4-25557 West Jordan 70th South Landscape - 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

70th South Landscape Project

Jordan Canal to ±900 Feet West

West Jordan, Utah

CMT PROJECT NO. 25557

FOR:

City of West Jordan 8000 South Redwood Road West Jordan, Utah 84088

January 16, 2026

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WWW.CMTTECHNICALSERVICES.COM

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

MANAGEMENT | INORGANIC CHEMISTRY | SPECIALTY LABS

1/16/26

January 16, 2026

Mr. Tyler Crawford City of West Jordan 8000 South Redwood Road West Jordan, Utah 84088

Subject: Geotechnical Engineering Study 70th South Landscape Project Jordan Canal to ±900 Feet West West Jordan, Utah CMT Project No. 25557

Mr. Crawford:

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 November 24 and 25, 2025, CMT staff professionals were on-site and observed the drilling of 6 bore holes and 3 hand auger holes extending to depths of about 5.5 to 51.5 feet below the existing ground surface. Soil samples were obtained during the field operations and subsequently transported to our laboratory for further testing and observation.

This report presents recommendations and discussions regarding the design and construction criteria for the proposed landscape improvements at 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:

William G. Turner, P.E., M. ASCE Jeffrey J. Egbert, P.E., LEED A.P., M. ASCE Senior Geotechnical Engineer Senior Geotechnical Engineer

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 Direct Shear Testing

3.3 Laboratory Vane Shear 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 BLOCK WALL STABILITY AND RECOMMENDATIONS

8.1 Stability Parameters

8.2 Stability Analysis

8.3 Verti-Block Wall Recommendations

9.0 QUALITY CONTROL

9.1 Field Observations

9.2 Fill Compaction

9.3 Excavations

10.0 LIMITATIONS

APPENDIX

Figure 1: Site Map Figures 12-13: Direct Shear Test Figures 2-4: Hand Auger Logs Figures 14-17: Verti-Block Wall Details Figures 5-10: Bore Hole Logs Stability Graphs/Input/Output Data (10 pages) Figure 11: Key to Symbols Calculations (9 pages)

Geotechnical Engineering Study Page 1 70th South Landscape Project, West Jordan, Utah CMT Project No. 25557

1.0 INTRODUCTION

1.1 General

CMT Technical Services (CMT) was retained to conduct a geotechnical subsurface study for the proposed landscape improvements along 7000 South between the Jordan Canal and about 900 feet west of the canal in West Jordan, 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 outlined in the Professional Service Request by West Jordan City in the summer of 2025. In general, the objectives of this study were to define and evaluate the subsurface soil and groundwater conditions at the site and provide appropriate block wall and earthwork recommendations to be utilized in the design and construction of the proposed landscape improvements.

In accomplishing these objectives, our scope of work has included performing field exploration, which consisted of the drilling/logging/sampling of 6 bore holes and 3 hand auger holes, performing laboratory testing on representative samples of the subsurface soils collected in the bore holes, and conducting an office program, SITE

Geotechnical Engineering Study Page 2 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 September 25, 2025.

1.3 Description of Proposed Construction

We understand that the proposed construction consists of improvements to the landscaping along 7000 South from approximately the Jordan Canal to about 850 to 900 feet west of the canal. Verti-block retaining walls will be constructed at the site to facilitate side grading for the landscape improvements as well as a monument sign.

Site development will require some earthwork in the form of minor cutting and filling. The plans provided to CMT (by Consor Engineers dated June 24, 2025) indicate that maximum cuts and fills may be on the order of 3 to 6 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. Approximately 1.5 to 2.5 feet of undocumented fill (including a root mat at the surface that is a few inches thick) blankets the site; foundations should not be placed on undocumented fill.

2. Subsurface soils encountered below the undocumented fill consisted of CLAY (CL), SILT (ML) and SAND

(SM, SC) soils extending to the maximum depth explored of 51.5 feet below the existing ground surface.

3. Groundwater was encountered and measured at depths ranging from 2.5 to 30 feet; shallow groundwater on the east end of the project will likely affect excavations and construction.

4. Liquefaction will likely occur at this site during a major earthquake, but we anticipate settlements at the ground surface will be less than 1 inch and, thus, mitigation of susceptible soils is not warranted.

5. The monument foundation may be constructed on undisturbed natural soils or on select structural/engineered fill which extends to natural soils.

