Geologic/Geotechnical Investigation St. Moritz at Heber 12

Intermountain GeoEnvironmental Services, Inc. 930 South State, Suite 50, Orem, Utah 84097 Phone (801) 224-8020 | Fax (801) 224-8023

www.igesinc.com

Geologic/Geotechnical Investigation St. Moritz at Heber 12-Acre Addition

Wasatch County, Utah

IGES Job No. 00277-014

October 16, 2002

Prepared for:

Epic Engineering, P.C.

TABLE OF CONTENTS

1.0 EXECUTIVE SUMMARY ...................................................................................1

2.0 INTRODUCTION..................................................................................................3

2.1 PURPOSE AND SCOPE OF WORK..................................................................3 2.2 PROJECT DESCRIPTION..................................................................................3

3.0 METHODS OF STUDY........................................................................................4

3.1 OFFICE RESEARCH..........................................................................................4 3.2 FIELD INVESTIGATION ..................................................................................4 3.3 SUBSURFACE INVESTIGATION....................................................................4 3.4 LABORATORY INVESTIGATION ..................................................................5 3.5 ENGINEERING ANALYSIS..............................................................................6

4.0 GENERALIZED SITE CONDITIONS ...............................................................8

4.1 SURFACE CONDITIONS ..................................................................................8 4.2 SUBSURFACE CONDITIONS ..........................................................................8

4.2.1 Soils..................................................................................................................8 4.2.2 Bedrock ............................................................................................................9 4.2.3 Groundwater/Moisture Content Conditions ....................................................9

5.0 GEOLOGIC CONDITIONS...............................................................................10

5.1 GEOLOGIC SETTING .....................................................................................10 5.2 SEISMICITY AND FAULTING ......................................................................10 5.3 OTHER GEOLOGIC HAZARDS.....................................................................11

5.3.1 Liquefaction ...................................................................................................12 5.3.2 Stream Flooding ............................................................................................12 5.3.3 Alluvial Fan Flooding/Debris Flow ..............................................................12 5.3.4 Canal/Ditch Flooding ....................................................................................14

6.0 ENGINEERING CONCLUSIONS AND RECOMMENDATIONS...............15

6.1 GENERAL CONCLUSIONS............................................................................15 6.2 EARTHWORK ..................................................................................................15

6.2.1 Site Preparation and Grading .......................................................................16 6.2.2 Excavations ....................................................................................................17 6.2.3 Excavation Stability .......................................................................................17 6.2.4 Structural Fill ................................................................................................17 6.2.5 Flooding/Debris Flow Hazard Mitigation.....................................................18 6.2.6 Cut and fill Slopes..........................................................................................19

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6.3 FOUNDATIONS ...............................................................................................19 6.4 LATERAL RESISTANCE AND LATERAL EARTH PRESSURES ..............20 6.5 ROADWAY PAVEMENT DESIGN ................................................................21 6.6 MOISTURE PROTECTION AND SURFACE DRAINAGE...........................21 6.7 PRELIMINARY SOIL CORROSION POTENTIAL .......................................22

7.0 CLOSURE ............................................................................................................23

7.1 LIMITATIONS..................................................................................................23 7.2 ADDITIONAL SERVICES...............................................................................23

8.0 REFERENCES CITED .......................................................................................25

APPENDIX

A Plate A-1 Site Vicinity Map Plate A-2 Site Aerial Photograph Plate A-3 Site Exploration Location Map Plate A-4a Site Vicinity Geologic Map Plate A-4b Site Vicinity Geologic Map Legend Plates A-5 to A-10 Boring and Test Pit Logs Plate A-11 Key to Soil Symbols and Terms Plate A-12 Summary of Geologic Hazards Table

Appendix B Plate B-1 Atterberg Limit Test Results Plate B-2 Grain Size Distribution Plate B-3 Consolidation Test Results Plate B-4 CBR and Proctor Test Results Plate B-5 Summary of Laboratory Test Results Table

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1.0 EXECUTIVE SUMMARY

This report presents the results of a geotechnical/geologic investigation conducted for the 12 acre addition to the proposed St. Moritz at Heber Site, in Wasatch County, Utah. The project site is located north of Heber City and south of Jordanelle Reservoir along the east side of Highway 40 and Moulton Lane. The area this report covers is an extension of the St. Moritz site that was previously investigated by IGES. The results of that geotechnical investigation are included in a final geotechnical report dated August 28, 2002. The purposes of this investigation were to assess the nature and engineering properties of the subsurface soils and bedrock at the proposed site and to provide recommendations for general site grading, excavation and the design and construction of foundations, slope stability and roadway pavement design. Based on the six test pits completed for this investigation, soil thicknesses at the subject site range between depths of 1 to over 9.5 feet. In general, the soils encountered within the test pits consisted of organic topsoil, Fat CLAY (CH), Lean CLAY (CL), SILT (ML), Silty SAND (SM), Sandy GRAVEL (GP), and Poorly Graded GRAVEL with silt and sand (GP-GM). These soils are generally 0.5 to over 5 feet thick Bedrock outcrops were not observed at the subject site during the fieldwork conducted for this investigation. Based on test pit exposures observed during the fieldwork completed for this project, bedrock was encountered in TP-9, TP-10, TP-11, and TP-12. Bedrock was observed to consist of volcanic tuff and volcaniclastic conglomerate of the Keetley Volcanics. Varying thicknesses of colluvium and fan alluvium cover this bedrock. Based on the subsurface conditions encountered at the site, it is our opinion that the subject site is suitable for the proposed construction provided that the recommendations presented in this report be properly implemented during design and construction. In general, the development can be completed using standard construction practices. The structures can be founded on conventional shallow spread footings using a bearing capacity that will minimize the potential for settlement in areas overlying softer soils. However, as described previously in this report, some of the near-surface soils were found to exhibit a low to moderate hydro-collapse potential. These soils were found to exist predominantly in the southern edge of the site. The other areas of the site contained shallow bedrock. In these collapse potential areas, we recommend a minimum of 18-inches of the native soils be reworked beneath footings and 12-inches beneath pavements and concrete flatwork to minimize the potential for hydro-collapse settlement to occur.

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There is a potential for debris flow and alluvial fan flooding at the site due to it’s proximity to a small canyon located northeast of the site. Because of this potential we recommend a detention basin be constructed at the mouth of the canyon. If a detention basin cannot not be completed in a timely manner, a berm or some other barrier may be constructed along the north side of Moulton Lane to divert flood waters away from the site and channel it down the roadway. We anticipate that the majority of the site will be easily excavated with conventional construction equipment. However, shallow bedrock is anticipated in the northern two-thirds of the site. In general, the near surface bedrock is weathered and relatively soft, but becomes more competent with depth. Excavation in the weathered portions of bedrock can likely be completed with conventional construction equipment. However, as the rock becomes more competent with depth and in localized areas, special construction equipment may be required. The use of heavy-duty track-hoes and/or dozers with ripper-teeth and/or drilling and blasting may be required in some areas. Conventional strip and spread footings constructed on a zone of reworked fine-grained native soil or on relatively undisturbed, non-collapsible native soil may be proportioned using a maximum net allowable bearing pressure of 2,000 pounds per square foot (psf). NOTICE: The scope of services provided within this report are limited to the assessment of the subsurface conditions for the proposed development. This executive summary is not intended to replace the report of which it is part and should not be used separately from the report. The executive summary is provided solely for purposes of overview. The executive summary omits a number of details, any one of which could be crucial to the proper application of this report.

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2.0 INTRODUCTION

2.1 PURPOSE AND SCOPE OF WORK

This report presents the results of a geotechnical/geologic investigation conducted for the 12 acre addition to the proposed St. Moritz at Heber Site, in Wasatch County, Utah. The project site is located north of Heber City and south of Jordanelle Reservoir along the east side of Highway 40 and Moulton Lane. The area this report covers is an extension of the St. Moritz site that was previously investigated by IGES. The results of that geotechnical investigation are included in a final geotechnical report dated August 28, 2002. The purposes of this investigation were to assess the nature and engineering properties of the subsurface soils and bedrock at the proposed site and to provide recommendations for general site grading, excavation and the design and construction of foundations, slope stability and roadway pavement design. The scope of work completed for this study included a site reconnaissance, subsurface exploration, soil sampling, geophysical survey, laboratory testing, engineering analyses, and preparation of this report. Our services were performed in accordance with our discussions with you.

