3-260501 Juniper Canyon Recreation Area Ph 3 Geotechnical Study.pdf

G E O T E C H N I C A L E N G I N E E R I N G S T U D Y

Juniper Canyon Trailhead Phase 3

Juniper Trail Drive and Thorley Drive

Herriman, Utah

CMT PROJECT NO. 24887

FOR:

G. Brown Design, Inc.

678 Easy Vine Street, Suite 10 Murray, Utah 84107

August 25, 2025

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WWW.CMTTECHNICALSERVICES.COM

CIVIL ENGINEERING | GEOTECHNICAL ENGINEERING | ENVIRONMENTAL | SURVEYING | MATERIALS TESTING |GEOLOGY | SPECIAL INSPECTIONS | CONSTRUCTION

MANAGEMENT | INORGANIC CHEMISTRY | SPECIALTY LABS

8/25/25

August 25, 2025

Mr. Joseph Wing, PLA G. Brown Design, Inc.

678 East Vine Street Murray, Utah 84107

Subject: Geotechnical Engineering Study Juniper Canyon Trailhead Phase 3 Juniper Trail Drive and Thorley Drive Herriman, Utah CMT Project Number: 24887

Mr. Wing:

CMT Technical Services (CMT) submits herewith this geotechnical engineering study report for the subject site. This report contains the results of our findings and an engineering interpretation of the results with respect to the available project characteristics. It also contains recommendations to aid in the design and construction of the earth related phases of this project.

On July 23, 2025, a CMT staff professional was on-site and observed the drilling of 2 bore holes extending to depths of approximately 11.5 to 16.5 feet below the existing ground surface. Samples of the subsurface soils were obtained from within the bore holes, as well as a bulk sample of near surface soil, during the field operations and subsequently transported to our laboratory for further observation and testing of select samples.

Conventional isolated and/or continuous footings may be utilized to support the proposed structures, and pavements may be supported on the prepared native subgrade soils, provided the recommendations in this report are followed. This report presents detailed discussions of design and construction criteria for this site.

We appreciate the opportunity to work with you at this stage of the project. CMT offers a full range of Geotechnical Engineering, Geological, Material Testing, Special Inspection services, and Phase I and II Environmental Site Assessments. With offices throughout Utah, Idaho, Arizona, Colorado and Texas, our staff is capable of efficiently serving your project needs. If we can be of further assistance or if you have any questions regarding this project, please do not hesitate to contact us at 801-590-0394.

Sincerely, CMT Technical Services Reviewed by:

Jeffrey J. Egbert, P.E., LEED A.P., M. ASCE Andrew M. Harris, P.E.

Senior Geotechnical Engineer Geotechnical Division Manager

TABLE OF CONTENTS

1.0 INTRODUCTION

1.1 General

1.2 Objectives, Scope and Authorization

1.3 Description of Proposed Construction

1.4 Executive Summary

2.0 FIELD EXPLORATION

3.0 LABORATORY TESTING

3.1 General

3.2 Collapse-Consolidation Testing

3.4 Moisture Density Relationship (Proctor) Testing

3.3 California Bearing Ratio Testing

4.0 GEOLOGIC & SEISMIC CONDITIONS

4.1 Geologic Setting

4.2 Faulting

4.3 Seismicity

4.3.1 Site Class

4.3.2 Ground Motions

4.3.3 Liquefaction

4.4 Other Geologic Hazards

5.0 SITE CONDITIONS

5.1 Surface Conditions

5.2 Subsurface Soils

5.3 Groundwater

5.4 Site Subsurface Variations

6.0 SITE PREPARATION AND GRADING

6.1 General

6.2 Temporary Excavations

6.3 Fill Material

6.4 Fill Placement and Compaction

6.5 Utility Trenches

6.6 Stabilization

7.0 FOUNDATION RECOMMENDATIONS

7.1 Continuous/Isolated Footings

7.2 Installation

7.3 Estimated Settlement

7.4 Lateral Resistance

8.0 LATERAL EARTH PRESSURES

9.0 FLOOR SLABS

10.0 DRAINAGE RECOMMENDATIONS

11.0 PAVEMENTS

12.0 QUALITY CONTROL

12.1 Field Observations

12.2 Fill Compaction

12.3 Excavations

13.0 LIMITATIONS

APPENDIX

Figure 1: Site Map Figures 2&3: Bore Hole Logs Figure 4: Key to Symbols

Geotechnical Engineering Study Page 1 Juniper Canyon Trailhead Phase 3, Herriman, Utah CMT Project No. 24887

1.0 INTRODUCTION

1.1 General

CMT Technical Services (CMT) was retained to conduct a geotechnical subsurface study for the proposed Juniper Canyon Trailhead Phase 3 site improvements. The site is situated on north side of the intersection of Juniper Trail Drive and Thorley Drive in Herriman, Utah, as shown in Exhibit 1 - Vicinity Map below.

EXHIBIT 1 – VICINITY MAP

1.2 Objectives, Scope and Authorization

The objectives and scope of our study were planned in discussions between Mr. Joseph Wing, PLA of G. Brown Design, Inc., and Mr. Andrew Harris of CMT. In general, the objectives of this study were to define and evaluate the subsurface soil and groundwater conditions at the site, and provide appropriate foundation, earthwork, pavement and seismic recommendations to be utilized in the design and construction of the proposed development.

In accomplishing these objectives, our scope of work has included performing field exploration, which consisted of the drilling/logging/sampling of 2 bore holes, collecting a bulk sample of near surface soil, performing laboratory testing on representative samples of the subsurface soils collected in the bore holes and the bulk

Geotechnical Engineering Study Page 2 sample, and conducting an office program, which consisted of correlating available data, performing engineering analyses, and preparing this summary report. This scope of work was authorized by returning a signed copy of our proposal dated April 18, 2025.

