13-Geotech Report - Slickrock Substation.pdf

New Slickrock Substation Location

Prepared by:

795 East Factory Drive St. George, UT 84790

Landmark Project No: 250144

Prepared for:

City of St. George Energy Services Barb Berrett, Chief Energy

Services Engineer 811 East Red Hills Parkway

St George, UT 84770

July 26, 2025

GEOTECHNICAL

INVESTIGATION REPORT

July 26, 2025

Barb Berrett, Chief Energy Services Engineer 811 East Red Hills Parkway St George, UT 84770 Subject: Geotechnical Investigation Report

New Slickrock Substation Location St. George, Utah Landmark Project No.: 250144

Barb, As requested, we have completed our Geotechnical Investigation for the above noted project.

Our geotechnical recommendations, along with our field and laboratory data are presented in this report.

Our field investigation consisted of the excavation of 3 test pits and 1 trench in the proposed substation footprint at Slick Rock Park in St. George, Utah. Borings of the bedrock layers for pole foundation design were completed for the previous site. Material encountered during our investigation for the substation contained silty sand overlaying weathered siltstone or mudstone with low plasticity. Groundwater was not encountered during our field investigation.

Spread footings established on structurally placed soils are recommended for structural support of the proposed structures. Design data for the self-supporting poles within the substation are also included in Section 6.0. Over-excavation, replacement, and recompaction of structure pads, as detailed in Section 5.0 of this report, will be required. The existing silty sands, free from organics and other debris, are suitable for use as structural fill.

Landmark has great interest in providing materials testing and special inspection services during the construction phase of this project. If you advise us of the appropriate time to discuss these engineering services, we will be pleased to meet with you at your convenience.

Please feel free to contact our office at (435) 986-0566 if you have any questions.

Sincerely, LANDMARK TESTING AND ENGINEERING

Steven Wells, P.E.

President / CEO i

TABLE OF CONTENTS

GEOTECHNICAL INVESTIGATION REPORT

NEW SLICKROCK SUBSTATION LOCATION

ST. GEORGE, UTAH

1.0 INTRODUCTION

2.0 PROPOSED CONSTRUCTION

3.0 SITE SETTING

3.1 SURFACE CONDITIONS

3.2 GEOLOGIC SETTING

3.3 GEOLOGIC HAZARDS

3.4 SEISMICITY

4.0 INVESTIGATION

4.1 FIELD INVESTIGATION

4.2 LABORATORY TESTING

4.3 ANALYSIS AND CONCLUSIONS

5.0 SITE GRADING AND EARTHWORK

5.1 GENERAL GRADING

5.2 FILL PLACEMENT AND COMPACTION

5.3 LIGHTLY LOADED ELEMENTS

5.4 CUT AND FILL SLOPES

6.0 FOUNDATION & CONSTRUCTION CONSIDERATIONS

6.1 SHALLOW FOUNDATIONS

6.2 DEEP FOUNDATIONS

7.0 FLOOR SLABS

8.0 LATERAL EARTH PRESSURES

9.0 MOISTURE CONTROL

10.0 SOIL CORROSIVITY

11.0 FOUNDATION REVIEW AND TESTING

12.0 LIMITATIONS

ii

TABLE OF FIGURES

GEOTECHNICAL INVESTIGATION REPORT

NEW SLICKROCK SUBSTATION LOCATION

ST. GEORGE, UTAH

APPENDIX A – Field Investigation

FIGURE A-1: Vicinity Map

FIGURE A-2: Site Map

FIGURES A-3 through A-5: Test Pit Logs

FIGURE A-6: Trench Cross-Section

FIGURE A-7: Unified Soil Classification System

GBA Information

APPENDIX B – Laboratory Test Results

TABLE B-1: Summary of Laboratory Test Results

Laboratory Test Reports (4 Pages)

APPENDIX C – LID Documents

Geotechnical Investigation Report

Landmark Project No. 250144

1.0 INTRODUCTION

This report presents the results of Landmark Testing & Engineering’s geotechnical investigation for the new Slickrock Substation Location in St. George, Utah. Figure A-1 is a Vicinity Map showing the project location relative to surrounding features. Figure A-2 is a Site Map showing the project limits and the approximate locations of the test pits and the trench completed for this investigation.

We have previously completed a Geotechnical Investigation Report for the previous site of the Slickrock Substation, Landmark Project No. 230534. Subsurface soils correlated well and consisted of sands and silts in the upper 1 to 5 feet of the trenches and borings. The sands and silts were underlain by siltstones, sandstones, and mudstones. The bedrock was typically weathered near the surface and graded harder with depth. The soils encountered in the test pits excavated in the pile of soil was very consistent and was fine grained clayey sand to sandy lean clay. Groundwater was not encountered in the borings, trenches, or test pits at the time of investigation. Information obtained from 230534 was used in the preparation of recommendations for this project.

This investigation was completed to assist in developing opinions and recommendations concerning site earthwork and foundation design.

2.0 PROPOSED CONSTRUCTION

We understand that the proposed development will consist of a new substation for St. George City Power on a 1.0-acre parcel. We anticipate that the proposed construction will include a precast concrete privacy wall, a masonry block control building, large pad-mounted transformers with containment berms, and various other pad and pole mounted structures. We anticipate pad loads will be up to 80 kips with bearing pressures on the order of 1,600 psf.

Any significant changes to the anticipated development should be reviewed by Landmark to evaluate the continued applicability of the recommendations contained in this report.

3.0 SITE SETTING

3.1 SURFACE CONDITIONS

The project site is located at 2395 East Riverside Drive in St. George, Utah, Parcel SG-5-2-28- 12071 and encompasses 14.9 acres, of which, only a 1.0-acre portion will be developed for the substation. The parcel is shared with Slick Rock Park to the northeast; however, the project location is on southwest side in a mostly undisturbed area which is approximately 1.0-acre in plan area. The project area has rolling hills that drop down to the southeast towards the street Riverside Drive. The site is bound by Slick Rock Park to the northeast, residential development to the north/northwest, Fossil Ridge Intermediate School to the west/southwest and commercial buildings across Riverside Drive to the south/southeast.

3.2 GEOLOGIC SETTING

According to the Utah Geological Survey,1 the project site is mapped as located on:

Jmw Whitmore Point Member (Lower Jurassic) – Interbedded, pale-reddish-brown, greenish-gray, and grayish-red mudstone and claystone, with thin-bedded, moderate-reddish-brown, very fine to fine-grained sandstone and siltstone and very light gray to yellowish-gray, dolomitic limestone; siltstone commonly thin bedded to laminated in lenticular or wedge-shaped beds; claystone is generally flat bedded and weathers into an expansive soil; contains several 2- to 6-inch-thick (5–15 cm), bioturbated, cherty, dolomitic limestone beds with algal structures, some altered to jasper, and fossil fish scales, likely of semionotid fish.