2.2 PROJECT DESCRIPTION

The project site is located on approximately 12 acres of undeveloped land east of Highway 40, north of Heber City, Utah. The project site is shown on the Site Vicinity Map and the Site Aerial Photograph included in Appendix A of this report (Plates A-1 and A-2). The site lies east of the Wasatch Canal along the north side of Moulton Lane. We understand this portion of the St. Moritz at Heber project consists of approximately 12 acres that will be used for Multi-family Residential housing and commercial buildings with associated features including roadways and landscaping. We anticipate minor to moderate cuts and fills, on the order of 8 feet or less, will be required based on the site location and topography. We anticipate structural loading will be typical of multi-family residential dwellings with wall loads on the order of 5000 to 7000 pounds per lineal foot. The project site is shown on the Site Vicinity Map included in Appendix A (Plate A-1) and on the Site/Exploration Location Map (Plate A-3).

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3.0 METHODS OF STUDY

3.1 OFFICE RESEARCH

An engineering geologist investigated the geologic conditions at the subject site. A literature review was conducted which consisted of reviewing previous geologic reports of the area and other available geologic literature and geologic maps pertinent to the site, as indicated in the references cited. Stereographic aerial photograph interpretation was performed for the site using photographs provided to IGES by the USDA-FSA, Aerial Photography Field Office. Two sets of three 9 x 9 inch photographs dated 8/1/62 and 7/8/97 were studied for this report.

3.2 FIELD INVESTIGATION

A field geologic reconnaissance was conducted to observe existing geologic conditions and to evaluate existing and potential geologic hazards. The findings of the geologic investigation are presented in Sections 4.0 and 5.0 of this report. Based on the geologic reconnaissance, 6 locations were selected for subsurface investigation by means of test pits. Based on our geologic/geotechnical report and associated site geologic reconnaissance for the St. Moritz 50 Acre Site, it was observed that there might be potential alluvial fan flooding/debris flow hazards at the site. An experienced Engineering Geologist from our staff visited the site and viewed aerial photographs to assess these potential hazards and identify areas that could be used for detention, diversion or channeling. The findings from this evaluation are presented later in this report.

3.3 SUBSURFACE INVESTIGATION

As a part of this investigation, subsurface soil conditions were explored by excavating six test pits across the site. The locations of the test pits are shown on the Site Plan (Plate A-3). A qualified engineering geologist visually logged soils in the test pits at the time of excavation according to the Unified Soil Classification System (USCS). The test pits were completed up to 9 feet below the existing site grade. Logs of the test pits are included at the end of this report (Plates A-5 thru A-10). A Key to Soil Symbols and Terms is also provided as Plate A-11. The geophysical information obtained at the site is contained in Appendix C and is further discussed

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in Section 6.0 of this report Test pits, approximately 10 feet long by 3 feet wide, were excavated by use of a rubber-tired backhoe. Representative samples of the soils encountered in the test pits were collected and classified by the field geologist, and portions of each sample were packaged and transported to our laboratory for testing.

3.4 LABORATORY INVESTIGATION

Representative soil samples taken from the test pits were tested in the laboratory to evaluate pertinent physical and engineering properties. Laboratory soil tests consisted of moisture, density, gradation, Atterberg limits, and consolidation/collapse to aid in characterizing the soils. Soil solubility tests were completed to assess the potential for dissolution of soil mineral matter with water. Soluble sulfate and resistivity tests were completed to provide a preliminary assessment of the soil corrosion potential. A moisture density relationship (ASTM D-698 Method B) and a California Bearing Ratio (CBR) test were completed to assess the strength of the pavement subgrade soils. The results of all laboratory tests are presented on the Test Pit Logs in Appendix A (Plates A-5 to A-10), in the lab results in Appendix B (Plates B-1 to B-4) and in the Summary of Laboratory Test Results Table (Plate B-5). Results of the laboratory tests indicate that the on-site soils have dry unit weights ranging from approximately 85.5 to 100.4 pounds per cubic foot (pcf) in the in-situ soils. The subsurface soils moisture content ranged from a low of 5.9% to a high of 16.3%. The moisture content generally increased with depth. Atterberg limit tests indicate that the soils plasticity index ranged from a low of 10 to a high of 45. The fine-grained site soils classified as Fat CLAY (CH), Lean CLAY (CL), and SILT (ML) as noted in the test pit logs. Consolidation/collapse tests indicate that the site soils have a minor to moderate potential to collapse under increased moisture and loading conditions. The collapse potential under a 2,000 psf load was 1.77% to 3.85%. Consolidation tests completed in conjunction with the collapse test indicate the site soils are moderately compressible under increased loading. Results of the CBR test indicate that the near surface site soils will provide relatively fair to poor support for roadway pavements. A CBR value of 4.1 was obtained for the near surface soils.

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Results of the soil solubility test indicate that the site soils have a low potential for dissolution of soil mineral matter under increased moisture conditions. The soil solubility of the Silty SAND in Test Pit 14 is 0.21%. As a preliminary indication of the soil corrosion potential, a soil soluble sulfate content of 20 mg/kg, a pH of 7.9 and a minimum resistivity of 7650 ohm-cm were obtained in the laboratory for a sample of the soil taken from TP-1 at a depth of 6 feet. Soil samples are normally discarded 30 days after submittal of the report unless IGES, Inc. receives a specific request to retain the samples for a longer period of time.

3.5 ENGINEERING ANALYSIS

Based on the proposed construction at the site, the following engineering analyses were performed:

• Excavatibility • Excavation stability • Bearing capacity of foundation soils • Foundation settlement • Lateral earth pressures against foundations, basement and retaining walls • Lateral resistance against sliding • Pavement design • Preliminary Corrosion Assessment

Engineering analyses were performed using soil data obtained from the laboratory test results and empirical correlations from material density, depositional characteristics and classification. Appropriate factors of safety were applied to the results consistent with industry standards and the accepted standard of care. Excavatibility and excavation stability were evaluated based on the excavation conditions encountered and the laboratory test results. For excavation stability, OSHA minimum requirements are typically followed unless conditions warrant further flattening of slopes. Bearing capacity values were calculated using Hansen’s modifications to Terzaghi’s original

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bearing capacity formula. Strength parameters for the bearing soils were assigned based on the laboratory test data, field data and observations. A factor of safety of 3 was used in developing allowable bearing values. Bearing capacities were also limited to minimize settlement of foundation elements. For the fine grained soils, an undrained shear strength value of 700 psf and a friction angle of 0 degrees were used based on the laboratory test results for the fine-grained soils. For the coarse grained soils a shear strength of 0 psf and a friction angle of 35 degrees was used. Settlement in the fine-grained soils at the site was estimated using Terzaghi’s (1925) one-dimensional consolidation theory which uses laboratory derived soil properties of compression, recompression, and over-consolidation to estimate settlement based on induced vertical stress. Influence factors from Boussinesq were used to evaluate the increase in vertical stress and the stress distribution below footings. Lateral earth pressures were calculated using Rankine’s lateral active and passive earth pressures based on an assumed internal friction angle for the material. At rest lateral earth pressures were calculated using equations proposed by Jaky (1944). A friction angle of 26 degrees was estimated based on the empirical data, field observations and published test results for compacted soils from the Bureau of Reclamation (1982). Lateral resistance against sliding was evaluated using published information pertaining to the relationship between the internal friction angle values and soil type against concrete. Pavement design was completed using Pavement Analysis Software (PAS). PAS uses standard methods to evaluate both Portland Cement Concrete and Asphalt Concrete pavements. A California Bearing Ratio (CBR) of 4.1 was established in the laboratory and used in the program to define the strength of the subgrade soils. A preliminary corrosion assessment was completed based on the laboratory test results obtained from the Soluble Sulfate, pH and Resistivity tests performed on a representative sample. Information provided in the Navy’s design manual, Navdocks DM-5 was referenced.

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4.0 GENERALIZED SITE CONDITIONS

4.1 SURFACE CONDITIONS

The subject site consists primarily of an open, undeveloped field that slopes moderately to the west. A private residence is located along the east margin of the subject site. Moulton Lane runs along the southern property boundary and the Wasatch Canal runs along the western property boundary. Undeveloped land that is part of the St. Moritz 50-acre property borders the subject site to the north. The site is vegetated with sagebrush, grasses, and occasional juniper trees. No surface water was observed on or adjacent to the subject site during the fieldwork conducted for this investigation.