1.3 Description of Proposed Construction

We understand that the proposed construction consists of a pavilion, a restroom building, a kiosk, and an asphalt paved cul-de-sac and parking lot. We project that maximum structural loads will be on the order of 4,000 pounds per linear foot for walls, 40,000 pounds for columns, and a uniform 100 pounds per square foot for floor slabs. If the structural loading conditions are different than we have projected, please notify us so that any appropriate modifications to our conclusions and recommendations contained herein can be made.

We project that the pavement areas will be surfaced with asphalt. Traffic is projected to consist of mostly automobiles and light trucks, a weekly garbage truck, and an occasional fire truck.

Site development will require some earthwork in the form of minor cutting and filling. A site grading plan was not available at the time of this report, but we project that maximum cuts and fills may be on the order of 3 to 4 feet. If deeper cuts or fills are planned, CMT should be notified to provide additional recommendations, if needed.

1.4 Executive Summary

The most significant geotechnical aspects regarding site development include the following:

1. Past aerial photos indicate that there has likely been some grading of the site in conjunction with development of adjacent parcels therefore fills soils could potentially be encountered which would be considered undocumented/nonengineered.

2. Natural soils encountered predominately consisted of SILT (ML) with varying amounts of sand, and occasionally CLAY (CL), extending to the maximum depths explored approximately 11.5 to 16.5 feet below the existing ground surface.

3. Groundwater was not encountered to the maximum depth explored.

4. Foundations and at grade slabs may be constructed on suitable undisturbed natural soil or on structural/engineered fill which extends to undisturbed natural soil.

A CMT geotechnical engineer or their representative must assess that topsoil, undocumented fills (if encountered), debris, disturbed or unsuitable soils have been removed and that suitable soils have been encountered prior to placing site grading fills, footings, slabs, and pavements. In the following sections, detailed discussions pertaining to the site are provided, including subsurface descriptions, geologic setting, seismicity, earthwork, foundations, lateral resistance, lateral pressure, floor slabs, and pavements.

Geotechnical Engineering Study Page 3

2.0 FIELD EXPLORATION

To define and evaluate the subsurface soil and groundwater conditions, 2 bore holes were drilled at the site to depths of approximately 11.5 to 16.5 feet below the existing ground surface. The approximate locations of the bore holes are shown on Figure 1, Site Plan, included in the Appendix. The bore holes were logged and sampled by an experienced member of our geotechnical staff.

Samples of the subsurface soils encountered in the bore holes were collected at varying depths through the hollow stem drill augers. Relatively undisturbed samples were obtained by hydraulically pushing a 3-inch diameter (Shelby) tube or driving a split-spoon sampler with 2.5-inch outside diameter rings/liners into the undisturbed soil below the drill augers. Disturbed samples were collected utilizing a standard split spoon sampler that was driven 18 inches into the soil below the drill augers using a 140-pound hammer free-falling a distance of 30 inches. The number of hammer blows needed for each 6-inch interval was recorded. The sum of the hammer blows for the final 12 inches of penetration is known as a standard penetration test and this ‘blow count’ was recorded on the bore hole logs. The blow count provides an approximation of the relative density of granular soils, but only a limited indication of the relative consistency of silt/clay soils because the consistency of these soils is significantly influenced by the moisture content.

A bulk sample of the near surface soil was also collected for laboratory testing to aid in pavement design.

The samples of the subsurface soils retrieved from the bore holes were classified in the field based upon visual and textural examination, logged and described in general accordance with ASTM1 D-2488. These field classifications were supplemented by subsequent examination and testing of select samples in our laboratory.

Logs of the bore holes, including a description of the soil strata encountered, are presented on each individual Bore Hole Log, Figures 2 and 3, included in the Appendix. Sampling information and other pertinent data and observations are also included on the logs. In addition, a Key to Symbols defining the terms and symbols used on the logs is provided as Figure 4 in the Appendix.

3.0 LABORATORY TESTING

3.1 General

Selected samples of the subsurface soils were subjected to various laboratory tests to assess the following pertinent engineering properties:

1. Moisture Content, ASTM D-2216, Percent moisture representative of field conditions

2. Dry Density, ASTM D-2937, Dry unit weight representing field conditions

3. Atterberg Limits, ASTM D-4318, Plasticity and workability

4. Gradation Analysis, ASTM D-1140/C-117, Grain Size Analysis

5. One Dimensional Consolidation, ASTM D-2435, Consolidation properties

6. Moisture-Density Relationship (Proctor) Test, ASTM D-1557, as part of the CBR test

1 American Society for Testing and Materials

Geotechnical Engineering Study Page 4

7. California Bearing Ratio (CBR), ASTM D-2937, Subgrade support properties

Laboratory test results are presented on the bore hole logs (Figures 2 and 3), in the following Lab Summary Table, and subsequent sections:

LAB SUMMARY TABLE

BORE DEPTH SOIL SAMPLE MOISTURE DRY DENSITY

HOLE (feet) CLASS TYPE CONTENT(%) (pcf) GRAV. SAND FINES LL PL PI

B-1 5 ML Rings 21 89

B-1 7.5 ML SPT 29 93 36 27 9

B-2 0 ML SPT 9 86 27 23 4

B-2 7.5 ML Shelby 30 80 87

--- 0-2 CL Bulk 3 4 7 89 29 18 11

GRADATION ATTERBERG LIMITS

3.2 Collapse-Consolidation Testing

To provide data for an analysis of potential settlement from structural loading, a one-dimensional consolidation test was performed on each of 2 representative samples of the subsurface silt/clay soils collected in the bore holes. The collapse portion of the test was performed in accordance with the following procedure:

1. Load sample at in-situ moisture content to specific axial pressure.

2. Measure and record axial deflection.

3. Saturate sample.

4. Measure and record resulting collapse.

The results of the collapse-consolidation tests are presented below:

BORE

HOLE

DEPTH

(feet)

SOIL CLASS

MOISTURE

CONTENT (%)

DRY DENSITY

(pcf)

AXIAL LOAD AT

SATURATION (psf)

COLLAPSE (-) OR

SWELL (+)

B-1 5 ML 21 89 250 0%

B-2 7.5 ML 30 80 250 0%

The results of the tests indicate that the natural silt soils have moderate compressibility characteristics under loading. Detailed results of the tests are maintained within our files and can be transmitted to you, at your request.