CMT must assess that topsoil, undocumented fills, debris, loose/disturbed or other unsuitable soils have been removed and that undisturbed natural soils have been encountered prior to placing structural fills, 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, and Verti-block wall recommendations.

2.0 FIELD EXPLORATION

To define and evaluate the subsurface soil and groundwater conditions, 6 bore holes and 3 hand auger holes were drilled at the site to depths of approximately 5.5 to 51.5 feet below the existing ground surface. Locations of the explorations are shown on Figure 1, Site Plan, included in the Appendix. The field exploration was performed under the observation of an experienced member of our geotechnical staff.

Geotechnical Engineering Study Page 3

Samples of the subsurface soils encountered in the bore holes were collected at varying depths through the hollow stem drill augers. Relatively undisturbed samples of the subsurface soils were obtained by driving a split-spoon sampler with 2.5-inch outside diameter rings/liners into the undisturbed soils below the drill augers.

Disturbed samples were collected utilizing a standard split spoon sampler that was driven 18 inches into the soils 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.

The subsurface soils encountered in 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 explorations, including a description of the soil strata encountered, are presented on each individual log, Figures 2 through 10, 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 11 in the Appendix.

Following completion of drilling operations, the holes were backfilled with auger cuttings.

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. Direct Shear Test, ASTM D-3080, Shear strength parameters

7. Vane Shear Test, ASTM D-4648, Shear strength parameters

To provide data for an analysis of potential settlement from structural loading, a one-dimensional consolidation test was performed on a representative sample of the subsurface clay soils collected in the bore holes. Based upon data obtained from the consolidation testing, the clay soils at this site are moderately over-consolidated and moderately compressible under additional loading. Detailed results of the test are maintained within our files and can be transmitted to you, if so desired.

1 American Society for Testing and Materials

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Laboratory test results are presented on the exploration logs (Figures 2 through 10), on Figures 12 and 13, Direct Shear Test, and in the following Lab Summary Table:

LAB SUMMARY TABLE

BORE DEPTH SOIL SAMPLE MOISTURE DRY DENSITY COLLAPSE (-)/

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

HA-1 2.5 CL Bag 25 0 9 91

10 CL Bag 28 0 6 94 27 19 8

HA-2 2.5 CL Bag 12 2 20 78

HA-3 2.5 CL Bag 13 0 9 91 29 19 10

6.5 SM Bag 8 0 68 32

B-1 5 SM SPT 20 7 76 17

10 CL Rings 21 0 45 55

20 CH SPT 36 0 1 99 50 23 27

35 CL SPT 25 0 2 98 39 19 20

B-2 7.5 CL Rings 28 4 8 88

25 CL Rings 20 106 0 42 58

30 CH SPT 33 53 21 32

B-3 5 CL SPT 29 0 3 97 39 23 16

10 CL Rings 34 88 0 2 98

B-4 5 CL Rings 11 109 2 18 80 +0.2%

35 CL SPT 32 0 5 95 33 19 14

B-5 5 CL SPT 11 0 18 82 27 19 8

7.5 CL Rings 10 88 0 25 75

15 CL Rings 31 92 0 1 99

25 CL SPT 33 0 2 98 40 20 20

35 ML SPT 36 0 34 66 NP NP

45 ML SPT 24 0 30 70 17 16 1

B-6 5 GC SPT 10 37 32 31

15 CL Rings 32 91 2 3 95

GRADATION ATTERBERG LIMITS

3.2 Direct Shear Testing

A direct shear test was performed on two representative samples of the subsurface clay soils. Each sample was evenly loaded/consolidated within the test ring and saturated immediately after the load was applied; after consolidation was completed, the sample was sheared horizontally while measuring the shearing force and the horizontal and vertical deformations of the sample. This process was repeated twice while increasing the normal load imposed on the sample. Detailed results of the test are shown on the attached Figures 12 and 13, Direct Shear Test; a summary of the testing is presented below:

Geotechnical Engineering Study Page 5

BORE

HOLE

DEPTH

(feet)

SOIL

CLASS

SAMPLE

TYPE

INTERNAL FRICTION ANGLE

(degrees)

APPARENT COHESION

(psf)

B-1 10 CL Ring 30.9 456

B-2 7.5 CL Ring 25.4 446

3.3 Laboratory Vane Shear Testing

To determine the undrained shear strength of the soils encountered at the site, laboratory vane shear tests were performed. The results of the tests are presented below:

BORE

HOLE

DEPTH

(feet)

SOIL

CLASS

MOISTURE CONTENT

DRY DENSITY

(pcf)

ULTIMATE SHEAR STRENGTH

(psf)

B-3 10 CL 34 88 3,740

B-5 15 CL 31 92 5,925

4.0 GEOLOGIC & SEISMIC CONDITIONS

4.1 Geologic Setting

The subject site is located in the central portion of the Salt Lake Valley in north-central Utah. The site sits at an elevation of approximately 4,315 to 4,340 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 and 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 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 5,092 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. 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.

