Salt Lake City, Utah, forms the eastern boundary of the Basin and Range physiographic province, and the eastern form of the Sierra Nevada Mountains, which is the western margin of the province. The project site is located in a seismically active zone within the western extreme of the Basin and Range.

GENERAL

PROJECT

VICINITY

N

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7.2 Faults

To determine the location of mapped earthquake faulting trending through or near the project site, a review of the following published information was completed:

1) USGS Website: Earthquake Hazards Program Quaternary Faults in Google Earth;

2) The USGS Interactive Fault Map (http://earthquake.usgs.gov/hazards/qfaults/map/); and

3) Quaternary Faults in Nevada, included as Figure 5, (dePolo, 2008).

The project site is located between two fault traces, both associated with the East Tahoe Fault. The East Tahoe Fault generally trends north-south along the eastern edge of Lake Tahoe. The project is located approximately ½-mile west of one fault and 1-mile east of another fault. Both of these faults are classified as Quaternary Active. The nearest mapped Holocene aged (less than 10,000 years) fault is located on the western edge of Lake Tahoe, about 7 ½ miles west. This fault is named the West Tahoe Fault and is associated with the West Tahoe-Dollar Point Fault Zone.

Figure 5: NBMG Interactive Fault Map Excerpt (https://gisweb.unr.edu/QuaternaryFaults/, accessed February 2018)

Quaternary earthquake fault evaluation criterion has been formulated by a professional committee for the State of Nevada Seismic Safety Council, 2006, which defines Holocene Active Faults as those with evidence of displacement within the past 10,000 years (Holocene time). Those faults with evidence of displacement during Pleistocene time (10,000 to 1,600,000 years before present) are classified as either late Quaternary Active Fault (10,000 to 130,000 years) or Quaternary Active Fault (> 130,000 years). Both of the latter fault designations are considered to have a decreased potential for activity compared to the Holocene Active Fault. An inactive fault is considered to be a fault that does not comply with these age groups. The faults located near the project site (approximately ½-mile east and west associated with the

GENERAL

PROJECT

LOCATION

EAST TAHOE

FAULT (<1.8 MM

YRS)

WEST TAHOE -

DOLLAR POINT

FAULT

(<15 KA YRS)

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East Tahoe Fault) are classified as Quaternary Active Faults. Building setbacks for this fault age are not required.

7.3 Liquefaction

Liquefaction is nearly a complete loss of soil shear strength that can occur during an earthquake, as cyclic shear stresses generate excessive pore water pressure between the soil grains. The higher the ground acceleration caused by a seismic event or the longer the duration of shaking, the more likely liquefaction will occur.

The soil types most susceptible to liquefaction are loose to medium dense cohesionless sands, soft to stiff non-plastic to low plastic silts, or any combination of silt-sand mixtures lying below the groundwater table.

Liquefaction is generally limited to depths of 50 feet or less below the existing ground surface.

Shallow groundwater (encountered at a depth of about 4 feet bgs within nearby well) and the presence of loose sands within the upper profile indicate site soils are susceptible to liquefaction and secondary liquefaction hazards. Based on a review of the shear wave velocity profile, the risk for liquefaction is likely limited to the upper 10 to 15 feet of the soil profile where velocities are less than 500 feet per second. At a depth of about 20 feet the soil profile appears to transition to a higher velocity material consistent with bedrock with shear wave velocities on the order of 4,000 feet per second.

The extents of secondary hazards related to liquefaction settlement is unknown without performing a liquefaction investigation, including performing at least one boring to about 40 feet bgs, index testing of soil samples, and engineering analysis. Based on the proposed structure type (single story) and low seasonal occupation capacity of the structure, liquefaction mitigation is not required. Additionally, due to the exorbitant costs, it is likely mitigation of liquefiable soils will not be considered for project design.