3.4 Moisture Density Relationship (Proctor) Testing

A bulk sample of the near surface soil was obtained and a moisture-density relationship (Proctor) test (as part of the California Bearing Ratio test) was performed on this sample. The results of the test are presented in the table on the following page:

Geotechnical Engineering Study Page 5

DEPTH

(feet)

SOIL CLASS OPTIMUM MOISTURE CONTENT (%)

MAXIMUM DRY DENSITY

(pcf)

0-2 CL 14.9 112.8

3.3 California Bearing Ratio Testing

To determine subgrade support characteristics and to provide data for design of the proposed pavements, a CBR test was performed on the bulk sample described above in Section 3.3. The results of the CBR test are presented below:

DEPTH

(feet)

SOIL

CLASS

MOISTURE CONTENT AT

COMPACTION (%)

COMPACTED DRY

DENSITY (pcf)

COMPACTION

SWELL

CBR VALUE @

0.1/0.2

2 CL 16.6 108.6 96.3 0.8 9 / 13

4.0 GEOLOGIC & SEISMIC CONDITIONS

4.1 Geologic Setting

The subject site is in the southwest portion of the Salt Lake Valley in north-central Utah and sits at an elevation ranging from approximately 5,010 to 5,045 feet above sea level. The Salt Lake Valley is a deep, sediment-filled basin that is part of the Basin and Range Physiographic Province. The valley was formed by extensional tectonic processes during the Tertiary and Quaternary geologic time periods. The valley is bordered by the Wasatch Mountain Range on the east and the Oquirrh Mountains on the west. The Salt Lake Valley is located within the Intermountain Seismic Belt, a zone of ongoing tectonism and seismic activity extending from southwestern Montana to southwestern Utah. The active (evidence of movement in the last 10,000 years) Wasatch Fault Zone is part of the Intermountain Seismic Belt and extends from southeastern Idaho to central Utah along the western base of the Wasatch Mountain Range.

Much of northwestern Utah, including the Salt Lake Valley, was also previously covered by the Pleistocene age Lake Bonneville. The Great Salt Lake, located to the northwest of the valley, is a remnant of this ancient freshwater lake. Lake Bonneville reached a high-stand elevation of approximately 5,160 to 5,200 feet above sea level at between 18,500 and 17,400 years ago. Approximately 17,400 years ago, the lake breached its basin in southeastern Idaho and dropped by almost 300 feet relatively fast as water drained into the Snake River.

Following this catastrophic release, the lake level continued to drop slowly over time, primarily driven by drier climatic conditions until reaching the current level of the Great Salt Lake to the northwest. Shoreline terraces formed at the high-stand elevation of the lake and several subsequent lower lake levels are visible in places on the mountain slopes surrounding the valley. Much of the sediment within the Salt Lake Valley was deposited as lacustrine sediments during both the transgressive (rise) and regressive (fall) phases of Lake Bonneville and in older, pre-Bonneville lakes that previously occupied the basin.

Geotechnical Engineering Study Page 6

The geology of the UGS Tickville Spring, Utah 7.5 Minute Quadrangle, that includes the location of the subject site, has been mapped by Biek and others2. The surficial geology at the site has been mapped as “Lacustrine sand and silt related to the Bonneville (transgressive) phase of the Bonneville lake cycle ” (Map Unit Qlsb) dated as upper Pleistocene, and “Modern alluvial-fan deposits” (map unit Qaf1) dated as Holocene. Unit Qlsb is described in the referenced map as “Fine- to coarse-grained lacustrine sand and silt with minor gravel deposited between the Bonneville and Provo shorelines; grades downslope to finer grained Lake Bonneville deposits;

typically thick bedded and well sorted…” Unit Qaf1 is described in the referenced map as “Poorly to moderately sorted, weakly to non-stratified, clay- to boulder-size sediment deposited principally by debris flows at the mouths of small, active drainages;…generally less than 30 feet (9 m) thick.” No fill has been mapped at the site on the referenced map. Refer to Exhibit 2 - Geologic Map, shown below.

EXHIBIT 2 - GEOLOGIC MAP

2Biek, R.F., Solomon, B.J., Keith, J.D., Smith, T.W., 2021, Geologic Map of the Tickville Spring Quadrangle, Salt Lake and Utah Counties, Utah (GIS Reproduction of UGS Map 214DM [2005]). M-290DR. Utah Geological Survey. 1:24,000 scale.

SITE

Geotechnical Engineering Study Page 7

4.2 Faulting

No active surface fault traces are shown on the referenced geologic map crossing, adjacent to, or projecting toward the area of the subject site. The nearest mapped active fault is an unnamed Quaternary fault zone approximately 5.2 miles to the west.