JTRmd Dinosaur Canyon Member (Lower Jurassic to Upper Triassic) – Interbedded, generally thin-bedded, moderate-reddish-brown to moderate-reddish-orange, very fine to fine-grained sandstone, very fine grained silty sandstone, and lesser siltstone and mudstone with laminated cross-beds; uniformly colored; ripple marks and mud cracks common; forms ledgy slope; regionally forms the base of Vermilion Cliffs step of the Grand Staircase; is poorly exposed in the northern part of the quadrangle in excavations below basalt talus near the south end of Middleton and West Black Ridges, in stream drainages on either side of the ridges, and where protected from erosion by overlying stream-terrace deposits, although several outcrops have recently been removed by construction; regionally, a thin chert pebble conglomerate marks the base of the unit, but in this area it is more common to have a 1.5- to 2-foot-thick (0.5–0.6 m) gypsum bed with local chert pebbles; unconformable lower contact is placed at the base of a chert pebble conglomerate or gypsum bed where recognized, otherwise it is placed at a prominent color and lithology change from reddish-brown siltstone.

Bedrock encountered at this site correlated well with these formations.

3.3 GEOLOGIC HAZARDS

The St. George basin lies within the transitional zone between the Colorado Plateau to the east and the Basin and Range Province to the west. Southwestern Utah is located on a structural block proximate to the southern segment of the Intermountain Seismic belt, which is characterized by high-angle normal faults that tend to step down to the west. The Hurricane fault with an offset of 6,000 to 8,000 feet forms the eastern edge of the transition zone. The Grand Wash-Reef Reservoir-Gunlock fault system with displacement of about 1,500 to 3,000 feet forms the western edge.

Fault Rupture The trace of the Washington fault is located approximately 2.0 miles east of the site and the projected trace of the Hurricane Fault is located approximately 12.5 miles east of the site. These faults displace late Quaternary sediments and are considered active. Strong ground motion associated with movement along the Hurricane, Volcano Mountain, Washington or other faults

1 Hayden, J.M. and Willis, G.C., 2011, Geologic Map of the St. George, Utah7.5-minute Quadrangle, Washington County, Utah; Utah Geological Survey Map DM-251 associated with the Intermountain Seismic Belt is possible however, the potential for surface fault rupture is considered low.

Liquefaction Liquefaction is the sudden loss of shear strength in the soil due to the build-up of excess pore water pressure. This can occur when the soil is subjected to intense shaking such as during a seismic event. The soils that are most susceptible to liquefaction are loose, saturated sandy soils with a low fines content (material passing the #200 sieve).

According to the Utah Geological Survey, the southwest portion of the project area is mapped as being in a zone of moderate liquefaction susceptibility. Soils encountered in the test pits, trenches and borings consisted of sands, silts, and clays underlain by sandstone, siltstone, and mudstone bedrock. Groundwater was not encountered in our explorations during our investigation. Given the shallow bedrock and the lack of groundwater, the liquefaction potential may be considered low. A liquefaction study is beyond the scope of this report.

Rockfall The development is not shown on the UGS geologic hazards map (Plate 5) as not being located within a high rockfall hazard area. A specific rockfall hazard analysis is beyond the scope of this report. There is an elevated section of land along the western portion of the north side of the project site with surficial rock. This could pose a potential rock fall hazard to the site. A rock fall study is beyond the scope of this report.

Landslides The site is shown on the UGS geologic hazards map (Plate 2) as not being located partially within landslide hazard area.

Expansive soils The site is shown on the UGS geologic hazards map (Plate 6) as being located in a moderate to highly expansive soil hazard area. Expansive soils are clays and mudstones which changes volume due to moisture content changes. The clays and mudstone encountered in our and test pits has a low plasticity and has not been found to be expansive.

Collapsible Soils The southwest portion of the site is shown on the UGS geologic hazards map (Plate 7) as being located in a Type 1 Collapsible Soil hazard area. Collapsible soils are considered to have considerable strength when in a dry, natural state, but that significantly settle due to hydro compaction, reduction of air space when the soil is wetted.

The surficial silty sands are loose, and are generally collapsible. Recommendations for over-excavation and recompaction of these soils are detailed in Section 5.0

3.4 SEISMICITY

The State of Utah adopted ASCE 7-22 and the IBC 2024 on July 1, 2024. Individual cities may not have adopted these codes at this time. We are providing seismic design values for both code sets; Landmark defers to the Structural Engineer of Record for determination of the relevant building code used for the project.

Seismicity at the site was determined using the Seismic Maps Tool from seismicmaps.org website.

The following values are presented to assist with seismic design:

IBC 2024

• Latitude = 37.10290° North, Longitude = 113.53505° West

• Site Class = C, based on ASCE 7 as referenced in 2024 IBC

Period (sec) Sa (g) Site Class

0.2 SS = 0.55 B/C

1.0 S1 = 0.16 B/C

0.2 SDS = 0.40 C

1.0 SD1 = 0.15 C

IBC 2021

• Latitude = 37.10290° North, Longitude = 113.31286° West

• Site Class = C – Very Dense Soil and Soft Rock based on ASCE 7-16 as referenced in 2021

IBC

Period (sec) Sa (g) Site Class

0.2 SS = 0.531 B/C

1.0 S1 = 0.172 B/C

0.2 SDS = 0.456 C

1.0 SD1 = 0.172 C

As per Section 20.1 of ASCE 7-22, “The site soil shall be classified in accordance with Table 20.2- 1 and Section 20.2 based on the average shear wave velocity parameter, νs, which is derived from the measured shear wave velocity profile from the ground surface to a depth of 100 ft. Where shear wave velocity is not measured, approximate generalized correlations between shear wave velocity and standard penetration test (SPT) blow counts, Cone Penetrometer Test (CPT) tip resistance, shear strength, or other geotechnical parameters shall be used to obtain an estimated shear wave velocity profile. Where the soils properties are not known in sufficient detail to determine the site class, the most critical site conditions of Site Class C, Site Class CD and Site Class D, as defined in Section 11.4.2, shall be used unless the Authority Having Jurisdiction or geotechnical data determine that Site Class DE, E, or F soils are present at the site.” Based our engineering experience in the area, mapped geology and the blow counts and soils encountered in the borings it is the opinion of Landmark Testing and Engineering that the soils on site classify as Site Class C.

4.0 INVESTIGATION

4.1 FIELD INVESTIGATION

To investigate the subsurface conditions, 3 test pits and one trench were excavated to a depth of

5.5 to 7.0 feet. Test pits were excavated using a Volvo EC1600 mini ex with an 24-inch toothed bucket. Depending on subsurface conditions, bag or block samples of soil were obtained from the test pit excavations. Approximate test pit locations are shown on Figure A-2.