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8.0 SEISMIC DESIGN PARAMETERS

Seismic design parameters are based on site-specific estimates of spectral response ground acceleration as designated in the 2012 IBC. The benefit of this approach is that a response spectrum can be developed from this data and based on the period of the structure, a spectral acceleration for that structure can be determined. These values are based on two criteria:

1) Site classification; and

2) Site location (latitude and longitude).

Site classification is based on the substrata soil profile type, as presented in Table 2 (Site Classification Definition).

Table 2 – Site Classification Definition

Site Classification Soil Profile Type Description

A Hard Rock B Rock C Very Dense Soil and Soft Rock D Stiff Soil Profile E Soft Soil Profile F Soil Type Requiring Site-Specific Evaluation

The soil/bedrock profile classification is based on two criteria: density (based on SPT blow count data) or hardness (based on shear wave velocity). These two criteria have to be determined to a depth of 100 feet below the ground surface.

Shear wave (S-wave) velocity measurements using the Refraction Microtremor (ReMi) were completed as described in Section 4.3 (Geophysical Measurements). The resulting S-wave velocity profile was evaluated to determine the soil Site Class in accordance with Section 1613.3.2 of the 2012 IBC.

The weighted average of the shear-wave velocity to a depth of 100 feet below existing grade was 1,451 feet per section, however, due to the presence of the loose sands within the upper 10 feet of the onsite soil profile (shear wave velocities <500 ft/s) a Site Class D is recommended for project design.

Spectral response acceleration values (Ss & S1) are based on structures underlain by bedrock with a site classification of B. Acceleration values may amplify or attenuate depending on the subsurface geologic conditions. Therefore, the building code provides correction factors to modify the acceleration values depending on the subsurface geologic conditions. These correction factors (Fa & Fv) are used if the site is located overlying subsurface geologic conditions with a site classification other than B. Spectral response acceleration values were determined from the USGS website: USGS Seismic Design Maps (Refer to Appendix C). Table 3 (Seismic Design Parameters) provides a summary of seismic design parameters.

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Table 3 – Seismic Design Parameters

PARAMETER DESCRIPTION PARAMETER

Approximate Latitude of Site 39.00712°N

Approximate Longitude of Site 119.94835°W

Peak Ground Acceleration-MCER PGAM (ASCE 7-10 Standard)

0.593 g

Spectral Response Acceleration at Short period (0.2 sec.) Ss (for Site Class B)

1.616 g

Spectral Response Acceleration at 1-second Period, S1 (for Site Class B)

0.554 g

Site Class Selected for this Site D

Site Coefficient Fa, decimal 1.000

Site Coefficient Fv, decimal 1.500

Design Spectral Response Acceleration at Short period, SDS (Adjusted to Site Class D, SDs= 2/3 SMs)

1.077 g

Design Spectral Response Acceleration at 1-second Period, SD1 (Adjusted to Site Class D, SD1=2/3 SM1)

0.554 g

1) MCER PGAM- Maximum credible earthquake geometric mean peak ground acceleration adjusted to Site Class D.

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9.0 DISCUSSION AND RECOMMENDATIONS

Based on the results of our subsurface exploration, site observations and analysis, it is our opinion that the site may be developed as planned4 provided the recommendations in this report are adhered to.

The following definitions shall apply for this project:

Structural areas referred to in this report include all areas that will be used for the support of foundations, concrete slabs, retaining walls, flat work, and asphalt pavements;

All compaction requirements presented in this report are relative to ASTM D15575;

Fine-grained soil is defined as a soil with more than 40 percent by weight passing the number 200 sieve and a plasticity index less than 15.

Clay soil is defined as a soil with more than 20 percent by weight passing the number 200 sieve and a plasticity index more than or equal to 15.

Granular soil is defined as a soil not meeting the requirement for a fine-grained or clay soil and having a particle size of 4-inches or less.

Subgrade is defined as the elevation directly below the aggregate base layer for both concrete slabs-on-grade and pavements.