4.3 Seismicity

4.3.1 Site Class

Utah has adopted the International Building Code (IBC) 2021, which determines the seismic hazard for a site based upon 2014 mapping of bedrock accelerations prepared by the United States Geologic Survey (USGS) and the soil site class. The USGS values are presented on maps incorporated into the IBC code and are also available based on latitude and longitude coordinates (grid points). For site class definitions, IBC 2021 Section 1613.2.2 refers to Chapter 20, Site Classification Procedure for Seismic Design, of ASCE3 7, which stipulates that the weighted average values of shear wave velocity, blow count and/or shear strength within the upper 100 feet (30 meters) be utilized to determine seismic site class.

Based on average shear wave velocity data within the upper 30 meters (VS,30) published by McDonald and Ashland4, the subject site is located within unit description Q02S, which has a log-mean VS,30 of 281 meters per second (922 feet per second). Thus, it is our opinion the site best fits Site Class D – Stiff Soil (with data), which we recommend for seismic structural design.

4.3.2 Ground Motions

The 2014 USGS mapping utilized by the IBC provides values of peak ground, short period and long period spectral accelerations for the Site Class B/C boundary and the Risk-Targeted Maximum Considered Earthquake (MCER).

This Site Class B/C boundary represents average bedrock values for the Western United States and must be corrected for local soil conditions. The table and response spectra on the following page summarize the peak ground, short period and long period accelerations for the MCER event, and incorporates appropriate soil correction factors for a Site Class D (with data) soil profile at site grid coordinates of 40.4805 degrees north latitude and -112.0025 degrees west longitude:

3 American Society of Civil Engineers 4McDonald, G.N. and Ashland, F.X., 2008, “Earthquake Site-Conditions Map for the Wasatch Front Urban Corridor, Utah,” Utah Geological Survey Special Study 125, 41 pp.

Geotechnical Engineering Study Page 8

Peak Ground Acceleration PGA = 0.477 Fpga = 1.123 PGAM = 0.536 1.000 PGAM = 0.536

SS = 1.085 Fa = 1.066 SMS = 1.157 0.667 SDS = 0.771

Fa = (N/A) SMS = (N/A) 0.667 SDS = (N/A)

S1 = 0.392 Fv = N/A SM1 = N/A 0.667 SD1 = N/A

Fv = (1.908) SM1 = (0.748) 0.667 SD1 = (0.499)

NOTES: 1. TL (seconds): 8 * Site Class D (With Data)

2. Site Class: D 4. ASCE 7-16 Requires Site-Specific Ground Motion Hazard Analysis (Since S1≥0.2

3. Have data to verify? yes sec) - OR Can Use Exception 2 (per §11.4.8) (Sa/Cs Plot Assumes R=Ie=1.0)

Ts =

Period

0.129332

0.646662

0.65

0.7

0.75

0.8

DESIGN VALUES

(g)

0.2 Seconds (Long Period

Acceleration)

1.0 Second (Long Period

Acceleration)

(no exceptions needed)

(Exception 2:)

SPECTRAL ACCELERATION

PERIOD, T

SITE CLASS B/C BOUNDARY

[mapped values] (g)

SITE

COEFFICIENT

SITE CLASS D* [adjusted for site class effects] (g)

MULTI-

PLIER

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

0 0.5 1 1.5 2 2.5 3 3.5 4

Sp ec tr al

R es po ns e A cc el er at io n, S a

(g

Period, T (seconds)

Baseline Sa (not for design)

As indicated in the above table, S1 is greater than 0.2 seconds and a site-specific ground motion hazard analysis (GMHA) is required for the site unless the Exception 2 values shown are used for seismic design. If a site-specific GMHA is desired instead of using the higher exception values for design, please contact CMT for a proposal to perform the GMHA.

4.3.3 Liquefaction

Liquefaction is defined as the condition when saturated, loose, sandy soils lose their support capabilities because of excessive pore water pressure which develops during a seismic event. Clayey soils, even if saturated, will generally not liquefy during a major seismic event.

The site is located within an area designated by the Utah Geologic Survey5 as having “Very Low” liquefaction potential. This is defined as a less than 5% probability that within a 100-year period an earthquake string enough to cause liquefaction will occur.

5 Utah Geological Survey, "Liquefaction-Potential Map for a Part of Salt Lake County, Utah," Utah Geological Survey Public Information Series 25, August 1994. https://ugspub.nr.utah.gov/publications/public_information/pi-25.pdf

Geotechnical Engineering Study Page 9

A special liquefaction study was not performed. The subsurface conditions we encountered support the mapped “very low’ liquefaction potential designation.

4.4 Other Geologic Hazards

No landslide deposits or features, including break away scarps or other features associated with lateral spreading, are mapped on or adjacent to the site. The site is not located within a known or mapped potential debris flow, stream flooding6, or rock fall hazard area.

The Utah Geological Survey hazard website classifies the Qaf1 alluvial fan as a “high priority alluvial fan” according to J.E. Fuller Hydrology and Geomorphology Inc. and states it “poses a high potential risk to existing infrastructure and/or population areas” according to the Division of Emergency Management.

5.0 SITE CONDITIONS

5.1 Surface Conditions

The site is currently vacant and the surface lightly to moderately vegetated with grasses and weeds. The site grade slopes to the north with an overall relief of approximately 45 feet. Based upon aerial photos dating back to 1993 that are readily available on the internet, it appears that some grading of the site may have occurred in conjunction with adjacent developments. The site appears to have remained relatively unchanged since 2020.

The site is bordered on the north by vacant land, on the south by Thorley Drive, and on the east and west by single family residences (see Vicinity Map in Section 1.1 above).

5.2 Subsurface Soils

Though not noted on the field bore hole logs, a relatively thin topsoil layer may be encountered where surface vegetation is denser. Considering the grading that appears to have occurred on the site in the past, loose/disturbed soils and/or undocumented/non-engineered fill soils could be encountered, which will likely vary in depth and extent if encountered, across the site.