4.2 SUBSURFACE CONDITIONS

As previously mentioned, the subsurface soil conditions were explored at the subject property by excavating 6 test pits across the site. The depths of the test pits ranged between 2.5 to 10 feet below the existing natural site grade. Refusal was encountered in three of the test pits due to the shallow bedrock conditions over portions of the site. Subsurface soil conditions were logged at the time of trenching and are included in the Test Pit Logs in Appendix A (Plates A-5 to A-10). The soil and moisture conditions encountered, during our investigation, are discussed below.

4.2.1 Soils

Based on the explorations completed for this investigation, soil thicknesses at the subject site range between depths of 1 to over 9.5 feet. In general, the soils encountered within the test pits consisted of organic topsoil, Fat CLAY (CH), Lean CLAY (CL), SILT (ML), Silty SAND (SM), Sandy GRAVEL (GP), and Poorly Graded GRAVEL with silt and sand (GP-GM). These soils are generally 0.5 to over 5 feet thick. A more detailed description of these sediments is presented on the test pit and boring logs found on Plates A-5 to A-10. The stratification lines shown on the enclosed Test Pit logs represent the approximate boundary between soil types. The actual in-situ transition may be gradual. Due to the nature and depositional characteristics of the native soils, care should be taken in interpolating subsurface conditions between and beyond the exploration locations.

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4.2.2 Bedrock

Bedrock outcrops were not observed at the subject site during the fieldwork conducted for this investigation. Based on test pit exposures observed during the fieldwork completed for this project, bedrock was encountered in TP-9, TP-10, TP-11, and TP-12. Bedrock was observed to consist of volcanic tuff and volcaniclastic conglomerate of the Keetley Volcanics. Varying thicknesses of colluvium and fan alluvium cover this bedrock.

4.2.3 Groundwater/Moisture Content Conditions

Groundwater was not encountered in any of the test pits within the depths explored for this investigation. The soil moisture content ranged from a low of 5.9% to a high of 16.3%. Seasonal fluctuations in precipitation, surface runoff from adjacent properties, or other on or offsite sources may also increase moisture conditions at the site. Due to the season of our investigation, we anticipate groundwater levels to be near their seasonal low.

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5.0 GEOLOGIC CONDITIONS

5.1 GEOLOGIC SETTING

The subject site is located at an elevation between approximately 5720 to 5802 feet in an area described by Stokes (1986) as the Hinterlands portion of the Rocky Mountains physiographic province and is situated between the Wasatch and Uinta Mountains at the northern end of the Heber Valley (Plate A-1). The Heber Valley is a sediment-filled, erosional valley located on the eastern side of the Wasatch Mountains, in the central portion of Utah (Hintze, 1980; Bryant, 1992; Bryant, 1990). Water from the Uinta Mountains is carried east across the Heber Valley and through the Wasatch Mountains by the Provo River. The elevation of the Wasatch Mountains relative to the elevation of the Heber Valley has caused the impedance of the flow of the Provo River, resulting in a low stream gradient and causing the river to meander (Baker, 1976). Lateral planation of the valley by the meandering river eroded softer Mesozoic rocks and Tertiary volcanic rocks, resulting in the widening evolution of the Heber Valley. The impedance of the flow of the Provo River has also led to the deposition of large quantities of Quaternary fluvial sediments that now fill much of the Heber Valley. Surface sediments at the subject site are mapped as Holocene and Pleistocene valley alluvium consisting of boulders to pebble gravel, sand, silt, and clay deposited in channels and flood plains of streams and alluvial fan and debris fan deposits consisting of gravel, sand, and silt, locally bouldery (Bromfield and others, 1970; Bryant, 1990; Plates 4a and 4b). Bedrock underlying these sediments and outcropping throughout portions of the site is mapped as Oligocene and Eocene Keetley Volcanics consisting of light-gray to gray lahar, flow breccia, and tuff.

5.2 SEISMICITY AND FAULTING

The site lies on the east side of the north-south trending belt of seismicity known as the Intermountain Seismic Belt (ISB) (Hecker, 1993). The ISB extends from northwestern Montana through southwestern Utah. No active faults are reported to run through or immediately adjacent to the site. The site is located approximately 23 miles northwest of the Strawberry fault. The Strawberry fault has a reported rupture length of 17.4 miles and a maximum potential of magnitude 7.0. The most recent activity on the Strawberry fault is reported to be early to middle Holocene. The site is also approximately 19 miles east of the Salt Lake City segment of the Wasatch fault zone. The Salt Lake City segment is reported to be active and thought to generate

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earthquakes of approximate magnitude 7.0 to 7.5 every 1350 ± 200 years (Black and others, 1995). The Round Valley fault is located approximately 7.5 miles south of the site and is reported to be of late Quaternary age (Hecker, 1993; Hylland and others, 1995). The Round Valley fault has a reported maximum potential magnitude of 6.5 to 6.75 (MS). Although this fault is not considered active (Hylland and others, 1995) mapped a special study area for critical facilities planned to be built adjacent to the fault. The expected maximum ground acceleration from a large earthquake at the subject site with a two (2) percent probability of exceedance in 50 years is 0.33g (United States Geological Survey’s (USGS) Earthquake Hazards Program - National Seismic Hazard Mapping Project). These values are estimated ground surface accelerations for a “firm rock” site, which is identified as having a shear-wave velocity of 760 m/sec (2,500 feet/sec) in the top 30 meters (100 feet). Sites with different soil types may experience amplification or de-amplification of these values. The site is situated within the International Building Code (IBC) Region 2. Based on our field investigation, it is our opinion the soils at this site are representative of a “rock” profile having an average shear-wave velocity of 2,500 ≤ ῡS ≤ 5,000 (ft/sec) in the top 100 feet, best represented by IBC Site Class B having Site Coefficients of Fa= 1.0 and Fv=1.0.The following table reports the ground motion from the values obtained from the USGS website for the subject site. LOCATION 40.5524º Latitude -111.4186º Longitude Distance to nearest grid point 5.5 kilometers Nearest grid point 40.6º Latitude -111.4º Longitude Probabilistic ground motion values, in percent g, at the nearest grid point are: 10% Probability of

Exceedance in 50 Years 5% Probability of

Exceedance in 50 Years 2% Probability of

Exceedance in 50 Years PGA 16.23 22.51 32.76 0.2 sec SA 37.38 51.73 78.70 1.0 sec SA 12.29 17.94 27.18

5.3 OTHER GEOLOGIC HAZARDS

Geologic hazards can be defined as naturally occurring geologic conditions or processes that could present a danger to human life and property. These hazards must be considered before development of the site. There are several hazards in addition to seismicity and faulting that may be present at the site, and which should be considered in the design of habitable structures and other critical infrastructure. Other geologic hazards considered significant for this site include liquefaction, stream flooding, alluvial fan flooding/debris flow, and Canal/Ditch Flooding. A

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complete list of potential geologic hazards is included in the Summary of Geologic Hazards Table in Appendix A of this report (Plate A-12).

5.3.1 Liquefaction

Certain areas within the Intermountain region also possess a potential for liquefaction during seismic events. Liquefaction is a phenomenon whereby loose, saturated, granular soil deposits lose a significant portion of their shear strength due to excess pore water pressure buildup resulting from dynamic loading, such as that caused by an earthquake. Among other effects, liquefaction can result in densification of such deposits causing settlements of overlying layers after an earthquake as excess pore water pressures are dissipated. The primary factors affecting liquefaction potential of a soil deposit are: (1) level and duration of seismic ground motions; (2) soil type and consistency; and (3) depth to groundwater. Based on the field data collected for this site the potential for liquefaction is considered low.

5.3.2 Stream Flooding

Stream flooding is a hazard related to spring snowmelt, run-off and flash–flooding from summer rainstorms. Flood hazards should be considered when planning for the development of habitable structures and essential and critical facilities located within areas having a potential flood risk. There are no stream flooding hazards reported at the subject site (Hylland and others, 1995), nor were any observed during the fieldwork conducted for this report. There are no streams located at the subject site and the site is located above the Provo River flood plain. However, an ephemeral stream exits the dry canyon above the subject site and drains towards the site. Run-off during rainstorms and snowmelt may collect in this dry canyon and drain onto the subject site resulting in alluvial fan flooding. A discussion of this hazard follows.