A Landmark geologist, Micheal Meyers, G.I.T., supervised the excavation of the test pits and trench. A log of the subsurface conditions was prepared, samples collected sealed for transport, and relevant site photographs taken.

Materials encountered during the Slick Rock investigation were medium dense silty sands underlaid by weathered to firm mudstone. The test pits have shown relatively the same, and each met refusal on silty mudstone bedrock. The material encountered in the trench was silty sands overlaying sandstone or mudstone bedrock, continuing the trend.

Groundwater was not encountered at the time of investigation.

The Logs of Test Pits are presented on Figures A-3 through A-5. A cross section of the trench is present as Figure A-7. A key to the soil classifications used on the logs is presented on Figure A-8.

4.2 LABORATORY TESTING

Soil samples from the test pits were taken to our St. George, Utah laboratory for testing. Tests performed on the samples included:

• Moisture content and unit weight for density determination

• Sieve analysis and Atterberg Limits for soil classification

• One-Dimension Consolidation for earthwork design

• Modified Proctor for construction testing

• Soluble Sulfate Content for concrete mix design selection

Soil Classification Tests Soil classification tests were performed on a total of four (4) samples collected during the field exploration. Samples were tested for moisture content, grain size analysis by mechanic sieve, and plasticity testing by Atterberg Limits. The classification was then determined according to the Unified Soil Classification System (USCS). This testing was done in accordance with ASTM C136 and C 117. A summary of the classification testing is provided as follows:

Test Pit No.

Depth (ft.)

Moist.

Gravel

Sand

Fines

Liquid Limit

Plastic Index

USCS

Classification

TP-1 4.0 11.2 0 65 35 32 13 Clayey Sand (SC)

TP-2 4.0 33.3 0 34 66 22 6 Sandy Silty Clay

(CL-ML)

TP-3 4.5 9.3 1 66 33 27 8 Clayey Sand (SC)

Test Pit No.

Depth (ft.)

Moist.

Gravel

Sand

Fines

Liquid Limit

Plastic Index

USCS

Classification

TR-1 0+98 -- -- -- -- NP NP --

One-Dimension Consolidation Tests Consolidation testing was not performed samples collected during the geotechnical exploration due to the shallow bedrock and low plasticity of the samples collected.

Water-Soluble Sulfate Content Tests One sample was tested for water-soluble sulfate content during the previous investigation. These sulfates are known to be corrosive to concrete and metal, and special accommodations should be made for corrosive soils according to the American Concrete Institute. Testing was completed in accordance with ASTM C1580. A summary of sulfate test results is provided as follows:

Test Pit No. Depth (ft.) Sulfate Content (%) Exposure Class

B-5 2.5 0.3 S2

In general, soils on site were tested and considered to have moderate to high corrosive potential.

For recommendations, refer to Section 12.0.

Modified Proctor Test A modified Proctor test was performed on a bulk sample collected during the field exploration.

This testing is done by placing material in a mold and compacting it to the percent compaction and molding water content needed to achieve the required engineering properties, and for controlling construction to assure that the required compaction and water contents are achieved. This test was done in accordance with ASTM D1557: Method B.

Test Pit No. Depth (ft.) Maximum Dry Density, Lbs/ft3 Optimum Moisture, %

TP-2 Bulk 125.8 8.8

The results of the laboratory tests are shown on the Test Pit Logs and the Trench Cross-section on Figures A-3 through A-6 and on the Summary of Laboratory Test Results on Table B-1.

Individual test results are also included in Appendix B.

4.3 ANALYSIS AND CONCLUSIONS

Our field and laboratory tests results indicate the soils on site consisted of predominately loose to dense sand, silt, and clay underlain by various bedrock formations. The soils encountered in the test pits excavated in the large soil pile on-site consisted of clayey sand to sandy lean clay.

Surficial soils were loose to medium dense and likely to collapse or compress under the loads of the transformers and other equipment. The soil in the large pile on site is suitable for use as fill in the lower portion of the backfill, provided it is placed according to structural fill standards as subsequently outlined.

We recommend that loose, surficial soils beneath the substation equipment be excavated prior to construction. General recommendations for the earthwork and the foundation system are outlined in Sections 5.0 and 6.0 of the report.

5.0 SITE GRADING AND EARTHWORK

5.1 GENERAL GRADING

Prior to general site grading, the project site should be cleared and grubbed of all vegetation in all building areas, including roadways, and concrete flat work. Following clearing and grubbing, we recommend that the soils within the building areas be excavated down to moderately competent bedrock. We anticipate that between 2 and 5 feet of excavation will be required for the site.

Following excavation, the excavated soils may be used as structural fill in the lower portion of the backfill. Due to the high fines content of the on-site soils, we anticipate that compaction will be difficult to achieve and structure moisture control will be necessary. We recommend a minimum of 1 foot of imported, granular, structural fill be placed immediately below all footings and floor slabs.

Landmark does not determine the location of the over-excavations or the location of the structures to be constructed. The contractor is responsible to ensure that the structures are placed entirely within the over-excavated and recompacted building pads.

Following over-excavation, a Landmark engineer or geologist should observe the excavation to document the depth of over-excavation, and determine if subsurface conditions match those found in our filed investigation. Alterations to our recommendations may be required if substantially different conditions are encountered.

5.2 FILL PLACEMENT AND COMPACTION

All fill to be placed for support of footings and slabs-on-grade should be considered structural fill.

On-site soils are suitable for use as structural fill at depth. However, we recommend that the floor slabs and footings be established on imported, granular fill due to corrosive onsite soils. St.

Geroge City Standard Specification roadbase is suitable for use as imported fill below concrete.

Imported, granular fill, should be well-graded, non-expansive, and free of organics and all deleterious materials. Soils used for imported, granular fill should meet the following specifications and preferably would classify as gravel.

GRADATION PERCENT PASSING

3- inch 100

1.5-inch 80-100

No. 200 sieve 10-25

ATTERBERG LIMITS

Liquid Limit 30 or less Plasticity Index 9 or less

Material not meeting the above requirements may be suitable for use as structural fill at the discretion of the geotechnical engineer. Samples of structural fill should be submitted for testing prior to transporting to the site.

Any on-site soils used as structural fill or imported, granular fill should be compacted to the following specifications.

FILL PLACEMENT AND COMPACTION

Maximum lift thickness 8-inch (loose) Minimum compaction 95% ASTM D-1557

Compacted Moisture Content within 2% of optimum

Compaction of structural fill should be completed with equipment suitable for the conditions encountered in the field such that compaction requirements are met, including those areas that may be inaccessible to large rolling compactors. All structural fill should be evenly spread on a horizontal plane in eight-inch loose lifts. Each eight-inch lift of structural fill material placed at the site should be tested for compliance with the required relative compaction and moisture content prior to proceeding with additional lifts.