At the locations of the bore holes, we encountered natural soils consisting of SILT (ML) with varying amounts of sand extending to the maximum depths explored of approximately 11.5 to 16.5 feet below the existing ground surface. Based upon laboratory testing the near surface bulk sample collected was Lean CLAY (CL) with trace to some sand and gravel.

The silt/clay soils were slightly moist to moist, light brown to grayish brown in color, and predominately of medium stiff to stiff consistency based upon the blow counts. The silt soils exhibited moderate over consolidation and moderate compressibility characteristics in laboratory testing.

6https://msc.fema.gov/arcgis/rest/directories/arcgisjobs/nfhl_print/mscprintb_gpserver/jdb339ef8f49a4d289701830f82ca49af/scra tch/FIRMETTE_3d3dfdd4-e54a-47dc-af37-f616ae3207ed.pdf

Geotechnical Engineering Study Page 10

For a more descriptive interpretation of subsurface conditions, please refer to the bore hole logs, Figures 2 and 3, which graphically represent the subsurface conditions encountered. The lines designating the interface between soil types on the logs generally represent approximate boundaries; in situ, the transition between soil types may be gradual.

5.3 Groundwater

Groundwater was not encountered at the time of our field explorations to the maximum depth explored of approximately 16.5 feet below the existing ground surface. We do not anticipate that groundwater will be encountered during construction.

Groundwater levels can fluctuate seasonally. Numerous other factors such as heavy precipitation, irrigation of neighboring land, and other unforeseen factors, may also influence ground water elevations at the site. The detailed evaluation of these and other factors, which may be responsible for ground water fluctuations and the magnitude of potential fluctuations, is beyond the scope of this study.

5.4 Site Subsurface Variations

Based on the results of the subsurface explorations and our experience, variations in the continuity and nature of subsurface conditions should be anticipated. Due to the heterogeneous characteristics of natural soils, care should be taken in interpolating or extrapolating subsurface conditions between or beyond the exploratory locations.

Undocumented fill and/or topsoil could be encountered on the surface of portions of the site and will vary in extent and depth throughout the site.

6.0 SITE PREPARATION AND GRADING

6.1 General

All deleterious materials should be stripped from the site prior to commencement of construction activities.

This includes vegetation, topsoil, loose and disturbed soils, etc. When stripping and grubbing, topsoil, if encountered, should be distinguished by the apparent organic content and not solely by color.

Based upon past aerial photos readily available on the internet, undocumented fill could be encountered on the surface of the site in some areas. All undocumented fill shall be removed from beneath structures, but may remain beneath exterior flatwork and pavements, provided they are properly prepared and the owner understands that, depending on the fill thickness, the improperly compacted fill soils can consolidate/settle over time, and additional maintenance of surfaces constructed over them may be required. Outside of building footprints, proper preparation of undocumented fill and disturbed soils shall consist of removing the upper 12 inches, scarifying the exposed surface to a minimum depth of 8 inches, moisture conditioning as needed and recompacting the scarified soils in place to the requirements for structural fill specified in Section 6.4. The

Geotechnical Engineering Study Page 11 removed soils, if free of debris, organics, or other deleterious materials, may then be re-placed and compacted to the same requirements. If desired, the removed soils could also be replaced with structural fill per meeting the requirements in Section 6.3 and compacted to the same requirements as structural fill as outlined in Section

6.4. Removals should extend at least 4 feet beyond the perimeter of structures and at least 2 feet beyond the perimeter of flatwork and pavement.

Following stripping, clearing and/or grubbing, the subgrade should be observed by a CMT geotechnical engineer or their representative to assess that suitable natural soils have been exposed and any deleterious materials, loose and/or disturbed soils have been removed, prior to placing site grading fills, footings, slabs, and pavements.

Fill placed over large areas to raise overall site grades can induce settlements in the underlying natural soils. If more than 3 feet of site grading fill is anticipated over the natural ground surface, we should be notified to assess potential settlements and provide additional recommendations as needed. These recommendations may include placement of the site grading fill far in advance to allow potential settlements to occur prior to construction.

Where the ground surface slopes steeper than 5H:1V (Horizontal:Vertical), the ground should be benched prior to placing fill (following stripping and grubbing the site as discussed above) such that the fill is placed on relatively level surfaces and against vertical surfaces. We recommend maximum bench heights of 4 feet with the lowest bench cut and keyed at least 3 feet deep and 6 feet wide into the bottom of the slope.

6.2 Temporary Excavations

Excavations deeper than 8 feet are not anticipated at the site. Groundwater was not encountered within the depths explored, approximately 11.5 to 16.5 feet at the time of our field explorations and thus is not anticipated to be encountered in excavations.

The natural soils encountered at this site consisted of silt/clay. In clayey (cohesive) soils, temporary construction excavations not exceeding 4 feet in depth may be constructed with near-vertical side slopes. Temporary excavations up to 8 feet deep, above or below groundwater, may be constructed with side slopes no steeper than one-half horizontal to one vertical (0.5H:1V).

For non-plastic silt and sandy/gravelly (cohesionless) soils, temporary construction excavations not exceeding 4 feet in depth should be no steeper than one-half horizontal to one vertical (0.5H:1V). For excavations up to 8 feet and above groundwater, side slopes should be no steeper than one horizontal to one vertical (1H:1V).

Excavations encountering saturated cohesionless soils will be very difficult to maintain and will require very flat side slopes and/or shoring, bracing and dewatering.

To reduce disturbance of the natural soils during excavation, we recommend that smooth edge buckets/blades be utilized.