Geotechnical Engineering Study Page 6

The geology of the USGS Midvale, Utah 7.5 Minute Quadrangle, that includes the location of the subject site, has been mapped by McKean2. The surficial geology at the location of the subject site and adjacent properties is mapped as “Fine-grained lacustrine deposits of the Bonneville lake cycle” (Map Unit Qlf) dated to be late Pleistocene. Unit Qlf is described in the mapping as “Transgressive and regressive, deep-water sediments;

brown, dark-brown, grayish-brown, and gray calcareous, laminated silt, clayey silt, and sandy silt; commonly contains isolated pebbles, cobbles, and thin lenses of sand and gravel that were deposited by ice-rafting (dropstones) and turbidity flows.” No fill has been mapped at the location of the site on the geologic map. Refer to Exhibit 2 - Geologic Map, shown below.

Qlf

EXHIBIT 2 - GEOLOGIC MAP

4.2 Faulting

No surface fault traces are shown on the referenced geologic map crossing or projecting toward the subject site.

The nearest mapped active (Holocene-age) fault trace is the Granger section of the West Valley fault zone located about 3 miles north-northwest of the site. Seismic design issues are addressed in Section 4.3 below.

2 McKean, A., 2024, Interim Geologic Map of the Midvale Quadrangle, Salt Lake County, Utah; Utah Geological Survey Open File Report 761, Scale 1:24,000.

SITE

Geotechnical Engineering Study Page 7

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 290 meters per second (951 feet per second, which fits Site Class D). In addition, one data point from the McDonald and Ashland publication is located about 1,150 feet northwest of the site with a VS,30 of 278 meters per second (912 feet per second, which also fits Site Class D). 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 at site grid coordinates of 40.6238 degrees north latitude and -111.9250 degrees west longitude. 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:

3 American Society of Civil Engineers 4 McDonald, 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 = 0.597 Fpga = 1.100 PGAM = 0.657 1.000 PGAM = 0.657

SS = 1.342 Fa = 1.000 SMS = 1.342 0.667 SDS = 0.895

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

S1 = 0.470 Fv = N/A SM1 = N/A 0.667 SD1 = N/A

Fv = (1.830) SM1 = (0.860) 0.667 SD1 = (0.573)

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

0.128182

0.640909

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

0.2

0.4

0.6

0.8

1.2

0 0.5 1 1.5 2 2.5 3 3.5 4

Sp e ct ra l R e sp o n se

A cc e le ra ti o n

, S a

(g

Period, T (seconds)

Baseline Sa (not for design)

Sa/Cs (Adjusted for Exception 2)

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

The site is located within an area designated by the Utah Geologic Survey5 as having “Moderate” liquefaction potential. 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.

Subsurface soils encountered below groundwater (encountered in bore holes B-1, B-2, B-4 and B-5) consisted of clayey soils with plasticity indices greater than 12 (typically considered not liquefiable), and medium dense silty/sandy soils. Thus, we evaluated the liquefaction potential of the site using the UDOT SPLIQ spreadsheet

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

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(results are attached), applied to the saturated silty/sandy deposits. Our evaluation indicates saturated silty/sandy soils could liquefy between depths of 35 to 45 feet within B-5 during a major seismic event, with anticipated settlements in the range of 5.6 to 6.2 inches and about 2.25 inches of lateral spreading (deterministic method) at the top of the liquefiable soil layers. However, using the boundary curves provided by Ishihara6 for identifying when liquefaction-induced damage would occur at the surface (attached), it is our opinion that less than 1 inch of liquefaction-induced settlement will occur within 3 feet of the ground surface. Thus, it is our opinion that liquefaction mitigation is not needed for this site.