5.3.3 Alluvial Fan Flooding/Debris Flow

Alluvial fan flooding is a potential hazard that may exist on areas mapped as Holocene alluvial fans. This type of flooding typically occurs as a debris flood consisting of a mixture of soil, organic material, and rock debris transported by fast-moving flood water. Debris floods and debris flows can be a hazard on alluvial fans or in stream channels above alluvial fans. Just like with stream flooding, debris floods and debris flows can occur as a result of runoff from spring snowmelt and cloudburst rainstorms. Landslides can also mobilize a debris flow.

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The surface sediments at the subject site are mapped as part of a Holocene to Pleistocene alluvial fan deposit (Bryant, 1990; Hylland and others, 1995). There is a potential alluvial fan flood/debris flow hazard associated with this alluvial fan (Plate A-2). This alluvial fan consists of sediment divulged onto the valley floor from the dry wash that exits the canyon east of the site. Water and sediment exiting the canyon will first have to overrun the Timpanogos Canal, which crosses the mouth of the canyon. The Timpanogos Canal is 4 to 6 feet wide and 4 to 6 feet deep. If enough water and sediment exit the canyon to fill in and overtop the Timpanogos canal, then the flow would likely continue in the existing channel, which is down-cut into the alluvial fan. Drainage in this channel is directed into a culvert that runs under the driveway of the house adjacent to the east boundary of the subject site. This culvert does not appear to be large enough to convey coarse debris flow sediments through it. This culvert, in our opinion, would likely become blocked off during a large debris flow event. The flow of sediment and water west of this driveway would become mostly a sheet flow as the existing channel becomes less defined. If sediment were to flow over the existing driveway it would cross the medial portion of the subject site along an existing topographic low (Plate A-2). It should be noted that after observing the existing channel and the grading of the private driveway on the residence to the east of the site it is our opinion that debris flow sediments may likely flow over Moulton Lane and traverse to the west on the south side of the street. An earthern berm approximately 4 feet high has been constructed along the south side of Moulton Lane. The slope of the alluvial fan surface within the subject site is relatively gentle and sediments exposed in the upper 9.5 feet of our explorations consisted of gravel, sand, silt, and clay. Due to the nature of the sediments observed in this portion of the site and the slope of the alluvial fan it is our opinion that the hazard associated with debris flows and alluvial fan flooding at the subject site would consist of water and mud flooding. While these hazards would cause flooding of basements and damage to landscaping, they would not pose a significant hazard to structures or human life. An additional hazard of concern related to alluvial fan flooding and debris flows on this alluvial fan would be flooding of the Timpanogos and Wasatch Canals resulting from overcapacity due to the addition of excess floodwater or plugging off of the canals by debris flow sediments. Both of these canals are up-gradient of Heber City and if floodwater were to enter these canals then canal flooding could occur in other areas along the Timpanogos and Wasatch Canals. It would be appropriate for Wasatch County to consider assessing the alluvial fan flooding and debris flow hazards associated with this canyon and to potentially construct a detention/debris basin in the

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mouth of the canyon to mitigate any potential alluvial fan flooding and debris flow hazards. A detention basin in the mouth of the canyon would mitigate alluvial fan flooding and debris flow hazards for several existing homes and other developable land as well as the subject site and would reduce the risk of canal flooding in other areas along the Timpanogos and Wasatch Canals. It should also be noted that development of land between the subject site and the mouth of the canyon could render mitigation on the subject site ineffective or unnecessary.

5.3.4 Canal/Ditch Flooding

The Timpanogos Canal is located uphill from the site and the Wasatch Canal runs along the western boundary of the subject site. High flows in these canals may cause flooding that could impact the site. Failure of the canal embankments or, as mentioned previously, a blockage in the canal could also cause flooding and impact the site facilities. The Timpanogos Canal, uphill of the site, has recently been placed in a concrete channel, which will reduce the potential for embankment failure.

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6.0 ENGINEERING CONCLUSIONS AND RECOMMENDATIONS

6.1 GENERAL CONCLUSIONS

Based on the subsurface conditions encountered at the site, it is our opinion that the subject site is suitable for the proposed construction provided that the recommendations presented in this report be properly implemented during design and construction. In general, the development can be completed using standard construction practices. The structures can be founded on conventional shallow spread footings using a bearing capacity that will minimize the potential for settlement in areas overlying softer soils. However, as described previously in this report, some of the near-surface soils were found to exhibit a low to moderate hydro-collapse potential. These soils were found to exist predominantly in the southern edge of the site. The other areas of the site contained shallow bedrock. In these collapse potential areas, we recommend a minimum of 18-inches of the native soils be reworked beneath footings and 12-inches beneath pavements and concrete flatwork to minimize the potential for hydro-collapse settlement to occur. There is a potential for debris flow and alluvial fan flooding at the site due to it’s proximity to a small canyon located northeast of the site. Because of this potential we recommend a detention basin be constructed at the mouth of the canyon. If a detention basin cannot not be completed in a timely manner, a berm or some other barrier may be constructed along the north side of Moulton Lane to divert flood waters away from the site and channel it down the roadway. The following sub-sections present our recommendations for general site grading, design of foundations, slabs-on-grade, lateral earth pressures and moisture protection and soil corrosion.

6.2 EARTHWORK

Prior to the placement of foundations, general site grading is recommended to provide proper support for foundations, exterior concrete flatwork, concrete slabs-on-grade, and asphalt pavement sections. Site grading is also recommended to provide proper drainage and moisture control on the subject property and to aid in preventing differential movement in foundation soils as a result of variations in moisture conditions.

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6.2.1 Site Preparation and Grading

Within the areas to be graded (below proposed structures and fill sections), any existing vegetation, debris, and fill soils should be removed. Based on our observations grubbing approximately 6 to 10 inches should remove the major vegetation zone at the site. Any loose or disturbed soils beneath these areas should also be removed or compacted in place as outlined in Section 6.2.4. Following the removal of vegetation, debris, and loose or disturbed soils, as described above, site grading may be conducted to bring the site to grade. Based on the presence of soils with a moderate potential for hydro-collapse, we recommend that special site grading conditions be implemented to minimize the potential settlement associated with these soils. These special-grading conditions include sloping the ground surface immediately adjacent to structures so as to drain water away from the foundations. Additionally, grading should include creating a zone of reworked native soils beneath all foundations, slabs-on-grade construction and pavements in the southern portion of the site. The Geotechnical Engineer should be present to identify the extent of the collapsible soil and what areas should be reworked and do not need reworking. The zone of reworked native soils should be a minimum of 1.5-feet thick beneath building foundations and 1-foot beneath slabs-on-grade, curb and gutter and pavements. It should be noted that by only re-working portions of the hydro-collapsible soil profile would potentially leave several feet of similar soils in place. If these soils become saturated, foundations, roadways and embankments may experience excessive settlement. As an alternative to reworking the upper zone of native soil, all of the collapsible soils could be reworked or removed and replaced with structural fill, or deep foundations such as helical piers, cast-place-concrete piers and piles may be used to extend the foundation loads below the collapsible soil or to at least by-pass the largest portion of these deposits. Typically these foundations would need to extend 10 to 20 feet or until bedrock or a gravel layer is encountered. The acceptable level of risk should be considered by the Owner/Developer and the amount of effort used to mitigate the hydro-collapsible soils at the site be established. If surface grading is completed to divert water away from foundations and other measures are taken, the risk can be greatly reduced. These measures are discussed further in future sections of this report.

© 2002 IGES, Inc. 16 R0277-014

6.2.2 Excavations

As previously noted, the majority of the soils consist of bedrock overlain by varying thicknesses of sands, clays and gravels. We anticipate that the majority of the site will be easily excavated with conventional construction equipment. However, shallow bedrock is anticipated in the northern two-thirds of the site. In general, the near surface bedrock is weathered and relatively soft, but becomes more competent with depth. Excavation in the weathered portions of bedrock can likely be completed with conventional construction equipment. However, as the rock becomes more competent with depth and in localized areas, special construction equipment may be required. The use of heavy-duty track-hoes and/or dozers with ripper-teeth and/or drilling and blasting may be required in some areas. The contractor should satisfy himself/herself as to the ease of rock excavation throughout the project.