Geotechnical Engineering Study Page 12

All excavations must be inspected periodically by qualified personnel. If any signs of instability or excessive sloughing are noted, immediate remedial action must be initiated. All excavations should be made following OSHA safety guidelines.

6.3 Fill Material

Structural fill is defined as fill that will ultimately be subjected to structural loads imposed by footings, floor slabs, pavements, etc. Structural fill will be required as backfill over foundations and utilities, as site grading fill, and potentially as replacement fill below footings. All structural fill must be free of sod, rubbish, topsoil, frozen soil, and other deleterious materials. Following are our recommendations for the various fill types we anticipate will be used at this site:

FILL MATERIAL TYPE DESCRIPTION | RECOMMENDED SPECIFICATION

Select Structural Fill

Placed below structures, flatwork and pavement. Well-graded sand/gravel mixture, with maximum particle size of 4 inches, a minimum 70% passing 3/4-inch sieve, approximately 30% to 60% passing the No. 4 sieve, a maximum 20% passing the No. 200 sieve, and a maximum Plasticity Index of 10.

Imported Site Grading Fill

Placed over large areas to raise the site grade. Sandy to gravelly soil, with a maximum particle size of 6 inches, a minimum 70% passing 3/4-inch sieve, a maximum 50% passing No. 200 sieve, and a maximum Plasticity Index of 15.

Non-Structural Fill Placed below non-structural areas, such as landscaping. On-site soils or imported soils, with a maximum particle size of 8 inches, including silt/clay soils not containing excessive amounts of degradable/organic material (see discussion below).

Stabilization Fill Placed to stabilize soft areas prior to placing structural fill and/or site grading fill. Coarse angular gravels and cobbles 1 inch to 8 inches in size. May also use 1.5- to 2.0-inch gravel placed on stabilization fabric, such as Mirafi RS280i, or equivalent (see Section 6.6).

Natural silt/clay soils are not suitable for use as structural fill but may be used as site grading fill and non-structural fill. Note that these silt/clay soils are inherently more difficult to work with in proper moisture conditioning (they are very sensitive to changes in moisture content), requiring very close moisture control during placement and compaction. This will be very difficult, if not impossible, during wet and cold periods of the year.

All fill material should be approved by a CMT geotechnical engineer prior to placement.

6.4 Fill Placement and Compaction

The various types of compaction equipment available have their limitations as to the maximum lift thickness that can be compacted. For example, hand operated equipment is limited to lifts of about 4 inches and most “trench compactors” have a maximum, consistent compaction depth of about 6 inches. Large rollers, depending on soil and moisture conditions, can achieve compaction at 8 to 12 inches. The full thickness of each lift should

Geotechnical Engineering Study Page 13 be compacted to at least the following percentages of the maximum dry density as determined by ASTM D-1557 (or AASHTO7 T-180) in accordance with the following recommendations:

LOCATION

TOTAL FILL

THICKNESS

(FEET)

MINIMUM PERCENTAGE

OF MAXIMUM DRY

DENSITY

Beneath an area extending at least 4 feet beyond the perimeter of structures, and below flatwork and pavement (applies to structural fill and site grading fill) extending at least 2 feet beyond the perimeter

0 to 5 5 to 8

Site grading fill outside area defined above 0 to 5 5 to 8

Reworked in-situ fill Up to 20 inches 93

Utility trenches within structural areas -- 96

Roadbase and subbase - 96

Non-structural fill 0 to 5 5 to 8

Fills greater than 8 feet thick are not anticipated at the site. For best compaction results, we recommend that the moisture content for structural fill/backfill be within 2% of optimum. Field density tests should be performed on each lift as necessary to verify that proper compaction is being achieved.

6.5 Utility Trenches

For the bedding zone around the utility, we recommend utilizing sand bedding fill material that meets current APWA8 requirements.

All utility trench backfill material below structurally loaded facilities (foundations, floor slabs, flatwork, parking lots/drive areas, etc.) should be placed at the same density requirements established for structural fill in the previous section.

Most utility companies and local governments are requiring Type A-1a or A-1b (AASHTO Designation) soils (sand/gravel soils with limited fines) be used as backfill over utilities within public rights of way, and the backfill be compacted over the full depth above the bedding zone to at least 96% of the maximum dry density as determined by AASHTO T-180 (ASTM D-1557).

Where the utility does not underlie structurally loaded facilities and public rights of way, natural soils may be utilized as trench backfill above the bedding layer, provided they are properly moisture conditioned and compacted to the minimum requirements stated above in Section 6.4.

7 American Association of State Highway and Transportation Officials 8 American Public Works Association

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6.6 Stabilization

The natural silt/clay soils at this site will likely be susceptible to rutting and pumping. The likelihood of disturbance or rutting and/or pumping of the existing natural soils is a function of the moisture content, the load applied to the surface, as well as the frequency of the load. Consequently, rutting and pumping can be reduced by avoiding concentrated traffic, reducing the load applied to the surface by using lighter equipment and/or partial loads, by working in drier times of the year, or by providing a working surface for the equipment.

Rubber-tired equipment particularly, because of high pressures, promotes instability in moist/wet, soft soils.

If rutting or pumping occurs, traffic should be stopped, and the disturbed soils should be removed and replaced with stabilization material. Typically, a minimum of 18 inches of the disturbed soils must be removed to be effective. However, deeper removal is sometimes required.