5.3 LIGHTLY LOADED ELEMENTS

Exterior concrete slabs on grade (sidewalks, curbs, gutters, and misc.) should be established on a minimum of 12-inches of structurally placed soils with a maximum particle size of 3-inches.

Sidewalks will need to be underlain by approved road base as per St. George City Standards.

Structural fill, including road base, should be compacted to a minimum of 95 percent of the maximum dry density as determined by ASTM D-1557.

5.4 CUT AND FILL SLOPES

It is recommended that permanent cut or fill slopes in silty sand soil be maintained at a slope of two horizontal to one vertical (2H:1V) or flatter unless structurally retained. Permanent slopes in competent bedrock may be maintained at slopes of one horizontal to two vertical (1H:2V).

Grading of both cut and fill slopes should be such that surface water is directed away from the slopes and not concentrated on slopes or in unprotected channels. Construction procedures should ensure adequate compaction of slope faces. All excavations should conform to OSHA standards.

6.0 FOUNDATION & CONSTRUCTION CONSIDERATIONS

6.1 SHALLOW FOUNDATIONS

The proposed structures may be supported on conventional spread or continuous footings established on structurally placed soils. Foundation excavations should be visually observed and tested by qualified personnel prior to placement of reinforcing steel or concrete. Additional foundation recommendations are subsequently presented.

DESCRIPTION VALUE

Foundation Type Continuous or spread footings Bearing Material Structurally placed soils Allowable Bearing Capacity 2,500 psf on Structurally placed soils Minimum embedment depth below finished grade 12 inches (for frost and confinement)

Minimum footing width 12 inches (continuous) for single-story 24-inches (isolated spread)

Total estimated settlement 1-inch Total differential settlement less than 3/4 inch

The allowable bearing capacity is based upon dead load plus long-term live load. A one-third increase in allowable bearing capacity for short duration loads such as wind or seismic loads is permitted with the alternative load combinations given in Section 1605.3.2 of the IBC.

6.2 DEEP FOUNDATIONS

We anticipate that towers will be supported on drilled caisson pier foundations. Based on 2024 IBC Table 1806.2, caissons embedded in silt may be designed with vertical foundation pressure of 1,800 psf and a lateral bearing pressure of 100 psf per foot below the natural grade. The upper 5 feet of soil should be discounted for unsuitable soils or frost action. Foundation excavation should be visually observed and tested by qualified personnel prior to the placement of reinforcement and concrete. Additionally, we have provided LPILE parameters for each soil type encountered during our investigation for design in the below table.

Soil Type

Total Unit

Weight (pcf) ε50 (in/in)

K value (lb/in^3)

Friction Angle

Cohesion (psf)

Unconfined Compressive Strength (psi)

Modulus of Elasticity

(psi)

SM/ML 105.0 0.002 60 31 n/a n/a 5,500 Bedrock 120.0 0.002 2,000 10 5,000 70 2,000,000

7.0 FLOOR SLABS

It is recommended that concrete floor slabs be constructed on a pad that has been prepared as previously indicated. A minimum of 4-inches of relatively free-draining material should be used beneath the slab in order to help distribute floor loads, break the rise of capillary water, and aid in the concrete curing process. Alternatively, 6 inches of road base may be used in place of the free draining-material. The thickness of the free-draining material may be included in the 12-inches of granular, structural fill.

Concrete slabs should be designed using rebar reinforcement and frequent crack control joints to help control normal shrinkage and stress cracking. Concrete placement and curing should meet ACI2 requirements including following hot or cold weather placement recommendations, when appropriate.

2 American Concrete Institute

8.0 LATERAL EARTH PRESSURES

Lateral loads imposed on footings may be resisted by the development of passive earth pressures against the sides of footings and friction between the base of the footing and the supporting soils.

Lateral earth pressure values are presented in the following table.

Case Evaluated Soil Type Value

Active On-site Soils 38 psf/ft

57 psf/ft (with seismic) At-Rest On-site Soils 58 psf/ft

Passive On-site Soils 375 psf/ft

323 psf/ft (with seismic) Coefficient of friction tan(φ*0.6) where φ = 31° On-site Soils 0.34

The lateral earth pressures presented do not include any safety factors except where the friction angle (φ) used to determine the coefficient of friction has been multiplied by 0.6 to account for smooth contact conditions. The pressures also assume horizontal backfill and that the backfill is in a drained condition with no build-up of hydrostatic pressure. The additional effects of sloping backfill, surcharge, structural loads and groundwater conditions should be included in calculating lateral earth pressures. Backfill should be placed in accordance with the requirements of structural fill except that backfill in landscape and areas that will not be subject to structural loadings may be reduced to 90 percent of the maximum dry density as determined by ASTM D- 1557.

9.0 MOISTURE CONTROL

This soils report provides recommendations for site preparation and foundation design.

Inadequate surface drainage or failure to control moisture will result in excessive differential movement of slabs, walkways, porches, or patios and structural damage, regardless of the site preparation. The following moisture control measures are recommended:

(1) Once the finish floor elevation has been established, the site grades should be constructed and maintained to drain surface and roof runoff away from the building foundation at a slope of 5 percent for at least 10 feet beyond the structure. The ground surface should be graded to drain away from the building in all directions.

Water should not be allowed to pond adjacent to foundations or on-site.

(2) Inadequate compaction of utility trench backfill provides a conduit for water migration. All utility trenches within the building footprint and extending 5 feet beyond the footprint should be backfilled with structural fill similar to that approved for the foundations. Backfill adjacent to structures should be compacted to at least 90 percent of the maximum dry density as determined by ASTM D-1557 and the minimum slope requirements should be followed. Backfill beneath structures should be compacted to at least 95 percent of the maximum dry density.

(3) Grading should be such that surface water is directed away from all cut and fill slopes and collected only in channels protected against erosion. Water should not be allowed to pond on-site.

(4) Unless roof runoff falls on impervious surfaces such as asphalt or concrete that are sloped away from the building for a distance of 10 feet, roof runoff should be collected and discharged well outside of the foundation backfill limits.

It should be emphasized that final grading and landscaping generally occurs after construction of the structure and observation of these features is outside of normal geotechnical inspection and observation. The owner/contractor is responsible to ensure that these surface drainage and moisture control recommendations are followed throughout the life of the structure.

10.0 SOIL CORROSIVITY

Soils from the project site were tested for water-soluble sulfates content. The percent of water-soluble sulfates in the soil is 0.3 which is considered severe according to ACI 318. We recommend that concrete mixes used on the project be designed in accordance with ACI 318 Table

19.3.1.1 for Sulfate Exposure Class S2. We recommend that buried pipes be plastic (PVC or HDPE) instead of metal, where possible.