The recommendations provided herein, and particularly under Site Preparation, Grading and Filling, Foundation Design, Site Drainage and Construction Observation and Testing are intended to reduce risks of structural distress related to consolidation or expansion of native soils and/or structural fills. These recommendations, along with proper design and construction of the planned structure(s) and associated improvements, work together as a system to improve overall performance. If any aspect of this system is ignored or poorly implemented, the performance of the project will suffer. Sufficient construction observation and testing should be performed to document that the recommendations presented in this report are followed.

Three primary construction concerns were identified during this exploration:

Groundwater was not encountered within the test pit excavations. The maximum depth of exploration occurred at an approximate elevation of about 6233.5 feet. Groundwater was encountered within well/boring ID ZC-MW-7 (39.0073496o N, -119.9483719oE) at a depth of about 3 ½ feet. Based on the casing elevation shown on the well log, groundwater may be encountered at an elevation of about 6,232.8 feet. The coordinates presented on the well log, indicate the boring was completed approximately 90 feet north of the future structure.

Based on the DCP soundings performed, the presence of loose sandy soils and soft to stiff fine-grained soils were encountered to depths ranging from 2 to about 4 feet on average across the building pad. Soil consistency encountered in DCP-1 was in a very loose to loose condition to a

4 Any evaluation of the site for the presence of surface or subsurface hazardous substances is beyond the scope of this study. When suspected hazardous substances are encountered during routine geotechnical investigations, they are noted in the exploration logs and reported to the client. No such substances were identified during our exploration.

5 Relative compaction refers to the ratio percentage of the in-place density of a soil divided by the same soil’s maximum dry density as determined by the ASTM D1557 laboratory test procedure. Optimum moisture content is the corresponding moisture content of the same soil at it maximum dry density.

Zephyr Cove Ticket Booth Geo Report 2-28-18.docx 17 depth of about 9 feet. DCP-1 is located near the northwest quadrant the proposed structure. Based on a review of the existing site plan (Refer to Plate A-1, Exploration Location Map), DCP-1 may have been completed at the edge of an existing utility trench, and blow counts may not be representative of the onsite native soil consistence.

Fine-grained soils (as defined in Section 9.0 of this report) were encountered at a depth of about 2 to 4 feet within test pit TP-2. This soil classifies as a silty sand (SM) with a fines content of about 47 percent and a moisture content of nearly 64 percent. This soil layer should be removed and replaced with properly densified structural fill prior to placement of structure foundations. The removal shall extend to a depth of at least 2 feet below the bottom of footing elevation and extend laterally a distance of three feet beyond the exterior perimeter of the proposed structure. The removal should encompass the entire structure footprint. The removed organic rich soils should be stockpiled onsite for reuse as topsoil in landscape areas if permitted by TRPA or local governing standards.

Based on the soil conditions encountered within test pit TP-2, this overexcavation may extend to a depth of about 6,232 feet if existing grades are to be maintained. Based on the nearby well log, and seepage observed in the field, this zone may be saturated or below the groundwater table.

Saturated soils will likely be unstable. Recommendations for stabilizing fill are included as Section

9.1 (Construction and Grading Recommendations).

9.1 Construction and Grading Recommendations

9.1.1 Site Clearing and Preparation

All vegetation and topsoil should be stripped and grubbed from structural areas and removed from the site prior to initiating fill placement or construction activities. Stripped and grubbed material should not be incorporated into structural fill. Based on the soil profile encountered, it is recommended that stripping and grubbing be required to a depth of about 3-inches. There is a large pine tree currently located within the building footprint. The entire root bulb should be removed as part of this tree removal. Large roots (greater than 2 inches in diameter) radiating from the tree bulb area, located within 2-feet of the final subgrade or foundation grade elevation, should be completely removed. Resulting excavations should be backfilled with structural fill].

Subgrade soils should be prepared in accordance with Section 9.2.1 (Foundation Grade Soils Preparation).