6.2.3 Excavation Stability

Based on Occupational Safety and Health (OSHA) guidelines for excavation safety, trenches with vertical walls up to 5 feet in depth may be occupied. Using the soil strength parameters obtained, our calculations support this. However, in areas where very moist soils are present or if groundwater rises to within the upper 5 feet, there may be some sloughing in of the trench sides that may endanger occupants. Where very moist soil conditions or if high groundwater is encountered in trenches shallower than 5 feet, or when the trench is deeper than 5 feet, we recommend a trench-shield or shoring be used as a protective system to workers in the trench. Sloping of the sides at 3/4H to 1V (45 degrees) in accordance with OSHA Type A soils may be used as an alternative to shoring or shielding. A qualified person should inspect all excavations frequently to evaluate stability. The Contractor is ultimately responsible for trench and site safety. Pertinent OSHA requirements should be met to provide a safe work environment.

6.2.4 Structural Fill

All fill placed for the support of structures, flatwork or pavements, is considered structural fill. The onsite silty sand and lean clay soils should be used as structural fill in collapse prone areas. On-site gravels or imported granular borrow may be used as structural fill in non-collapse prone areas. The Geotechnical Engineer should be on-site to identify the areas of collapse and non-collapse potential.

© 2002 IGES, Inc. 17 R0277-014

Structural fill should be free of vegetation and debris, and contain no inert materials larger than 3-inches in nominal size. All structural fill should be 1-inch minus material when within 1 foot of any base coarse material. Structural fill should be placed in maximum 12-inch loose lifts and compacted on a horizontal plane, unless otherwise approved by the Geotechnical Engineer. Lift thickness should be decreased to 8-inches in trenches or other areas where lighter compaction is used. Reworked native soils and fill placed beneath all footings, exterior flatwork and pavements should be compacted to at least 95% of the maximum dry density, as determined by ASTM D-1557. The moisture content should be within 2 percent of optimum to minimize the amount of compaction effort required and reduce the potential for swelling or settling. Moisture should be added prior to placement or mixed in place to provide a more uniform moisture content and better workability. Any imported fill materials should be approved prior to importing. Also, prior to placing any fill, the excavations should be observed by the Geotechnical Engineer to confirm that unsuitable materials have been removed. In addition, proper grading and subgrade proof-rolling should precede placement of fill, as described in the General Site Preparation and Grading subsection of this report. Backfill soils placed in utility trenches below pavement sections, curb and gutter and sidewalks should be backfilled with structural fill compacted to at least 95% of the maximum density. All other trenches, including landscape areas, should be backfilled and compacted to at least 90% of the maximum density. Backfill around basement and retaining walls should be compacted to a minimum of 90% of the maximum density as determined by ASTM D-1557. Only small compaction equipment should be used near basement and retaining walls.

6.2.5 Flooding/Debris Flow Hazard Mitigation

There is a potential for debris flow and alluvial fan flooding at the site due to it’s proximity to a small canyon located northeast of the site. Because of this potential we recommend a detention basin at the mouth of the canyon be considered. Since the land at the mouth of the canyon is not owned by the Client and because the potential hazard impacts several landowners, Wasatch County should coordinate efforts to construct a debris basin. If construction of a detention basin cannot be accomplished in the time required for this project, we recommend a berm or some other barrier be constructed along the north side of Moulton Lane to divert flood waters and

© 2002 IGES, Inc. 18 R0277-014

debris flow sediment away from the site and channel it down the roadway. A hydrologic and geologic study, separate from the requirements set on this project, should be completed in the canyon to assess the specifics of flooding and debris flows that may originate there. The assessment should provide information that will facilitate the design of detention facilities and/or provide information for establishing berm heights, lengths and locations. If the study cannot be completed in time to facilitate construction of the St. Moritz project, a temporary basin or berm may be completed to provide some protection from the potential hazards. UGS, Wasatch County and possibly IGES should all be involved in developing these temporary structures.

6.2.6 Cut and fill Slopes

Based on the soil types encountered at the site, we anticipate that cut and fill slopes may be constructed at 2H:1V horizontal to vertical. Steeper cuts can be created in areas where the slope will consist of bedrock. Flatter slopes may be required to minimize the potential for erosion. The planned cuts and fill on this portion of the site were not made available to IGES at the time this report was prepared, therefore the Geotechnical Engineer should be consulted on a case by case basis to provide recommendations for steepness of proposed cut and fill slopes planned to be steeper than 2H:1V.

6.3 FOUNDATIONS

Conventional strip and spread footings constructed on a zone of reworked fine-grained native soil or on relatively undisturbed, non-collapsible native soil may be proportioned using a maximum net allowable bearing pressure of 2,000 pounds per square foot (psf). All foundations exposed to the full effects of frost should be established at a minimum depth of 36-inches below the lowest adjacent final grade. Interior footings, not subjected to the full effects of frost, may be established at higher elevations, however, a minimum depth of embedment of 12 inches is recommended for confinement purposes. The minimum recommended footing width is 18 inches for continuous wall footings, 24 inches for isolated column footings and 12 inches for interior wall footings Settlements of properly designed and constructed conventional foundations, founded as described above, are anticipated to be less than ¾ of an inch. Differential settlements should be on the order of ½ the total settlement. However, if recommendations are not followed to place the required zone of compacted native soil beneath the footings, provide drainage away from the structures, downspouts are not discharged away from foundations, or excessive

© 2002 IGES, Inc. 19 R0277-014

irrigation occurs next to the foundation, the collapsible soils left beneath the foundations may increase total and/or differential settlements up to 2 inches or more. This amount of settlement could cause structural damage and it is imperative that all recommendations pertaining to the zone of compacted native soil and moisture protection presented in this report be complied with.

6.4 LATERAL RESISTANCE AND LATERAL EARTH PRESSURES

Lateral forces imposed upon conventional foundations due to wind or seismic forces may be resisted by the development of passive earth pressures and friction between the base of the footing and the supporting soils. In determining the frictional resistance, a coefficient of friction of 0.50 for structural fill (reworked native soils) against concrete should be used. Ultimate lateral earth pressures from natural soils and backfill acting against retaining walls and buried structures may be computed from the lateral pressure coefficients or equivalent fluid densities presented in the following table:

Condition Lateral Pressure Coefficient

Equivalent Fluid Density (pounds per cubic foot)

Active 0.39 43 At-rest 0.56 62 Passive 2.6 282

These coefficients and densities assume level, granular backfill with no buildup of hydrostatic pressures. The force of the water should be added to the presented values if hydrostatic pressures are anticipated. Additionally, if sloping backfill is present, the additional surcharge created by the wedge of soil should be added to the presented values. If sloping backfill is present, we recommend the Geotechnical Engineer be consulted to provide more accurate lateral pressure parameters once the design geometry is established. Walls and structures allowed to rotate slightly should use the active condition. If the element is constrained against rotation, the at-rest condition should be used. These values should be used with an appropriate factor of safety against overturning and sliding. A value of 1.5 is typically used. Additionally, if passive resistance is calculated in conjunction with frictional resistance, the resultant should be reduced by ½.

© 2002 IGES, Inc. 20 R0277-014

6.5 ROADWAY PAVEMENT DESIGN

Based on soil classifications and a laboratory obtained CBR value of 4.1, near surface soils are expected to provide fair to poor pavement support when properly compacted. Anticipated traffic volumes were not available at the time this report was prepared. However, based on our understanding of the project development we assumed traffic in the residential areas would consist of approximately 1000 passenger vehicles per day with 1 percent trucks and a 1.5 percent growth rate over a 20 year design period. Based on the CBR value and the assumed traffic information, the recommended pavement thickness is:

Asphalt Concrete (in.)

Untreated Road Base (in.)

Granular Borrow (in.)

3 9 6

Asphalt has been assumed to be a high stability plant mix and base course material composed of crushed stone with a minimum CBR of 70. Granular borrow material should consist of a pit run gravel, with a minimum CBR value of 30. The granular borrow material may be comprised of the on-site granular soils provided material larger than 4-inches has been removed and the minimum CBR value of 30 is confirmed. Subgrade preparation should be performed as discussed in the Sections 6.2.1 and 6.2.4 of this report, which consists of a minimum of 1-foot of reworked native soils compacted to a minimum of 95 percent of ASTM D-1557. If final anticipated traffic loading conditions vary significantly from our stated assumptions, IGES should be contacted so we can modify our pavement sections accordingly. Also, if perimeter roads are to contain heavier loading from “pass through” traffic, then the pavement thickness should be increased to accommodate these conditions.