4.4 Other Geologic Hazards

No landslide deposits or features, including lateral spread deposits, are mapped on or adjacent to the site. The site is not located within a currently known or mapped potential debris flow, stream flooding, or rock fall hazard area.

5.0 SITE CONDITIONS

5.1 Surface Conditions

The north and south sides along the project alignment of 7000 South are currently landscaped primarily with cobbles/coarse gravels within the lower portions of the slopes, grasses within the upper portions, and occasional shrubs and trees. Based upon aerial photos dating back to 1997 that are readily available on the internet, the subject segment of 7000 South Street was constructed between 1997 and 2002, with the current slopes landscaped not long after the roadway was completed. This segment of the 7000 South alignment is bordered on the north and south existing residences (see Vicinity Map in Section 1.1 above).

5.2 Subsurface Soils

At the locations of the bore holes, we encountered approximately 1.5 to 2.5 feet of fill soils, which mostly consisted of silty gravel; these soils are considered undocumented/untested/non-engineered. A root mat/topsoil layer a few inches thick was typically encountered on top of the undocumented fill. We encountered natural soils beneath the topsoil/fill soils, consisting of CLAY with varying amounts of sand and gravel (CL, CH), Sandy SILT (ML), Clayey to Silty SAND (SC to SM) and a layer of Clayey GRAVEL with sand (GC) (in B-6), extending to the maximum depth penetrated of approximately 51.5 feet.

The silt/clay soils were moist to wet, brown to gray to black in color, and very soft to very stiff in consistency.

They also exhibited moderate over consolidation and strength characteristics with moderate compressibility characteristics.

6 Ishihara, K., 1985, Stability of Natural Deposits During Earthquakes, International Society for Soil Mechanics and Geotechnical Engineering, pp 321-376.

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The natural sand and gravel soils were slightly moist to wet, brown to gray in color, and loose to dense based on the blow counts in the bore holes. They will also exhibit moderately high strength and low compressibility characteristics.

For a more descriptive interpretation of subsurface conditions, please refer to the exploration logs, Figures 2 through 10, 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 encountered in bore holes B-1, B-2, B-4 and B-6 at depths of about 2.5 to 25 feet below existing grade at the time of our field exploration. On December 24, 2025, CMT personnel returned to the site to measure groundwater levels at depths ranging from 2.5 to 30 feet within slotted PVC pipes installed in the bore holes. These depths to groundwater could affect excavations and 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 (or topsoil) was encountered in the bore holes and will vary in extent and depth throughout the site. In addition, due to the potential for groundwater fluctuations, we recommend that the owner, owner’s representative or contractor verify soil and groundwater conditions upon commencement of construction activities.

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 loose and disturbed soils, topsoil, vegetation, etc. Based upon the conditions observed at the time of our subsurface exploration, approximately 1.5 to 2.5 feet of undocumented fill is present on the surface of the site (but may be locally deeper in some locations). The undocumented fill shall be removed from beneath the monument structure, but may remain in landscape areas.

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

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. Relatively shallow groundwater was encountered and later measured at a depth of 2.5 feet below the existing ground surface within B-1 but was otherwise 10 feet or deeper at other bore hole locations. We anticipate that excavations extending below a depth of about 2 feet at the east end of the project near the street level will likely encounter groundwater, and dewatering of such excavations will likely be required.

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.

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 fill materials must be free of sod, rubbish, topsoil, frozen soil, and other deleterious materials. Recommendations for the various fill types we anticipate will be used at this site are provided in the following table:

Geotechnical Engineering Study Page 12

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, a maximum Liquid Limit of 30 and a maximum Plasticity Index of 10.

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, a maximum Liquid Limit of 35 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).

Near-surface sand and gravel soils do not appear suitable for use as structural fill, but may be used as site grading fill and non-structural fill.

Near-surface 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 moisture-sensitive, which means they 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 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 92

7 American Association of State Highway and Transportation Officials

Geotechnical Engineering Study Page 13

LOCATION

TOTAL FILL

THICKNESS

(FEET)

MINIMUM PERCENTAGE

OF MAXIMUM DRY

DENSITY

5 to 8 95

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).

6.6 Stabilization

The near-surface 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.