11.0 FOUNDATION REVIEW AND TESTING

This report has been prepared to assist in project design and construction. Variations from the conditions portrayed in the exploratory investigations may occur which are sometimes sufficient to require modifications to the design. In order to incorporate recommendations provided into actual field conditions and to confirm that the project specifications are implemented, we recommend that observation and testing be performed during construction to monitor over-excavation, grading, and preparation of soils upon which foundations elements or structural loads may be established.

12.0 LIMITATIONS

The exploratory data presented in this report were collected to provide geotechnical design recommendations for this project and subsurface site descriptions represent conditions observed at the time and at the locations explored. The investigations may not be indicative of subsurface conditions beyond the investigation location and conditions may change with passage of time. If subsurface conditions are encountered that are significantly different than those reported herein, Landmark should be contacted immediately for the continued applicability of the recommendations. In the event changes to the project are made that differ from those presented in this report, Landmark should be made aware of the changes. Landmark will provide written verification that the recommendations and conclusions remain valid or that modifications are required.

This report has been prepared to assist in project design and construction. We respectfully request the opportunity to review the final design drawings and specifications in order to determine whether the assumptions and recommendations presented herein are applicable to the anticipated designs.

Landmark Project No. 250144

This report is not intended to be used as the sole bid document. Any information concerning the environmental conditions of the site is beyond the scope of this geotechnical study. This geotechnical report has been prepared to meet the specific needs of our client and may not be appropriate to satisfy the needs of other users.

Site conditions and standards of practice change, therefore, we should be notified to review and update the report and its recommendations if construction is not commenced within 3 years of the date it was issued.

LANDMARK TESTING & ENGINEERING

John M. Anderson, P.E.

Professional Engineer

Reviewed by:

Kent R. Nelson, P.E.

Professional Engineer

7/26/2025

APPENDIX A

Field Investigation

Vicinity Map Landmark Project No 250144

Figure A-1

N

Project Sites

Site Map Landmark Project No 250144

Figure A-2

D ep th (ft

So il Sy m bo l

Sa m pl es

BG

BG

Ground Surface

Lithologic Description

FILL: Silty SAND (SM) Medium dense, slightly moist, fine to medium grained sand, fine roots and pinholes down to 4 feet, light reddish brown, easy digging

NATIVE: Clayey SAND (SC) Medium dense, slightly moist, fine to medium grained, light reddish brown, easy digging

Total Test Pit Depth at 6' Refusal on Siltstone/Silty Mudstone

Sa m pl e D ry D en sit y

(p cf

M oi st ur e

11.2

At te rb er g

Li m its

LL

PI

32 13

Gr av el

Sa nd

#2 Fi ne s

Co ns ol id at io n

M od ifi ed

Pr oc to rM ax

D ry D en sit y (p cf

O pt im um

M oi st ur e

W at er -S ol ub le Su lfa te

CB

R

R

SL

og

La nd m ar k Te st P it

- W ith L ab R es ul ts

N O

E

LE

VA

TI

O N

S / l an dm ar k-te st in g-an d-en gi ne er in g

/ a dm in

Ju ly

7, :3

AM

TP-1TEST PIT NUMBER

DATE: 2025-06-19 EXCAVATOR: Infinex Excavation EQUIPMENT: Volvo EC 1600

LATITUDE/LONGITUDE: 37.10231 -113.53508

GROUNDWATER:

LOGGED BY: Michael Meyers

REVIEWED BY: John Anderson NOTES: feet below surface

Various Pole Foundations - I-15, Bluff St, Slick RockPROJECT NAME:

City of St. George Energy ServicesClient:

Project No.: 250144

Project Location: St. George, Utah th (ft

So il Sy m bo l

Sa m pl es

B

BG

BG

Ground Surface

Lithologic Description

FILL: Silty SAND (SM) Loose, slightly moist, fine to coarse grained with gravel, fine roots down to 2 feet, reddish brown, easy digging

NATIVE: Silty SAND (SM) Loose, slightly moist, fine to medium grained, oriented gravel, light brown, easy digging

Sandy Silty CLAY (CL-ML) Soft to medium stiff, slightly moist, fine grained, rare 1/4" roots down to 4.5 feet, light brown, easy digging

Total Test Pit Depth at 5.5' Refusal on Siltstone/Silty Mudstone Bedrock

Sa m pl e D ry D en sit y

(p cf

M oi st ur e

33.3

At te rb er g

Li m its

LL

PI

22 6

Gr av el

Sa nd

#2 Fi ne s

Co ns ol id at io n

M od ifi ed

Pr oc to rM ax

D ry D en sit y (p cf

125.8

O pt im um

M oi st ur e

8.8

W at er -S ol ub le Su lfa te

CB

R

R

SL

og

La nd m ar k Te st P it

- W ith L ab R es ul ts

N O

E

LE

VA

TI

O N

S / l an dm ar k-te st in g-an d-en gi ne er in g

/ a dm in

Ju ly

7, :3

AM

TP-2TEST PIT NUMBER

DATE: 2025-06-19 EXCAVATOR: Infinex Excavation EQUIPMENT: Volvo EC 1600

LATITUDE/LONGITUDE: 37.10193 -113.53465

GROUNDWATER:

LOGGED BY: Michael Meyers

REVIEWED BY: John Anderson NOTES: feet below surface

Various Pole Foundations - I-15, Bluff St, Slick RockPROJECT NAME:

City of St. George Energy ServicesClient:

th (ft

So il Sy m bo l

Sa m pl es

BG

BG

Ground Surface

Lithologic Description

FILL: Silty SAND (SM) Medium dense, slightly moist, fine to medium grained, fine roots to 1/8" in diameter and pinholes down to 3.5 feet, reddish brown

Some gravels and cobbles at 3 feet

NATIVE: MUDSTONE Weathered to Clayey SAND (SC) Weathered, slightly moist, fine to medium grained, vertical calcium strip, light brown

Total Test Pit Depth at 7' Refusal on Siltstone Bedrock

Sa m pl e D ry D en sit y

(p cf

M oi st ur e

9.3

At te rb er g

Li m its

LL

PI

27 8

Gr av el

Sa nd

#2 Fi ne s

Co ns ol id at io n

M od ifi ed

Pr oc to rM ax

D ry D en sit y (p cf

O pt im um

M oi st ur e

W at er -S ol ub le Su lfa te

CB

R

R

SL

og

La nd m ar k Te st P it

- W ith L ab R es ul ts

N O

E

LE

VA

TI

O N

S / l an dm ar k-te st in g-an d-en gi ne er in g

/ a dm in

Ju ly

7, :3

AM

TP-3TEST PIT NUMBER

DATE: 2025-06-19 EXCAVATOR: Infinex Excavation EQUIPMENT: Volvo EC 1600

LATITUDE/LONGITUDE: 37.10226 -113.53416

GROUNDWATER:

LOGGED BY: Michael Meyers

REVIEWED BY: John Anderson NOTES: feet below surface

Various Pole Foundations - I-15, Bluff St, Slick RockPROJECT NAME:

City of St. George Energy ServicesClient:

+5

+10

+15

+20

0+00 0+05 0+10 0+15 0+20 0+25 0+30 0+35

Surface Fault Rupture Hazard Evaluation Landmark Project No 250144

Trench 1 Sheet 1

Scale in Feet

Scale 1 inch equals 5 feet with no vertical exaggeration.