6.6 MOISTURE PROTECTION AND SURFACE DRAINAGE

Due to the collapse potential of the on-site soils in portions of the site, planning and care should be implemented in the site drainage and design of surface water conveyance structures. Moisture should not be allowed to infiltrate the soils in the vicinity of the foundations and pavements. We recommend roof runoff devices be installed to direct all runoff a minimum of 15 feet away from structures and preferably day-lighted to the curb where it can be transferred to the storm drain system. We would also recommend storm drain collection sumps not be located adjacent to

© 2002 IGES, Inc. 21 R0277-014

foundations or within roadway pavements due to the presence of collapsible soils. We recommend drainage ditches adjacent to roadways be placed as far away from the pavement as practical and be lined with concrete or some other low permeability liner. To further aid in minimizing the potential for saturating soils beneath foundation elements, we recommend that all backfill soils around basement walls consist of low permeability fine-grained soils and be compacted to a minimum of 90% of the maximum density as determined by ASTM D1557.

6.7 PRELIMINARY SOIL CORROSION POTENTIAL

Soluble sulfate, resistivity and pH laboratory tests were completed to assess the potential for corrosion due to the chemistry of the native soils. It was found that the existing soils have a low degree of sulfate attack with concrete. Based on these results, we recommend a conventional Type I/II Cement be used in all concrete in contact with site soils. Metal corrosion was evaluated based on the resistivity test conducted. The results of the test indicate the on-site soils have little to no corrosiveness towards metal. However, because these results are preliminary, we recommend a corrosion engineer be consulted as necessary to develop site specific recommendations for expendable thickness or cathodic protection for underground, exposed metal piping.

© 2002 IGES, Inc. 22 R0277-014

7.0 CLOSURE

7.1 LIMITATIONS

The recommendations contained in this report are based on limited field exploration, laboratory testing, and our understanding of the proposed construction. The subsurface data used in the preparation of this report were obtained from the explorations made for this investigation. It is possible that variations in the soil and groundwater conditions could exist between the points explored. The nature and extent of variations may not be evident until construction occurs. If any conditions are encountered at this site that are different from those described in this report, our firm should be immediately notified so that we may make any necessary revisions to recommendations contained in this report. In addition, if the scope of the proposed construction changes from that described in this report, our firm should also be notified. This report was prepared in accordance with the generally accepted standard of practice at the time the report was written. No warranty, expressed or implied, is made. It is the Client's responsibility to see that all parties to the project including the Designer, Contractor, Subcontractors, etc. are made aware of this report in its entirety. The use of information contained in this report for bidding purposes should be done at the Contractor's option and risk.

7.2 ADDITIONAL SERVICES

The recommendations made in this report are based on the assumption that an adequate program of tests and observations will be made during construction to verify compliance with the recommendations contained in this report. All pertinent city or local ordinances for construction, inspection and testing should be followed during construction. We recommend the reviewing authority’s inspection and testing services should include, but not necessarily be limited to, the following:

• Observations and testing during site preparation, earthwork and structural fill placement. • Observation and testing of the zone of compacted native soil beneath foundations,

pavements and concrete slabs-on-grade. • Geotechnical Engineer consultation as may be required during construction. • Quality control testing and observation of concrete placement

© 2002 IGES, Inc. 23 R0277-014

If grading plans and specifications are produced, we also recommend the plans and specifications be reviewed by us to verify compatibility with our conclusions and recommendations. We appreciate the opportunity to be of service on this project. Should you have any questions regarding the report or wish to discuss additional services, please do not hesitate to contact us at your convenience (801) 224-8020.

© 2002 IGES, Inc. 24 R0277-014

8.0 REFERENCES CITED

Baker A. A., 1976, Geologic Map of the West Half of the Strawberry Valley Quadrangle, Utah: U.S. Geological Survey Map I-931, Scale 1:63,360.

Black, B.D., Lund, W.R., Schwartz, D.P., Gill, H.E., and Mayes, B.H., 1995, Paleoseismic Investigation

on the Salt Lake City Segment of the Wasatch Fault Zone at the South Fork Dry Creek and Dry Gulch Sites, Salt Lake County, Utah, Utah Geological Survey Special Study 92, 22p

Bromfield, C.S., Baker, A.A., and Crittenden, M.D., 1970, Geologic Map of the Heber Quadrangle

Wasatch and Summit Counties, Utah: U.S. Geological Survey Map GQ-864, scale 1:24,000. Bryant, B., 1992, Geologic and Structure Maps of the Salt Lake City 1 X 2 Quadrangle, Utah and

Wyoming: U. S. Geological Survey Map I-1997, Scale 1:125,000. Bryant, B., 1990, Geologic Map of the Salt Lake City 30’ x 60’ Quandrangle, North-Central Utah, and

Uinta County, Wyoming: U.S. Geological Survey Map I-1944, Scale 1:100,000. Earthquake Hazards Program – National Seismic Hazards Mapping Project, United States Geological

Survey, Golden, Colorado, URL: http://geohazards.cr.usgs.gov/eq/ Hecker, S., 1993, Quaternary Tectonics of Utah with Emphasis on Earthquake-Hazard Characterization:

Utah Geological Survey Bulletin 127, 157p. Hintze, L.F., 1980, Geologic Map of Utah: Utah Geological and Mineral Survey Map-A-1, scale

1:500,000. Hylland, M.D., Lowe, M., and Bishop, C.E., 1995, Engineering Geologic Map Folio, Western Wasatch

County, Utah: Utah Geological Survey OFR-319, 12 Plates, scale 1:24,000. Stokes, W.L., 1986, Geology of Utah: Utah Museum of Natural History and Utah Geological and mineral

Survey, 307 p. Aerial Photographs Reviewed for this Project:

Date Photo ID Reference

August 1, 1962 CVY-3BB-15 USDA



July 8, 1997 NAPP 10091-31 USDA

July 8, 1997 NAPP 10091-32 USDA

July 8, 1997 NAPP 10091-33 USDA

© 2002 IGES, Inc. 25 R0277-014

APPENDIX A

N

BASE MAP:HEBER CITY, UTAHU.S.G.S. 7.5 MINUTE QUADRANGLE1955

SCALE 1:50,000

0’ 2083’ 4166’

CONTOUR INTERVAL 40 feetMAP LOCATION

Project Number – 00277-014

PLATE

A-1

SITE VICINITY MAP

Approximate Site Location

Geologic/Geotechnical InvestigationSt. Moritz at Heber 12 Acre AdditionWasatch County, Utah

N

BASE MAP:Air Photo NAPP 10091-32 7/8/1997 USDA

MAP LOCATION


PLATE

A-2

SITE AERIAL PHOTOGRAPH



Potential Alluvial Fan Flooding/Debris Flow Hazard Area

N

BASE MAP:Bromfield and other, 1970

MAP LOCATION


PLATE

A-4a

SITE VICINITY GEOLOGIC MAP


SCALE 1:24,000

0’ 1000’ 2000’

CONTOUR INTERVAL 40 feet


A-4b

SITE VICINITY GEOLOGIC MAP LEGEND

PLATE



ELEVATIONEASTING

Sheet 1 of 1

T. ThompsonRubber Tire Backhoe

Plas

ticity

Inde

x

TOPSOIL - dark brown organic richclay, moist, stiff, numerous roots to12"

NORTHING

MoistureContent

NFEET

Liqu

id L

imit

Heber, Utah

N - OBSERVED UNCORRECTED BLOW COUNT

Copyright (c) 2007, IGES, INC.