To stabilize soft subgrade conditions (if encountered), a mixture of coarse, clean, angular gravels and cobbles and/or 1.5- to 2.0-inch clean gravel should be utilized. This coarse material may be placed and worked into the soft soils until firm and non-yielding, or the soft soils may be removed an additional 18 inches (minimum) and backfilled with clean stabilizing angular gravels/cobbles. A test area should be implemented to achieve a proper stabilization strategy. Often the amount of gravelly material can be reduced with the use of a geotextile fabric such as Mirafi RS280i, or equivalent. Its use will also help avoid mixing of the subgrade soils with the gravelly material. After excavating the soft/disturbed soils, the fabric should be spread across the bottom of the excavation and up the sides a minimum of 18 inches. Otherwise, it should be placed in accordance with the manufacturer’s recommendation, including proper overlaps. The gravel material can then be placed over the fabric in compacted lifts as described above.

7.0 FOUNDATION RECOMMENDATIONS

The following recommendations have been developed based on the previously described project characteristics, the subsurface conditions observed in the field and the laboratory test data, as well as common geotechnical engineering practice.

7.1 Continuous/Isolated Footings

Based on our geotechnical engineering analyses, the proposed structures may be supported upon conventional isolated and/or continuous wall foundations placed on suitable, undisturbed natural soils and/or on structural fill extending to suitable natural soils. Footings may be designed using a net bearing pressure of 1,500 psf if placed on suitable, undisturbed, natural soils or 2,000 psf if placed on a minimum 18 inches of structural fill. The allowable bearing pressure may be increased by 1/3 for temporary loads such as wind and seismic forces.

We also recommend the following:

1. Exterior footings subject to frost should be placed at least 30 inches below final grade.

2. Interior footings not subject to frost should be placed at least 12 inches below grade.

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3. Continuous footing widths should be maintained at a minimum of 18 inches.

4. Isolated footings should be a minimum of 24 inches wide.

7.2 Installation

Under no circumstances shall foundations be placed on undocumented fill, topsoil with organics, sod, rubbish, construction debris, other deleterious materials, frozen soils, or within ponded water. If unsuitable soils are encountered, they must be completely removed and replaced with properly compacted structural fill.

Deep, large roots may be encountered where trees and larger bushes are located or were previously located at the site; such large roots should be removed. The base of footing excavations should be observed by a CMT geotechnical engineer to assess that suitable bearing soils have been exposed.

All structural fill placed below footings should meet the requirements for such and should be placed and compacted in accordance with Section 6.4 above. The width of structural replacement fill below footings should be equal to the width of the footing plus 1 foot for each foot of fill thickness. For instance, if the footing width is 2 feet and the structural fill depth beneath the footing is 2 feet, the fill replacement width should be 4 feet, centered beneath the footing.

The minimum thickness of structural fill below footings should be equivalent to one-third the thickness of structural fill below any other portion of the foundations. For example, if the maximum depth of structural fill is 6 feet, all footings for the new structure should be underlain by a minimum 2 feet of structural fill.

7.3 Estimated Settlement

Foundations designed and constructed in accordance with our recommendations could experience settlement, but we anticipate that total settlements of footings founded as recommended above will not exceed 1 inch, with differential settlements on the order of 0.5 inches over a distance of 25 feet. We expect approximately 50% of the total settlement to initially take place during construction.

7.4 Lateral Resistance

Lateral loads imposed upon foundations due to wind or seismic forces may be resisted by the development of passive earth pressures and friction between the base of the footings and the supporting soils. In determining frictional resistance, a coefficient of 0.30 for natural silt/clay soils or 0.40 for select structural fill, may be utilized for design. Passive resistance provided by properly placed and compacted natural silt/clay soils above the water table may be considered equivalent to a fluid with a density of 350 pcf. A combination of passive earth resistance and friction may be utilized if the passive resistance component of the total is divided by 1.5. Note that frictional resistance is mobilized as soon as any movement occurs, while full passive pressure is typically achieved after a small amount of movement occurs (approximately 0.5% of the footing height).

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8.0 LATERAL EARTH PRESSURES

We anticipate that below-grade walls up to 4 feet high might be constructed at this site. The lateral earth pressure values given below are for a backfill material that will consist of drained natural silt/clay soils placed and compacted in accordance with the recommendations presented herein. If other soil types are used as backfill, we should be notified so that appropriate modifications to these values can be provided, as needed.

The lateral pressures imposed upon subgrade facilities will depend upon the relative rigidity and movement of the backfilled structure. Following are the recommended lateral pressure values, which also assume that the soil surface behind the wall is horizontal and that the backfill within 3 feet of the wall will be compacted with hand-operated compacting equipment. For subgrade walls less than 12 feet high, employing a seismic at-rest lateral earth pressure for design is not needed.

CONDITION STATIC (psf/ft)* SEISMIC (psf/ft)**

Active Pressure (wall is allowed to yield, i.e. move away from the soil, with a minimum 0.001H movement/rotation at the top of the wall, where “H” is the total height of the wall)

40 23

At-Rest Pressure (wall is not allowed to yield) 60 N/A

Passive Pressure (wall moves into the soil) 350 95 *Equivalent Fluid Pressure (applied at 1/3 Height of Wall)

**Equivalent Fluid Pressure (added to static and applied at 1/3 Height of Wall)

9.0 FLOOR SLABS

Properly engineered floor slabs should be established upon uniform, compacted bearing soils comprised of suitable, undisturbed uniform natural soils or on structural fill extending to suitable natural soils (similar to foundations). Under no circumstances shall floor slabs be established directly on any topsoil, undocumented fills, loose or disturbed soils, sod, rubbish, construction debris, other deleterious materials, frozen soils, or within ponded water. Floor slabs should be properly designed by a structural engineer to accommodate anticipated loads.