Trench Logged by Micheal Meyers, G.I.T on June 19, 2025

37.102425, -113.534608

0+40

1. Fill: Silty Sand: Loose to medium dense, slightly moist, fine to medium grained, light reddish brown

Level Line

FILL

2. Native 1. SM: Loose, slightly moist, fine to coarse grained with gravel, alluvial deposits, well-oriented gravels, light brown

3. Mudstone: Highly weathered, weak to moderately strong, slightly moist, fine grained, brown to reddish brown

+5

+10

+15

+20

0+40 0+45 0+50 0+55 0+60 0+65 0+70 0+75

Surface Fault Rupture Hazard Evaluation Landmark Project No 250144

Trench 1 Sheet 2

Scale in Feet

Scale 1 inch equals 5 feet with no vertical exaggeration.

Trench Logged by Micheal Meyers, G.I.T on June 19, 2025

N

0+80

FILL

1. Fill: SM: Loose to medium dense, slightly moist, fine to medium grained, light reddish brown

2. Native 1. SM: Loose, slightly moist, fine to coarse grained with gravel, alluvial deposits, well-oriented gravels, light brown

3. Mudstone: Highly weathered, weak to moderately strong, slightly moist, fine grained, brown to reddish brown

Level Line

Boulder

+5

+10

+15

+20

0+80 0+85 0+90 0+95 1+00 1+05 0+75

Surface Fault Rupture Hazard Evaluation Landmark Project No 250144

Trench 1 Sheet 3

Scale in Feet

Scale 1 inch equals 5 feet with no vertical exaggeration.

Trench Logged by Micheal Meyers, G.I.T on June 19, 2025

37.102177, -113.534424

1+10

N

Boulder

FILL

1. Fill: SM: Loose to medium dense, slightly moist, fine to medium grained, light reddish brown

3. Mudstone: Highly weathered, weak to moderately strong, slightly moist, fine grained, brown to reddish brown

4. Sandstone: Weak to strong, slightly moist, fine grained, orange to light brown

2. Native 1. SM: Loose, slightly moist, fine to coarse grained with gravel, alluvial deposits, well-oriented gravels, light brown

Level Line

U S C S S u m m a r y

Clayey sands, sand-clay mixtures

Inorganic silts, micaceous of diatomaceous fine sand or silty soils, elastic silts

Inorganic clays of high plasticity, fat clays

Organic clays of medium to high plasticity, organic silty clays, organic silts

Peat and other highly organic soils

Coarse

GRAIN SIZE CHART

SYMBOLS

UNIFIED SOIL CLASSIFICATION SYSTEM

4.76 to 0.074

3/4" to No. 4

3" to 3/4" 76.2 to 19.1

3" to No. 4 76.2 to 4.76

12" to 3" 305 to 76.2

Above 12" Above 305

Range of Grain Size U.S. Standard

Sieve Size Grain Size in Millimeters

MAJOR DIVISIONS

No Recovery

Core

Bucket Sample

Auger Cuttings

Bag Sample

Block Sample

PLASTICITY CURVE

GW

GP

GM

Organic silts and organic silty clays of low plasticity

GC

C O

A R

SE

-G

R A

IN

E

D S

O

IL

S (M or e th an

0% o f so il

R et ai ne d on

N o.

s ie ve s iz e)

SILT & CLAY

Fine Medium Coarse

SAND

Fine

GRAVEL

COBBLES

BOULDERS

CLASSIFICATION

HIGHLY ORGANIC SOILS

S

IL

T S

C

L A

Y S

L iq ui d

L im it

S

IL

T S

C

L A

Y S

L iq ui d

L im it

S A

N D

S M or e th an

/2 o f co ar se f ra ct io n

N o.

si ev e si ze

G R

A V

E L

S M or e th an

/2 o f co ar se f ra ct io n

N o.

si ev e si ze

Below No. 200

No. 40 to No. 200 0.420 to 0.074

Below 0.074

No. 10 to No. 40 2.00 to 0.42

No. 4 to No. 10 4.76 to 2.00

No. 4 to No. 200

19.1 to 4.76

Relatively Undisturbed Sample

SAMPLES

TYPICAL NAMES

SW

SP

SM

SC

Inorganic silts and very fine sands, rock flour, silty fine sands or clayey silts with slight plasticity

F

IN

E -G

R A

IN

E

D S

O

IL

S (L es s th an

0% o f so il

R et ai ne d on

N o.

s ie ve s iz e)

ML

CL

OL

MH

CH

OH

PT

Clayey gravels, gravel-sand-clay mixtures

Silty gravels, gravel-sand-silt mixtures

Poorly graded gravels or gravel-sand mixtures little or no fines.

Well graded gravels or gravel-sand mixtures little or no fines.

Well graded sands or gravelly sand mixtures little or no fines.

Silty sands, sand-silt mixtures

Poorly graded sands or gravelly sand mixtures little or no fines.

Inorganic clays of low to medium plasticity, gravelly clays, sandy clays, silty clays, lean clays.

Clayey sands, sand-clay mixtures

P la st ic it y

In d ex

Liquid Limit 0 10 20 30 40 50 60

"U " L in e

MH or OH

70 80 90 110

"A " L in e

ML or OL

C H o r

O H

CL-ML

C L o r O

L

Landmark Testing & Engineering 795 Factory Drive St. George, UT 84790 Telephone: 435-986-0566 Website: www.landmarktesting.com

APPENDIX B

Laboratory Test Results

SUMMARY OF LABORATORY

TEST RESULTS

7/26/2025Date of Report:

250144Project #:

U nc on fin ed

C om pr es si ve

S tr en gt h (p sf

795 East Factory Drive, St. George, UT 84790 ● Phone: (435) 986-0566 ● Fax: (435) 986-0568

TABLE B-1

TR-1 0+89'

ML A-4(0)

TP-3 4.5'

50.0

TP-1 4.0'

TP-2 4.0' 5.3 2.0 48.0

Pe rc en t F in er

T ha n 0.

m m

So ol ub le

S ul fa te

C on te nt

TP-2 Bulk

U

SC

S G ro up

S ym bo l

A A

SH

TO

S oi l C la ss ifi ca tio n

G ra ve l (

Sa nd

Fi ne s

Li qu id L im it

Pl as tic ity

In de x

M ax im um ry en si ty (p cf

O pt im um

M oi st ur e

C on te nt

C B

R V al ue

St. George, UT 84770

Project: Various Pole Foundations – I-15, Bluff St, Slick Rock

Client: City of St. George Energy Services

811 East Red Hills Parkway

Location:

B or in g

/ T es t P it

N um be r

D ep th B el ow

G ro un d

Su rf ac e

(ft

M oi st ur e C on te nt

In -P la ce

D ry

D es ni ty

(p cf

Mechanical Gradation Atterberg Limits

Sw el l-C on so lid at io n Sw el l/C ol la ps e

W et tin g

Lo ad

(S /C k sf

Modified Proctor / CBR

795 East Factory Drive, St. George, UT 84790 ● Phone: (435) 986-0566 ● Page 1 of 1

Maximum Dry Density, Lbs/ft 3 125.8

Optimum Moisture, % 8.8

Test Standard ASTM D 1557

Method Test Performed on

Material Passing:

3/8 in. Sieve

25 blows

This report reflects the results of the material at the location indicated on the date sampled.