9.1.2 Subgrade Preparation

For areas subjected to structural loading or areas to receive structural fill site preparation recommendations are as follows:

Prior to placement of structural fill subgrade soils shall be scarified, moisture conditioned and densified to at least 90 percent (ASTM D1557). Where stabilization is required, subgrade soils shall not be densified. Unstable soils, where encountered, should be removed and replaced with either structural fill or stabilizing fill. To determine potential unstable soil areas, subgrade should be proof-rolled with heavy rubber-tired construction equipment such as a fully loaded water truck. Unstable areas, where encountered, should be removed and replaced with structural and/or stabilizing fill. The depth of soil removal will be determined during construction, but is anticipated to be at least 18 inches.

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Granular soils should be scarified to a minimum depth of 8 inches and moisture conditioned prior to densification. It is recommended that these soils have moisture contents of plus or minus 3 percent of optimum moisture (ASTM D1557) prior to densification. Moisture contents above 3 percent of optimum moisture will be acceptable if the soil horizon maintains its stability when subjected to construction equipment loads and density can be achieved in subsequent structural fill lifts.

Granular soils are not considered cohesive and the particles generally require shaking or vibratory action (i.e. smooth drum roller) for densification.

Clay soils (if encountered) should be scarified to a minimum depth of 12 inches, and moisture conditioned to 2 to 4 percent over optimum (ASTM D1557), prior to densification. It is mandatory that this moisture content be maintained by periodic surface wetting, or other methods, until the surface is covered by at least one lift of fill. Clay soil is considered cohesive and particles are best densified using high impact ram or sheepsfoot roller compactors.

Scarification and moisture conditioning including uniform mixing of site soils to achieve recommended soil moisture contents may be required. It is recommended that the moisture content of the in-situ soils be determined during construction to evaluate if moisture conditioning is required. After the densification process, a firm, stable surface should be produced.

Unstable soils, where encountered, should be removed and replaced with either structural fill or stabilizing fill. To determine potential unstable soil areas, subgrade should be proof-rolled with heavy rubber-tired construction equipment such as a fully loaded water truck. Unstable areas, where encountered, should be removed and replaced with structural and/or stabilizing fill. The depth of soil removal will be determined during construction, but is anticipated to be 18 inches or less.

9.1.3 Grading and Filling

Structural fill is defined as supporting soil placed below foundations, concrete slabs-on-grade, pavements, or any structural element that derives support from the underlying sub-soils.

Structural fill free of debris, vegetation, and organics shall meet the requirements for a granular soil or if imported shall meet the requirements given in Table 4 (Guideline Specifications for Imported Structural Fill).

In general, near surface onsite soils encountered appear to meet the requirements for granular soil and may be placed in structural areas. Fine-grained soils encountered within TP-2 at a depth of about 2 to 4 feet do not meet the requirements of a granular soil and should not be reused as structural fill. If required, imported structural fill free of debris, vegetation, and organics shall meet the requirements given in Table 4 (Guideline Specifications for Imported Structural Fill).

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Table 4 – Guideline Specifications for Imported Structural Fill

Sieve Size Percent Passing by Weight

4 inches 100 ¾ inch 70 - 100 No. 40 20 - 65 No. 200 5 - 30

Maximum Liquid Limit Maximum Plastic Index

30 10

Structural fill should be uniformly moisture conditioned within three percent of optimum moisture content, placed in layers of 8 inches or less in loose thickness, and densified to at least 90 percent relative compaction. Moisture contents greater than 3 percent of optimum moisture are acceptable if the soil lift is stable and required relative compaction can be attained in the soil lift and succeeding lifts.

No fill material should be placed, spread or rolled while it is frozen, thawing, or during unfavorable weather conditions.

9.1.4 Stabilization

Stabilization may be required where densification of the subgrade soils is not possible due to instabilities (i.e. pumping) during construction loading and densification efforts.

Stabilization consists of removing unstable or "pumping" soils and replacing them with a stabilizing fill overlying a geotextile.