STARTED:

COMPLETED:

BACKFILLED:

SAM

PLES

Bottom of Boring @ 2.5 Feet

- refusal at 2.5'

Volcanic TUFF- light brown to white,highly weathered, moderately toclosely fractured, friable tomoderately strong

IGES Rep:Rig Type:Boring Type:

102030405060708090

NOTES:

- ESTIMATED

DA

TE

- 2" O.D./1.38" I.D. SPLIT SPOON SAMPLER- 3.25" O.D./2.42" I.D. U SAMPLER- 3" O.D. THIN-WALLED SHELBY SAMPLER- GRAB SAMPLE- Modified California Sampler

LiquidLimit

BORING NO:

PlasticLimit

Perc

ent m

inus

200

SPT BLOW COUNT

9/12/02

9/12/02

9/12/02

GR

APH

ICA

L LO

G

TP- 9

Moisture Contentand

Atterberg Limits

LOG

OF

BO

RIN

G (A

) 27

7-01

4.G

PJ I

GES

.GD

T 3

/27/

07

FR - FIELD REFUSAL

UN

IFIE

D S

OIL

CLA

SSIF

ICA

TIO

N

Moi

stur

e C

onte

nt %

- MEASURED

N*

Project Number 00277-014

MET

ERS

DEPTH

MATERIAL DESCRIPTION

LOCATION

WA

TER

LEV

EL

* N - UNCORRECTED, EQUIVALENT SPT BLOW COUNT

WATER LEVEL

0

1

2

3

Dry

Den

sity

(pcf

)

SAMPLE TYPE

102030405060708090

Plate

A - 5

0

5

10

MoistureContent


Sheet 1 of 1

EASTING ELEVATION



102030405060708090

FEET

66

Heber, Utah

Liqu

id L

imit

N

Plas

ticity

Inde

x

Bottom of Boring @ 4 Feet

CH 16.3

Volcanic TUFF- light brown to white,highly weathered, moderately toclosely fractured, friable to weak

Fat CLAY - brown, stiff, moist,frequent sand, gravel and cobbles upto 6"

TOPSOIL - dark brown organic richclay, stiff, moist, numerous roots intop 12"

45


NOTES:

- ESTIMATED

STARTED:

COMPLETED:

BACKFILLED:

SAM

PLES


LiquidLimit

Moisture Contentand

Atterberg Limits

PlasticLimit

Moi

stur

e C

onte

nt %

BORING NO:

SPT BLOW COUNT

9/12/02

9/12/02

9/12/02

NORTHING

- MEASUREDLOG

OF

BO

RIN

G (A

) 27

7-01

4.G

PJ I

GES

.GD

T 3

/27/

07

FR - FIELD REFUSAL

UN

IFIE

D S

OIL

CLA

SSIF

ICA

TIO

N

DA

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WA

TER

LEV

EL

N*


Perc

ent m

inus

200

TP- 10


MET

ERS

LOCATION

GR

APH

ICA

L LO

G

Dry

Den

sity

(pcf

)

1020304050607080900

1

2

3


Plate

A - 6

0

5

10

WATER LEVEL

DEPTH

SAMPLE TYPE

Sheet 1 of 1


N

EASTING ELEVATION


GR

APH

ICA

L LO

GMoistureContent


Plas

ticity

Inde

x

IGES Rep:Rig Type:Boring Type:Heber, Utah

Liqu

id L

imit

FEET

STARTED:

COMPLETED:

BACKFILLED:

SAM

PLES


Volcaniclastic CONGLOMERATE-brown to light brown, completelyweathered, closely to moderatelyfractured, friable, fine to coarse sandand gravel. cobbles and boulders upto24", difficult to rip with backhoe

TOPSOIL - dark brown organic richclay, stiff, moist, numerous roots intop 12"

6.4

102030405060708090

NOTES:

- ESTIMATED

DA

TE


LiquidLimit

BORING NO:

PlasticLimit

Perc

ent m

inus

200

SPT BLOW COUNT

NORTHING

Moisture Contentand

Atterberg Limits

LOG

OF

BO

RIN

G (A

) 27

7-01

4.G

PJ I

GES

.GD

T 3

/27/

07

FR - FIELD REFUSAL

UN

IFIE

D S

OIL

CLA

SSIF

ICA

TIO

N

Moi

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e C

onte

nt %

TP- 11

- MEASURED

N*


WA

TER

LEV

EL


9/12/02

9/12/02

9/12/02

LOCATIONDEPTH

MET

ERS

SAMPLE TYPE


0

1

2

3

Dry

Den

sity

(pcf

)

102030405060708090

WATER LEVEL

Plate

A - 7

0

5

10

102030405060708090

EASTING ELEVATION




TOPSOIL - dark brown organic richclay, stiff, moist, numerous roots to12", frequent cobbles up to 12"

N

Sheet 1 of 1

Plas

ticity

Inde

xLi

quid

Lim

it


- refusal at 7.5'

Volcaniclastic CONGLOMERATE-completely weathered, moderatelyfractured, friable, frequent cobblesand boulders up to 24", difficult torip with backhoe

Sandy GRAVEL - brown, very dense,moist, fine to coarse sand andgravel, frequent cobbles andboulders up to 24"

SILT - brown, very stiff, moist,frequent fine to coarse sand andgravel

Poorly Graded GRAVEL wit sand -brown, very dense, moist, fine tocoarse sand and gravel

Poorly Graded GRAVEL with silt andsand - brown, very dense, moist, fineto coarse sand and gravel

- ESTIMATED

STARTED:

COMPLETED:

BACKFILLED:

NOTES:

SAM

PLES

GP

ML

GP

GP-GM

SPT BLOW COUNT

LiquidLimit

Moisture Contentand

Atterberg Limits

PlasticLimit

DA

TE

Moi

stur

e C

onte

nt %

9/12/02

9/12/02

9/12/02

TP- 12Heber, Utah

WA

TER

LEV

EL

FEET

- MEASUREDLOG

OF

BO

RIN

G (A

) 27

7-01

4.G

PJ I

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.GD

T 3

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07

FR - FIELD REFUSAL

UN

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D S

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CLA

SSIF

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TIO

N


N*


Perc

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200

BORING NO:

GR

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ICA

L LO

G

NORTHING


MoistureContent

MET

ERS

A - 8

Dry

Den

sity

(pcf

)

1020304050607080900

1

2

3

LOCATION

Plate

0

5

10

WATER LEVEL

DEPTH

SAMPLE TYPE




Sheet 1 of 1

EASTING ELEVATION



102030405060708090

MoistureContent


Heber, Utah

Liqu

id L

imit

N

Plas

ticity

Inde

x

6.6100.4 41.2

SM

GM


Silty GRAVEL with sand - brown,very dense, moist, fine to coarsesand and gravel, frequent cobblesand boulders up to 24", some coarsebedding 6" to 2' thick

Silty SAND - brown, stiff, moist,frequent fine to coarse sand andgravel

TOPSOIL - dark brown organic richsilt, stiff, slightly moist, numerousroots to 12"

NOTES:

- ESTIMATED

FEET

STARTED:

COMPLETED:

BACKFILLED:

SAM

PLES


LiquidLimit

Moisture Contentand

Atterberg Limits

PlasticLimit

Moi

stur

e C

onte

nt %

BORING NO:

SPT BLOW COUNT

9/12/02

9/12/02

9/12/02

TP- 13

NORTHINGW

ATE

R L

EVEL

- MEASUREDLOG

OF

BO

RIN

G (A

) 27

7-01

4.G

PJ I

GES

.GD

T 3

/27/

07

FR - FIELD REFUSAL

UN

IFIE

D S

OIL

CLA

SSIF

ICA

TIO

N

DA

TE

N*


Perc

ent m

inus

200


MET

ERS

LOCATION

GR

APH

ICA

L LO

G

Dry

Den

sity

(pcf

)

102030405060708090MATERIAL DESCRIPTION

Plate

A - 9

0

5

10

WATER LEVEL

DEPTH

SAMPLE TYPE

0

1

2

3

102030405060708090

NOTES:

- ESTIMATED

Liqu

id L

imit

48



Sheet 1 of 1

EASTING ELEVATION



- bouldery

Silty SAND - light brown, very stiff,moist, numerous white layers andstringers from 4 to 6', possibly withsand, frequent fine to coarse sandand gravel, occasional cobbles andboulders up to 24"

Lean CLAY - brown, very stiff, moist,fractured into cubes 0.5 to 2" wide

TOPSOIL - dark brown organic richclay, numerous roots in top 2'

29

85.5

35 10SM

N

SAM

PLES

41.0

CL

13.1

12.3

8.4

STARTED:

COMPLETED:

BACKFILLED:

Dry

Den

sity

(pcf

)