Method B

% Oversized: #VALUE!

Oversize Sp. G.:

This report shall not be reproduced, altered, or redistributed without written consent from Landmark Testing and Engineering

ZAV Sp. G.: 2.59

N/A

Mold Size (cu. Ft.): 0.033333 Test Results

Number of Layers: 5 layers

Blows per Layer:

Hammer Weight: 10 pounds

Hammer Drop: 18 inches

% Moisture 5.7 8.2 10.6 12.5

120.4Dry Density 123.2 125.7 124.6

2 3 4 5Point 1Proctor Data 6

Type of Sample: Red-Brown Silty, Clayey Sand Tested By: J. Wells Date: 6/23/2025

Location of Sample: Test Pit 2 at Bulk Authorized By: Client Date: 6/20/2025

St. George, UT 84770 Lab#: 25SG4049

Project: Various Pole Foundations – I-15, Bluff St, Slick Rock Project #: 250144

Location: St George Sampled By: M. Meyers Date: 6/20/2025

PROCTOR REPORT

Client: City of St. George Energy Services Date of Report: 6/25/2025

811 East Red Hills Parkway Reviewed By: Z. Girsberger

5 6 7 8 9 10 11 12 13 14 p c f

% Moisture

Moisture Density Relationship

St. George, UT 84770

This report reflects the results of the material at the location indicated on the date sampled.

This report shall not be reproduced, altered, or redistributed without written consent from Landmark Testing and Engineering

795 East Factory Drive, St. George, UT 84790 ● Phone: (435) 986-0566 ● Page 1 of 1

75 µm #200 35.1

300 µm #50 63

Diameter

D10

Coefficient of

Concavity, CC

Coefficient of

Uniformity, CU

Diameter

D60

Diameter

D30425 µm #40 74

1.18 mm #16 94

0.0 0.0

% Cobble

> 3"

% Gravel

< 3" - #4

% Sand

< #4 - #200

% Silt-Clay

< #200

64.9 35.1

2.00 mm #10 97

4.75 mm #4 100

9.5 mm 3/8" 100

19 mm 3/4"

12.5 mm 1/2"

25 mm 1" AASHTO Classification System A-2-6(1)

ASTM D 2487

50 mm 2" Plasticity Index 13

AASHTO M145

ASTM D 4318

37.5 mm 1-1/2" Unified Classification System SC

150 mm 6" Natural Moisture Content, %

75 mm 3" Liquid Limit 32 ASTM D 4318

11.2 ASTM D 2216

Location of Sample: Test Pit 1 at 4.0' Authorized By: Client Date:

Test Standard

6/20/2025

Sieve Analysis , ASTM C136 and C117

Sieve Size % Passing

Cumulative Specification Test Result Specification

Location: St George Sampled By: M. Meyers Date: 6/20/2025

Type of Sample: Red Clayey Sand Tested By: A. Pay Date: 6/23/2025

SOIL CLASSIFICATION REPORT

Date of Report: 6/25/2025

Reviewed By: Z. Girsberger

Lab#: 25SG4048

Project: Various Pole Foundations – I-15, Bluff St, Slick Rock Project #: 250144

Client:

6"

100 mm

3" 2"

50 mm

1 1/2" 1"3/4" 1/2"

10 mm

3/8"

5 mm

#4

2 mm

#10 #16

1 mm

#30

0.5 mm

#40 #100

0.10 mm

#200

P e rc e n t P a s s in g

Sieve Size

Log(x)

MH or OH

ML or OLCL -ML

0 10 20 30 40 50 60 70 80 90 100 110

P la st ic it y

In d e x

Liquid Limit

Plasticity Curve

St. George, UT 84770

This report reflects the results of the material at the location indicated on the date sampled.

This report shall not be reproduced, altered, or redistributed without written consent from Landmark Testing and Engineering

795 East Factory Drive, St. George, UT 84790 ● Phone: (435) 986-0566 ● Page 1 of 1

75 µm #200 66.2

300 µm #50 92

Diameter

D10

Coefficient of

Concavity, CC

Coefficient of

Uniformity, CU

Diameter

D60

Diameter

D30425 µm #40 96

1.18 mm #16 99

0.0 0.0

% Cobble

> 3"

% Gravel

< 3" - #4

% Sand

< #4 - #200

% Silt-Clay

< #200

33.8 66.2

2.00 mm #10 100

4.75 mm #4

9.5 mm 3/8"

19 mm 3/4"

12.5 mm 1/2"

25 mm 1" AASHTO Classification System A-4(1)

ASTM D 2487

50 mm 2" Plasticity Index 6

AASHTO M145

ASTM D 4318

37.5 mm 1-1/2" Unified Classification System CL-ML

150 mm 6" Natural Moisture Content, %

75 mm 3" Liquid Limit 22 ASTM D 4318

33.3 ASTM D 2216

Location of Sample: Test Pit 2 at 4.0' Authorized By: Client Date:

Test Standard

6/20/2025

Sieve Analysis , ASTM C136 and C117

Sieve Size % Passing

Cumulative Specification Test Result Specification

Location: St George Sampled By: M. Meyers Date: 6/20/2025

Type of Sample: Red Sandy Silty Clay Tested By: A. Pay Date: 6/30/2025

SOIL CLASSIFICATION REPORT

Date of Report: 7/15/2025

Reviewed By: Z. Girsberger

Lab#: 25SG4050

Project: Various Pole Foundations – I-15, Bluff St, Slick Rock Project #: 250144

Client:

6"

100 mm

3" 2"

50 mm

1 1/2" 1"3/4" 1/2"

10 mm

3/8"

5 mm

#4

2 mm

#10 #16

1 mm

#30

0.5 mm

#40 #100

0.10 mm

#200

P e rc e n t P a s s in g

Sieve Size

Log(x)

MH or OH

ML or OLCL -ML

0 10 20 30 40 50 60 70 80 90 100 110

P la st ic it y

In d e x

St. George, UT 84770

This report reflects the results of the material at the location indicated on the date sampled.