The actual depth of subgrade soil removal shall be determined during construction.

However, unless a firmer surface is encountered at a shallower depth, the recommended minimum thickness of the stabilizing fill shall be 18-inches.

A high-performance geotextile shall be placed directly below the stabilizing fill to provide separation and stabilization. The geotextile should be woven and meet or exceed the minimum properties presented in Table 5 (Stabilizing Fill Geotextile).

Table 5 - Stabilizing Fill Geotextile

Mechanical Properties Minimum Average Roll Value (MARV)

MD (#/ft) CD (#/ft)

Tensile Strength at ultimate

(ASTM D 4595)

4800 4800

Tensile Strength at 5% strain

(ASTM D 4595)

2400 2700

Minimum permittivity (ASTM D 4491) 0.10 sec -1

Apparent Opening Size (AOS) 0.60 mm maximum

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Products such as a Terra Tex HPG-57, or approved equal can be utilized for this project.

Stabilizing fill (refer to Table 6 – Stabilizing Fill Gradation Specifications) with a minimum densified thickness of 12 inches shall be placed over the geotextile. Additional thicknesses may be required to ensure stabilization.

Prior to placement of the geotextile, the ground surface should be smooth without sharp particles or abrupt edges. The geotextile should be laid in accordance with the manufacturer’s recommendation with a minimum joint overlap of 18 inches. Construction equipment is prohibited from traveling directly over the geotextile. It is recommended that the initial lift of stabilizing fill be placed from outside the excavation or should be pushed ahead of the construction equipment during placement over the geotextile. Construction equipment should be light weight such as a tired backhoe.

The initial lift of stabilizing fill shall have a minimum loose lift thickness of 16 inches.

Subsequent lifts should be placed in maximum 12-inch lifts. It is recommended that prior to densification, the stabilizing fill be uniformly moisture conditioned to plus or minus 2 percent of optimum moisture. Higher moisture contents are acceptable if the soil lift is stable and required relative compaction can be attained in the soil lift and succeeding soil lifts. Stabilizing fill material should meet the requirements of Table 6 (Stabilizing Fill Gradation Specifications).

A test section is recommended to determine the required thickness of stabilizing fill.

Stabilization is always a trial and error procedure with requirements and effectiveness varying within the same project. Additionally, the contractor should avoid excessive densification efforts or construction equipment travel on subgrade soils that could cause instability in otherwise stable subgrade. It will be the contractor’s responsibility to limit/prevent damage to otherwise firm site soils.

9.1.4.1 Stabilizing Fill

Stabilizing fill material should be free of vegetation, organic matter, debris, and other deleterious material and meet the requirements of Table 6 (Stabilizing Fill Gradation Specifications).

Table 6 – Stabilizing Fill Gradation Specifications

Sieve Size Percent by Dry Weight Passing

6 Inch 100 ¾ Inch 70 - 100 No. 4 20 - 60

No. 200 0 - 8

Maximum Liquid Limit Maximum Plastic Index

35 5

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9.1.5 Remedial Earthwork

Remedial earthwork of the loose to soft soils, encountered from a depth about 1 to 4 feet bgs below the structure footprint will be required. These loose/soft soils shall be completely removed and replaced with densified structural fill meeting the requirements of Section

9.1.3 (Grading and Filling). The removal should encompass the entire foot-print and extend a minimum lateral distance of 3 feet beyond the outside edge of the structural element refer to Figure 4 (Typical Removal/Replacement Detail). Structural fill for remedial earthwork below the proposed Ticket Booth shall be densified to at least 93 percent relative compaction (ASTM D1557).

Figure 6: Typical Removal/Replacement Detail

In general, the loose/soft soils encountered from a depth of about 2 to 4 feet do not appear to meet the requirements for a granular soil or structural fill. These soils do appear to be rich in organic material and should not be reused below the structure footprint.