8 American Public Works Association

Geotechnical Engineering Study Page 14

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 monument structure may be supported upon conventional isolated foundations placed on undisturbed natural soils and/or on select structural fill extending to undisturbed natural soils. The footing may be designed using a net bearing pressure of 2,000 psf. The term “net bearing pressure” refers to the pressure imposed by the portion of the structure located above lowest adjacent final grade, thus the weight of the footing and backfill to lowest adjacent final grade need not be considered. 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.

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.

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. If unsuitable soils (as listed above) are encountered, they must be completely removed and replaced with properly compacted structural fill. Excavation bottoms should be observed by a CMT geotechnical engineer to assess that undisturbed natural bearing soils have been exposed.

Geotechnical Engineering Study Page 15

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.

Where the structural fill thickness will be greater than 3 feet, 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. These settlements do not include liquefaction-induced settlements (see Section 4.3.3).

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 natural sand/gravel soils and structural fill, may be utilized for design. Passive resistance provided by properly placed and compacted structural fill above the water table may be considered equivalent to a fluid with a density of 425 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).

8.0 BLOCK WALL STABILITY AND RECOMMENDATIONS

8.1 Stability Parameters

The properties of the clay soils encountered at the site were tested for strength properties, as presented above in Section 3.3. To be conservative, we used the lower friction angle results of the two direct shear tests.

Accordingly, we used the following parameters in the stability analyses:

Geotechnical Engineering Study Page 16

Material

Internal Friction Angle (degrees)

Apparent Cohesion (psf)

Saturated Unit Weight (pcf)

On-Site Clay Soils 25 200 120

Verti-Blocks 0 (global)

45 (local)

9,000 (global)

0 (local)

For the seismic analysis, a peak horizontal ground acceleration (PGA) of 0.387g was obtained for a 7% exceedance in 75 years (return period of 1033 years) from the USGS hazards website9. Adjusting for Site Class D (see Section 4.2) with an FPGA of 1.1 results in a modified peak horizontal ground acceleration (PGAM) of 0.426g.

The pseudostatic coefficient for the seismic stability analysis was obtained using half (0.213) of the PGAM.

8.2 Stability Analysis

Using the input parameters presented above, the internal (block-to-block) stability of the wall was evaluated using the REA Analysis software considering sliding, overturning, and bearing capacity which implemented the LRFD factors per the 10th Edition of the AASHTO Bridge Design Specifications. The current 90% plans indicate that the maximum single-tier wall heights will be about 8 feet (total) while retaining maximum 2H:1V (Horizontal:Vertical) slopes. The results of this analysis for a single tier of Verti-blocks (see attached) indicate that maximum total heights of 4 feet can be achieved using the standard 36-inch deep blocks, 6 feet can be achieved using one lower row of 48-inch deep blocks with the other rows being 36-inch deep blocks, and 8 feet can be achieved using one lower row of 60-inch deep blocks with the other rows being 36-inch deep blocks.

We also evaluated the global stability of the block walls using limit equilibrium (Simplified Bishop) methods via the computer program SLIDE2 (version 9.0). The configuration we analyzed (located at about the middle of the north slope) consisted of a two-tiered wall having a total height of about 12 feet, split into two tiers having a total height of 6 feet each and separated by a minimum distance of 10 feet face to face, with the upper tier retaining a maximum 2H:1V slope (perpendicular to the wall). Typically, the required minimum factors of safety are 1.5 for static conditions and 1.1 for seismic (pseudostatic) conditions. The results of our analyses indicate that the proposed Verti-block wall will meet both these requirements provided our recommendations are followed. The slope stability graphs and input/output data are attached.

8.3 Verti-Block Wall Recommendations

Based on the results of our analysis, the Verti-block retaining walls at this site will be stable if constructed as follows (also see Figures 14 through 17, attached):

• The Verti-block walls may be constructed in one tier up to a maximum total height of 4 feet using the standard 36-inch deep blocks (Figure 14), 6 feet using one lower row of 48-inch deep blocks with the other rows being 36-inch deep blocks (Figure 15), and 8 feet using one lower row of 60-inch deep blocks with the other rows being 36-inch deep blocks (Figure 16). Two tiers of 6-foot high Verti-block walls can also be constructed as shown on the referenced plans.

9 https://earthquake.usgs.gov/hazards/interactive/

Geotechnical Engineering Study Page 17

• The lowest row of blocks should be embedded a minimum 12 inches below the lowest adjacent ground surface.

• The bottom row of blocks should be placed on a minimum 12 inches of crushed ¾-inch to 2-inch size angular clean gravel material. This material should be compacted until firm.