This report shall not be reproduced, altered, or redistributed without written consent from Landmark Testing and Engineering

795 East Factory Drive, St. George, UT 84790 ● Phone: (435) 986-0566 ● Page 1 of 1

75 µm #200 32.8

300 µm #50 58

Diameter

D10

Coefficient of

Concavity, CC

Coefficient of

Uniformity, CU

Diameter

D60

Diameter

D30425 µm #40 64

1.18 mm #16 89

0.0 1.0

% Cobble

> 3"

% Gravel

< 3" - #4

% Sand

< #4 - #200

% Silt-Clay

< #200

66.2 32.8

2.00 mm #10 97

4.75 mm #4 99

9.5 mm 3/8" 100

19 mm 3/4"

12.5 mm 1/2" 100

25 mm 1" AASHTO Classification System A-2-4(0)

ASTM D 2487

50 mm 2" Plasticity Index 8

AASHTO M145

ASTM D 4318

37.5 mm 1-1/2" Unified Classification System SC

150 mm 6" Natural Moisture Content, %

75 mm 3" Liquid Limit 27 ASTM D 4318

9.3 ASTM D 2216

Location of Sample: Test Pit 3 at 4.5' Authorized By: Client Date:

Test Standard

6/20/2025

Sieve Analysis , ASTM C136 and C117

Sieve Size % Passing

Cumulative Specification Test Result Specification

Location: St George Sampled By: M. Meyers Date: 6/20/2025

Type of Sample: Red-Brown Clayey Sand Tested By: L. May Date: 6/23/2025

SOIL CLASSIFICATION REPORT

Date of Report: 6/24/2025

Reviewed By: Z. Girsberger

Lab#: 25SG4051

Project: Various Pole Foundations – I-15, Bluff St, Slick Rock Project #: 250144

Client:

6"

100 mm

3" 2"

50 mm

1 1/2" 1"3/4" 1/2"

10 mm

3/8"

5 mm

#4

2 mm

#10 #16

1 mm

#30

0.5 mm

#40 #100

0.10 mm

#200

P e rc e n t P a s s in g

Sieve Size

Log(x)

MH or OH

ML or OLCL -ML

0 10 20 30 40 50 60 70 80 90 100 110

P la st ic it y

In d e x

St. George, UT 84770

This report reflects the results of the material at the location indicated on the date sampled.

This report shall not be reproduced, altered, or redistributed without written consent from Landmark Testing and Engineering

795 East Factory Drive, St. George, UT 84790 ● Phone: (435) 986-0566 ● Page 1 of 1

75 µm #200 50.3

300 µm #50 84

Diameter

D10

Coefficient of

Concavity, CC

Coefficient of

Uniformity, CU

Diameter

D60

Diameter

D30425 µm #40 87

1.18 mm #16 93

0.0 2.0

% Cobble

> 3"

% Gravel

< 3" - #4

% Sand

< #4 - #200

% Silt-Clay

< #200

47.7 50.3

2.00 mm #10 95

4.75 mm #4 98

9.5 mm 3/8" 100

19 mm 3/4"

12.5 mm 1/2"

25 mm 1" AASHTO Classification System A-4(0)

ASTM D 2487

50 mm 2" Plasticity Index NP

AASHTO M145

ASTM D 4318

37.5 mm 1-1/2" Unified Classification System ML

150 mm 6" Natural Moisture Content, %

75 mm 3" Liquid Limit NP ASTM D 4318

5.3 ASTM D 2216

Location of Sample: Test Pit 2 at 4.0' Authorized By: Client Date:

Test Standard

6/20/2025

Sieve Analysis , ASTM C136 and C117

Sieve Size % Passing

Cumulative Specification Test Result Specification

Location: St George Sampled By: M. Meyers Date: 6/20/2025

Type of Sample: Light Brown Sandy Silt Tested By: S. Eggleston Date: 6/23/2025

SOIL CLASSIFICATION REPORT

Date of Report: 6/23/2025

Reviewed By: Z. Girsberger

Lab#: 25SG4050

Project: Various Pole Foundations – I-15, Bluff St, Slick Rock Project #: 250144

Client:

6"

100 mm

3" 2"

50 mm

1 1/2" 1"3/4" 1/2"

10 mm

3/8"

5 mm

#4

2 mm

#10 #16

1 mm

#30

0.5 mm

#40 #100

0.10 mm

#200

P e rc e n t P a s s in g

Sieve Size

Log(x)

MH or OH

ML or OLCL -ML

0 10 20 30 40 50 60 70 80 90 100 110

P la st ic it y

In d e x

SOIL CLASSIFICATION REPORT

Date of Report: 7/15/2025

Reviewed By: Z. Girsberger

Lab#: 25SG4052

Project: Various Pole Foundations – I-15, Bluff St, Slick Rock Project #: 250144

Client:

Location: St George Sampled By: M. Meyers Date: 6/20/2025

Type of Sample: Brown Sandstone Tested By: A. Pay Date: 7/15/2025

Location of Sample: Trench 1 at 0+98' Authorized By: Client Date:

Test Standard

6/20/2025

Sieve Analysis , ASTM C136 and C117

Sieve Size % Passing

Cumulative Specification Test Result Specification

150 mm 6" Natural Moisture Content, %

75 mm 3" Liquid Limit NP ASTM D 4318

ASTM D 2216

50 mm 2" Plasticity Index NP

AASHTO M145

ASTM D 4318

37.5 mm 1-1/2" Unified Classification System

19 mm 3/4"

12.5 mm 1/2"

25 mm 1" AASHTO Classification System

ASTM D 2487

0.0 0.0

% Cobble

> 3"

% Gravel

< 3" - #4

% Sand

< #4 - #200

% Silt-Clay

< #200

0.0 0.0

2.00 mm #10

4.75 mm #4

9.5 mm 3/8"

425 µm #40

1.18 mm #16 Diameter

D10

Coefficient of

Concavity, CC

Coefficient of

Uniformity, CU

Diameter

D60

Diameter

D30

75 µm #200

300 µm #50

This report reflects the results of the material at the location indicated on the date sampled.

This report shall not be reproduced, altered, or redistributed without written consent from Landmark Testing and Engineering

795 East Factory Drive, St. George, UT 84790 ● Phone: (435) 986-0566 ● Page 1 of 1

City of St. George Energy Services

811 East Red Hills Parkway

St. George, UT 84770

6"

100 mm

3" 2"

50 mm

1 1/2" 1"3/4" 1/2"

10 mm

3/8"

5 mm

#4

2 mm

#10 #16

1 mm

#30

0.5 mm

#40 #100

0.10 mm

#200

P e rc e n t P a s s in g

Sieve Size

Log(x)

MH or OH

ML or OLCL -ML

0 10 20 30 40 50 60 70 80 90 100…