LiquidLimit

Moisture Contentand

Atterberg Limits

PlasticLimit


9/12/02

9/12/02

9/12/02

DA

TE TP- 14

Plas

ticity

Inde

x

SPT BLOW COUNT

LOG

OF

BO

RIN

G (A

) 27

7-01

4.G

PJ I

GES

.GD

T 3

/27/

07

FR - FIELD REFUSAL

UN

IFIE

D S

OIL

CLA

SSIF

ICA

TIO

N

- MEASURED

N*


Perc

ent m

inus

200

BORING NO:

Moi

stur

e C

onte

nt %

WA

TER

LEV

EL

MET

ERS

NORTHING

MoistureContent


FEET

Heber, Utah

GR

APH

ICA

L LO

G

A - 10

Plate


DEPTH

0

5

10

SAMPLE TYPE

0

1

2

3

MATERIAL DESCRIPTION102030405060708090

LOCATION

WATER LEVEL

Not Assessed Probable Possible Unlikely

XXXXXX

XX

XX

XX

XXXXXXX

XX

XX

XXX

X* Hazard Rating :

Possible - hazard may exist, but the evidence is equivocal, based only on theoretical studies, or was not observed and furthes study is necessary as notedUnlikely - no evidence was found to indicate that the hazard is present, hazard not known or suspected to be present

Further Study :

Earthquake

E - geotechnical/engineering, H - hydrologic, A - Avalanche, G - Additional detailed geologic hazard study out of the scope of this study

OrganicPipingNon-Engineered Fill

Avalanche

Collapsible

Debris Flow

Slope StabilityFlooding (Including Seiche)

Active Sand Dune

Table 2

HazardHazard Rating*

SUMMARY OF GEOLOGIC HAZARDSSt. Moritz 12-Acre Addition Heber, Utah

Further Study Recommended**


Mine SubsidenceShallow Bedrock

Ground ShakingSurface FaultingTectonic SubsidenceLiquefaction

Expansive

Rock FallLandslide

Soluble

Slope Failure

Erosion

Shallow GroundwaterFlooding

Problem Soils

StreamsAlluvial FansLakesDam Failure

Not assessed - report does not consider this hazard and no inference is made as to the presence or absence of the hazard at the siteProbable -Evidence is strong that the hazard exists and mitigation measures should be taken

Canals/DitchesRadon

PlateA-12

APPENDIX B

CH

LL(%)

100

50

40

30

20

0 20 40 80

10

4.0

0

60

60

1.0

PL(%)

CL

ML MH

452910

Fat CLAY (CH)

Silty SAND (SM)

CL-ML

B - 1PlateSaint Moritz at Heber 12 acre addition

Heber, UtahProject Number: 00277-014B

_ATT

ERB

ERG

- (U

SCS)

277

-014

.GPJ

IG

ES.G

DT

3/2

7/07

Lean CLAY (CL)TP- 14

ATTERBERG LIMITS' RESULTS

PI(%)

211925

664835

Classification

TP- 14 1.0

Sample Location Depth(ft)

LIQUID LIMIT (%)

PLA

STIC

ITY

IND

EX (%

)

TP- 10

60

TP- 11

fine

HYDROMETER

39.686101.6 0.204

6

40

CuLL

3.505

75

0.0010.010.1110100

100

95

90

30

80

70

65

60

55

50

45

35

25

20

15

10

5

0

85

Volcaniclastic CONGLOMERATE

PL

coarse

D30

16

GRAIN SIZE DISTRIBUTION

1

COBBLES GRAVEL SAND

1.52

D60

PER

CEN

T FI

NER

BY

WEI

GH

T

GRAIN SIZE (mm)

68.7

B - 2PlateSaint Moritz at Heber 12 acre addition

Heber, UtahProject Number: 00277-014B

_GSD

277

-014

.GPJ

IG

ES.G

DT

3/2

7/07

4

194.73

24.9

3/81/23/4 100

TP- 11

9.0

50

Classification9.0

6.4

3014

Sample Loctaion Depth

40

Sample Location Depth PI

2001.5

medium

6 10U.S. SIEVE OPENING IN INCHES

Cc

2

D10

4

D100

SILT OR CLAY

83 3

%Gravel %Sand %Silt

140

fine coarse

20

U.S. SIEVE NUMBERS

%Clay

B_S

WEL

L/C

OLL

APS

E 2

77-0

14.G

PJ I

GES

.GD

T 3

/27/

070

5

10

20

Saint Moritz at Heber 12 acre addition

Heber, UtahProject Number: 00277-014

Plate

100 1,000 10,000 105

B - 3

15

InundationLoad (psf)

20002000

1-D SWELL/COLLAPSE TEST

2.06.0

EFFECTIVE CONSOLIDATION STRESS (psf)

VER

TIC

AL

STR

AIN

(%)

Sample Location MC(%)

Depth(ft)

Swell(%)

Collapse(%)

1.773.85

85100

Silty SAND (SM) 13

Classification

7TP- 13TP- 14

(pcf)Silty SAND (SM)

85

80

75

90

120

95

100

105

115

125

130

CorrectedOptimum

WaterContent

135

0 10 20 30 40

110

Plate

100

80

60

40

20

00.10 0.20

B_C

OM

PAC

TIO

N S

PLIT

277

-014

.GPJ

IG

ES.G

DT

3/2

7/07

RelativeCompaction

Surcharge

% StandardCBR

50

4.10

100

111.9Dry

Density

PENETRATION (in)

STR

ESS

ON

PIS

TON

(psi

)

(%)

(%)

0.00

(pcf)

B - 4

Swell 0.17

0.500.400.30

(psf)

TP- 13 2.0 ft.

Saint Moritz at Heber 12 acre addition

Heber, UtahProject Number: 00277-014

Curves of 100% Saturation for

Specific Gravity Equal to:

PercentPassing# 200Sieve

Silty SAND (SM)

ATTERBERG LIMITS

ASTM D698 Method B

PercentPassing

# 4Sieve

COMPACTION AND CBR TEST

PIPLLL

TEST RESULTS111.8

15.6Test Method

MaximumDry Density

WATER CONTENT (%)

2.60, 2.70, 2.80

Source of MaterialMaterial Description

(%)

(pcf)

(%)

(%)

(pcf)

CorrectedMaximum

DryDensity

PercentRock

OptimumWater

Content

DR

Y D

ENSI

TY (p

cf)

Poin

t No.

Dep

th (f

t)G

rave

l

>#4

Sand

Silt

and

Cla

y

<#20

0Li

quid

Lim

itPl

astic

ity

Inde

x

Compression Ratio

Recompression Ratio

Over Consolidation

Ratio

Max

imum

D

ry D

ensi

ty

(pcf

)

A

STM

D-6

98

Met

hod

B

Opt

imum

M

oist

ure

(%)

AST

M

D

-155

7

TP-1

01

16.3

6645

Fat C

LAY

(CH

)

TP-1

19

5.9

68.7

24.9

6.4

(765

0,7.

9,20

)V

olca

nicl

astic

CO

NG

LOM

ERA

TE

TP-1

31

Silty

SA

ND

(SM

)2

6.6

100.

441

.20.

111

0.00

910

.03.

8511

1.8

15.6

4.1

Silty

SA

ND

(SM

)

TP-1

41

8.4

4829

Lean

CLA

Y (C

L)4

12.3

3510

Silty

SA

ND

(SM

)6

13.1

85.5

41.0

0.13

20.

010

6.0

0.21

Silty

SA

ND

(SM

)

Proj

ect N

ame:

St.

Mor

itz a

t Heb

er 1

2-ac

re a

dditi

onPr

ojec

t Num

ber:

002

77-0

14H

eber

, Uta

h

SUM

MA

RY

OF

LA

BO

RA

TO

RY

TE

ST R

ESU

LT

S T

AB

LE

PRO

CTO

R

CB

R

(%)

GR

AD

ATI

ON

(%)

UN

IFIE

D S

OIL

S C

LASS

IFIC

ATI

ON

CH

EMIC

AL

TEST

S (R

eses

tivity

(ohm

-cm

), PH

, Sol

uabl

e Su

lfate

(p

pm))

CO

NSO

LID

ATI

ON

ATT

ERB

ERG

LIM

ITS

Collapse (%)

Solubility (%)

SAM

PLE

LOC

ATI

ON

NA

TUR

AL

MO

ISTU

RE

CO

NTE

NT

(%)

NA

TUR

AL

DR

Y

DEN

SITY

(p

cf)

PLA

TE B-5

Documents

Geologic/Geotechnical Investigation St. Moritz at Heber 12