Care should be taken during grading operations not to mix this lower organic rich zone with the upper-most soils profile (0 to 2 feet bgs), as these soils appear to meet the requirements of a granular fill and can be reused in structural areas.

Structural fill placement should be completed in accordance with the recommendations presented in Sections 9.3 (Grading and Filling) of this report. It is recommended that a representative from CME be present to complete full-time observations and density testing during removal and placement.

9.1.6 Trenching and Confined Excavations

All excavations regardless of depth should be evaluated to check the stability prior to occupation by construction personnel. Shoring or sloping of trench walls may be required to protect construction personnel and provide temporary stability.

93%

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In areas where temporary confined excavations may be unstable, trench boxes may be used to provide safe ingress and egress for construction personnel.

Excavations should comply with current OSHA safety requirements (Federal Register 29 CFR, Part 1926). Soils or bedrock are classified as Type A, B or C, which require different temporary excavation cut slope gradients. Maximum allowable slopes for excavations less than 20 feet deep are presented in Table 7 (Maximum Allowable Temporary Slopes). The Contractor should expect Type C soils. Soil conditions should be verified during construction to assess required cut slope gradients.

Table 7 – Maximum Allowable Temporary Slopes

Soil or Rock Type Maximum Allowable Slopes1 For Deep Excavations Less Than 20 Feet Deep2

Stable Rock Type A3 Type B Type C

Vertical 3H:4V 1H:1V 3H:2V

(90 degrees) (53 degrees) (45 degrees) (34 degrees)

NOTES:

1. Numbers shown in parentheses next to maximum allowable slopes are angles expressed in degrees from the horizontal. Angles have been rounded off.

2. Sloping or benching for excavations greater than 20 feet deep shall be designed by a registered professional engineer.

3. A short-term (open 24 hours or less) maximum allowable slope of 1H:2V (63 degrees) is allowed in excavations in Type A soil that are 12 feet or less in depth. Short-term maximum allowable slopes for excavations greater than 12 feet in depth shall be 3H:4V (53 degrees).

Trench excavations should be protected from surface water/runoff. Temporary drainage swales should be excavated to divert surface flows into a collection area away from the open excavation. If warranted, dewatering of pipe trench excavations can be accomplished by use of a temporary dewatering system.

If subsurface water conditions differ from those encountered during our subsurface exploration, the geotechnical engineer should be notified immediately to determine if alternative dewatering recommendations are warranted.

9.1.7 Excavatability

Based on the conditions encountered, excavations may be completed using conventional excavation equipment such as a track mounted excavator or rubber-tired backhoe.

9.2 Foundations

The project is in the preliminary phases, and structural loads were not available at the time this report was prepared. For the purposes of this report, it is assumed that structural loads will be light on the order of 2 to 4 kips per linear foot for continuous spread footings and up to 10 kips for isolated column footings. It is anticipated the proposed structure will be supported on continuous spread foundations with slab-on-grade construction. Recommendations for foundation grade soils preparation and foundation design are based on the loading and foundation design assumptions of this report. If alternate foundations are proposed, additional recommendations can be provided upon request.

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It is recommended that footing excavations be observed by the project soils engineer prior to placing concrete reinforcing steel to confirm the subsurface conditions are similar to those described in this report.

9.2.1 Foundation Grade Soils Preparation

Foundations will be bottomed on densified structural fill placed/prepared in general accordance with Section 9.1.3 (Grading and Filling) and Section 9.5.1 (Remedial Earthwork). Foundations excavations should be cleaned of loose materials prior to the placement of reinforcing steel.

9.2.2 Isolated or Continuous Footings

The foundation design parameters presented in Table 8 (Foundation Design Parameters) can be utilized for the design of individual spread foundations and continuous wall footings.

Regardless of loading, individual column foundations and continuous spread foundations should be at least 18 inches wide and embedded at least 24-inches bgs, or as required by code.