• Each row of blocks should be set back a minimum 2 inches from the underlying row of blocks.

• Drainage for each wall tier is recommended. The drain should consist of a perforated 4-inch minimum diameter pipe wrapped in fabric and placed at the bottom and behind the lowest row of blocks in each tier.

The pipe should daylight at one end of the wall or where the lowest point of the wall will be located and discharge to an appropriate drainage device or area. Clean gravel ¾- to 2-inch in size, with less than 10% passing the No. 4 sieve and less than 5% passing the No. 200 sieve, should be placed around the drain pipes and used to infill each of the Verti-blocks, as each row is placed. A fabric, such as Mirafi 140N or equivalent, should be placed at the back of the blocks between the clean gravel and the adjacent soils.

• Backfill materials behind the blocks may consist of on-site soils. If used, imported soils should have a maximum particle size of 3 inches, 70 percent or more passing the ¾-inch sieve and less than 30 percent fines (percent passing the No. 200 sieve). Backfill should be moisture conditioned to within 2 percent of optimum and compacted from 95% to 98% of the maximum dry density per ASTM D1557 (Modified Proctor).

• We recommend that CMT observe construction of the block walls at the following critical times: (1) when the lowest row of blocks has been placed along with the drain pipe and bottom gravel; (2) when the block wall is about halfway constructed; and (3) upon completion of the block wall construction.

9.0 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:

9.1 Field Observations

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

9.2 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

Geotechnical Engineering Study Page 18 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.

9.3 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.

10.0 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 appreciate the opportunity to be of service to you on this project. 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) 492-4132. To schedule materials testing, please call (801) 381-5141.

SUPPORTING

DOCUMENTATION APPENDIX

1CMT No.: 25557

70th South Landscape Project Jordan Canal to ±900 Feet West, West Jordan, Utah

SITE PLAN

Date: 25-Nov-2025

Figure:

N

B-1 B-2

B-3

B-4

B-5

B-6

HA-1HA-2

HA-3

Topsoil, 4" thick root mat Brown CLAY (CL), some sand and roots moist, medium stiff (estimated) 1

2 25 0 9 91 stiff (estimated) 3

5 28 0 6 94 27 19 8

END AT 10.5'

Remarks:

Equipment:

Excavated By:

Logged By:

Page:

70th South Landscape Project Total Depth:

Water Depth:

Coordinates: °, °

Test Pit Log

Hand Auger

10.5'

(see Remarks)

HA-1

Soil Description

Job #:

Date:

25557

11/24/25

Gradation Atterberg

Jordan Canal to ±900 Feet West, West Jordan, Utah

Groundwater not encountered during excavation.

Spencer Moon

Surface Elev. (approx): Not Given Spencer Moon

Figure:

D ep th ft

G R

A P

H

IC

LO

G

S am p le

T yp e

S am p le

M oi st ur e

D ry

D en si ty

(p cf

G ra ve l %

S an d

F in es

LL P

L

P I

Topsoil, 5" thick root mat

Brown CLAY with sand (CL), trace gravel, some roots moist, medium stiff (estimated)

6 12 2 20 78

REFUSAL AT 5.5'

Remarks:

Equipment:

Excavated By:

Logged By:

Page:

Total Depth: 5.5'

Water Depth:

Surface Elev. (approx): Not Given

Figure:

70th South Landscape Project Test Pit Log HA-2 Jordan Canal to ±900 Feet West, West Jordan, Utah

Soil Description

Date: 11/24/25

Gradation Atterberg

Job #: 25557(see Remarks)

Groundwater not encountered during excavation.

Spencer Moon

Spencer Moon

Coordinates: °, ° Hand Auger

D e pt h

(f t)

G R

A P

H

IC

L O

G

S a m p le T yp e

S a m pl e

M o is tu re

D ry

D e n si ty (p cf

G ra ve l %

S a n d

F in es

L L

P L

Topsoil, 3.5" thick root mat Brown Silty SAND (SM) slightly moist, medium dense (estimated)

Brown CLAY (CL), some sand 9 13 0 9 91 29 19 10 moist, medium stiff (estimated) stiff 10

Brown Silty SAND (SM) moist, medium dense (estimated)

11 8 0 68 32

Brown CLAY (CL), some sand 12 moist, stiff (estimated)

END AT 9.5'

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