To facilitate curing of the concrete, we recommend that floor slabs be directly underlain by at least 4 inches of moist aggregate base or bedding material, or “free-draining” fill such as “pea” gravel or 3/4-inch to 1-inch minus, clean, gap-graded gravel. To help control normal shrinkage and stress cracking, the floor slab thickness and joint layout should be designed by a qualified engineer. Design provisions should address the following items:

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1. Adequate reinforcement for the anticipated floor loads;

2. Using smooth bar reinforcement for load transfer through interior floor joints;

3. Portland cement concrete mix design selection to minimize shrinkage concerns;

4. Joint layout and spacing in accordance with ACI9 or other local standards; and

5. Properly isolate floor slabs from foundations and other structural elements per recommendations provided by ACI 302 (Guide to Concrete Floor and Slab Construction).

10.0 DRAINAGE RECOMMENDATIONS

It is important to the long-term performance of foundations and floor slabs that water not be allowed to collect near the foundation walls and infiltrate into the underlying soils. We recommend the following:

1. All areas around each structure should be sloped to provide drainage away from the foundations. We recommend a minimum slope of 4 inches in the first 10 feet away from the structure. This slope should be maintained throughout the lifetime of the structure.

2. All roof drainage should be collected in rain gutters with downspouts designed to discharge at least 10 feet from the foundation walls or well beyond the backfill limits, whichever is greater.

3. Adequate compaction of the foundation backfill should be provided. We suggest a minimum of 90% of the maximum laboratory density as determined by ASTM D-1557. Water consolidation methods should not be used under any circumstances.

4. Landscape sprinklers should be aimed away from the foundation walls. The sprinkling systems should be designed with proper drainage and be well-maintained. Over watering should be avoided.

5. Other precautions that may become evident during construction.

11.0 PAVEMENTS

All pavement areas must be prepared as discussed above in Section 6.1. Under no circumstances shall pavements be established over topsoil, unprepared undocumented fills (if encountered), loose or disturbed soils, sod, rubbish, construction debris, other deleterious materials, frozen soils, or within ponded water.

In pavement areas, subsequent to stripping and prior to the placement of pavement materials, the exposed subgrade must be proof rolled by passing moderate-weight rubber tire-mounted construction equipment over the surface at least twice. If soft or otherwise unsuitable soils are encountered, we recommend they be removed to a minimum depth of 18 inches below the subgrade level and replaced with structural fill.

Based on the results of our laboratory testing (see Section 3.0) the natural near surface soils have a California Bearing Ratio (CBR) of 9. We anticipate the on-site silt/clay soils will exhibit poor pavement support

9 American Concrete Institute

Geotechnical Engineering Study Page 18 characteristics when saturated or nearly saturated. Based on our laboratory testing experience with similar soils, our pavement design is based upon a California Bearing Ratio (CBR) of 3 for the on-site silt/clay soils.

Given the projected traffic as discussed above in Section 1.3, the following pavement sections are recommended for the given ESAL's (18-kip equivalent single-axle loads) per day:

MATERIAL

PAVEMENT SECTION THICKNESS (inches)

PARKING AREAS

(1 ESAL per day)

DRIVE AREAS

(3 ESAL'S per day)

Asphalt 3 3 3.5 3.5

Road-Base (UTBC) 8 4 10 6

Subbase 0 6 0 6

Total Thickness 11 13 13.5 15.5

Untreated base course (UTBC), typically known as road-base, should conform to APWA specifications, or to 1.5-inch-minus UDOT specifications for A–1-a/NP, and have a minimum CBR value of 70%. Subbase should be a granular material having a minimum CBR value of 40%. Road base and subbase material should be compacted as recommended above in Section 6.4. Asphalt material generally should conform to APWA requirements, having a ½-inch maximum aggregate size, a 75-gyration Superpave mix containing no more than 15% of recycled asphalt (RAP) and a PG58-28 binder.

For dumpster pads, we recommend a pavement section consisting of 6.5 inches of Portland cement concrete and 6 inches of aggregate base over properly prepared suitable natural subgrade or site grading structural fills extending to suitable natural soils. Dumpster pads constructed overlying undocumented fills must be avoided or heavily reinforced.

12.0 QUALITY CONTROL

We recommend that CMT be retained as part of a comprehensive quality control testing and observation program. With CMT onsite we can help facilitate implementation of our recommendations and address, in a timely manner, any subsurface conditions encountered which vary from those described in this report. Without such a program CMT cannot be responsible for application of our recommendations to subsurface conditions which may vary from those described herein. This program may include, but not necessarily be limited to, the following:

12.1 Field Observations

Observations should be completed during all phases of construction such as site preparation, foundation excavation, structural fill placement and concrete placement.

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12.2 Fill Compaction

Compaction testing by CMT is required for all structural supporting fill materials. Maximum Dry Density (Modified Proctor, ASTM D-1557) tests should be requested by the contractor immediately after delivery of any fill materials. The maximum density information should then be used for field density tests on each lift as necessary to verify that the required compaction is being achieved.

12.3 Excavations

All excavation procedures and processes should be observed by a geotechnical engineer from CMT or their representative. In addition, for the recommendations in this report to be valid, all backfill and structural fill placed in trenches and all pavements should be density tested by CMT. We recommend that freshly mixed concrete be tested by CMT in accordance with ASTM designations.

13.0 LIMITATIONS

The recommendations provided herein were developed by evaluating the information obtained from the subsurface explorations and soils encountered therein. The exploration logs reflect the subsurface conditions only at the specific location at the particular time designated on the logs. Soil and ground water conditions may differ from conditions encountered at the actual exploration locations. The nature and extent of any variation in the explorations may not become evident until during the course of construction. If variations do appear, it may become necessary to re-evaluate the recommendations of this report after we have observed the variation.

Our professional services have been performed, our findings obtained, and our recommendations prepared in accordance with generally accepted geotechnical engineering principles and practices. This warranty is in lieu of all other warranties, either expressed or implied.

We…