Table 8 – Foundation Design Parameters

Allowable Bearing Pressures (psf) (1,2):

Footings bottomed at least 2 feet (3) below the finished grade on properly compacted structural fill

1,500

Allowable Friction Coefficient:

Between foundation bottom and supporting soil consisting of properly compacted structural fill

0.40

Allowable Passive Soil Pressure (psf) (1)

Backfill soils consisting of properly compacted structural fill

350(4)

(1) (psf)-Pounds per square foot

(2) The allowable bearing pressure may be increased by one-third for total loading conditions including wind and seismic forces (2012 IBC). The allowable bearing pressure is a net value; therefore, the weight of the foundation which extends below grade and backfill may be neglected when computing dead loads. The allowable bearing pressure includes a FOS of 3.0 against bearing failure.

(3) Allowable bearing pressures may be increased for foundations bottomed at greater depths. Once the final loads and footing elevations have been determined, the project geotechnical engineer should be contacted to evaluate the net allowable bearing pressure.

(4) The upper one-foot of the soils profile should be neglected when designing for passive pressure, unless confined by a concrete slab or pavement. Design values are based on footings backfilled with properly compacted structural fill.

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9.2.3 Concrete Slabs

All concrete slabs should be directly underlain by aggregate base material. Type 2 aggregate base is the preferred alternate, although other materials may be acceptable.

The thickness of base material should be at least 6 inches. Aggregate base courses should be densified to at least 95 percent relative compaction.

Subgrade soils shall be prepared in accordance with recommendations presented in the Foundation Grade Soils Preparation section of this report. If fine-grained soils (as described in this report) are encountered at the subgrade elevation, they should be completely removed or overexcavated to a depth of 1 foot (whichever is less) and replaced with densified structural fill. Additional laboratory testing should be conducted to confirm the plasticity characteristics of the subgrade soils.

Type II cement is recommended for project design. Due to the potential exposure to freeze/thaw conditions the project design engineer should consider air entrainment for the project mix design.

A coefficient of subgrade reaction (K-value) of 100 pounds per cubic inch should be used for design of concrete slabs. The design engineer should determine the slab thickness and structural reinforcing requirements based on the anticipated loading. All concrete floor slabs should have a minimum thickness of 4-inches.

Placement and curing should be performed in accordance with procedures outlined by the American Concrete Institute (ACI). Special considerations should be given to concrete placed and cured during hot or cold weather conditions. Proper control joints and reinforcing should be provided to minimize any damage resulting from shrinkage.

9.2.4 Lateral Resistance

Lateral loads (such as wind or seismic) may be resisted by passive soil pressure and friction at the bottom of the footing. A design value for passive soil pressure of 350 psf per foot of depth6 and a friction factor of 0.40 may be utilized for sliding resistance at the base of the footing. The friction coefficient of 0.40 assumes that structural elements will be bottomed on at least 2-feet of properly compacted structural fill.

Overturning moments and uplift loading can be resisted by the weight of the foundation, weight of the structure, and any soil overlying the foundation. A unit weight of 120 pounds per cubic foot may be assumed for backfill soils consisting of properly compacted structural fill.

9.2.5 Static Settlement

An elastic settlement response is expected for foundations bottomed on properly compacted structural fill or medium dense native granular material. The majority of the settlement is expected to occur rapidly, generally during the construction timeframe. For the purposes of this report, structural loads are anticipated to be light.

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Once loading is determined for the structure, settlement can be estimated. However, based on the loading assumptions of this report and the anticipated foundation grade material, settlement on the order of 1-inch or less is expected. Differential settlement for foundations with similar loads is anticipated to be about ½ of the total settlement provided the foundations are all bottomed on similar material (e.g. all on properly compacted structural fill).

9.2.6 Moisture Vapor Retarder

The transmission of moisture to the base of the slab can occur through two physical processes: water vapor transmission and/or capillary action of the underlying soils. Water vapor can be transmitted through the slab and the transmission rate depends on the difference in the water vapor pressure between the air voids in the slab and the air above the slab.