5-3-CR27006-22225510 Geotechnical Report.pdf

GEM ENGINEERING, INC. ♦ 485 North Aviation Way ♦ Cedar City, UT 84721 Phone (435) 867-6478 ♦ Fax (435) 867-4372 www.gemengineeringinc.com

GEM

Engineering, Inc.

Geotechnical Investigation

Gunlock State Park Gunlock Road

Near Gunlock, Washington, Utah

Prepared For:

Johansen & Tuttle Engineering P.O. Box 487

Castle Dale, Utah 84513

March 16, 2022

Report Number: RG2907

Copyright 2022 GEM Engineering, Inc.

All Rights Reserved http://www.gemengineeringinc.com

Gem ENGINEERING, INC.

485 North Aviation Way ♦ Cedar City, UT 84721 www.gemengineeringinc.com

RG2907 GEM ENGINEERING, INC. i

March 16, 2022

Johansen & Tuttle Engineering P.O. Box 487 Castle Dale, Utah 84513

Subject: Gunlock State Park Gunlock Road Near Gunlock, Washington, Utah

Enclosed is our geotechnical investigation report for the subject proposed campground improvements to be constructed at the subject site near Gunlock, Utah.

The report details our field exploration and laboratory testing program and presents our analysis, opinions and recommendations for the proposed project.

Moderately collapsible/compressible soils were encountered which will need to be overexcavated and recompacted as outlined in this report.

We appreciate this opportunity to be of service on this phase of the project and look forward to being of service as the project progresses. If you have any questions, please contact this office at your convenience.

Sincerely, GEM Engineering, Inc.

3/21/2022

Brennan L. Stucker, E.I.T. Joel A. Myers, P.E.

Field Engineer President

RG2907 GEM ENGINEERING, INC. ii

TABLE OF CONTENTS

Page No.

1.0 INTRODUCTION

1.1 General

1.2 Project Description

2.0 FIELD EXPLORATION

3.0 LABORATORY TESTING

4.0 SITE CONDITIONS

4.1 Surface Conditions

4.2 Subsurface Conditions

5.0 ENGINEERING ANALYSES AND RECOMMENDATIONS

5.1 General

5.2 Construction Considerations

5.2.1 Foundation Systems

5.3 Earthwork

5.3.1 Site Preparation and Grading

5.3.2 Excavations

5.3.3 Material Volume Changes

5.3.4 Structural Fill

5.4 Foundations

5.4.1 Conventional Foundations

5.5 Concrete Slabs-On-Grade

5.6 Soil Corrosion and Weathering Considerations

5.7 Moisture Protection and Drainage

5.8 Asphaltic Concrete Pavements

6.0 CLOSURE

6.1 Limitations

6.2 Additional Services

RG2907 GEM ENGINEERING, INC. iii

APPENDICES

Appendix A

Site Plan ........................................................................................... Plate 1 Trench Logs ..................................................................................... Plates 2-9 Laboratory Tests Summary ........................................................... Plate 10 Consolidation Test Results ............................................................. Plates 11-12 Unified Soils Classification Chart .................................................. Plate 13 Overexcavation, Drainage and Moisture Protection Diagram .... Plate 14

RG2907 GEM ENGINEERING, INC. Page 1

1.0 INTRODUCTION

1.1 General

This report presents the results of a geotechnical investigation performed for proposed campground improvements at Gunlock State Park on Gunlock Road near Gunlock, Washington County, Utah. The study was conducted in accordance with the client’s authorization.

The purposes of this investigation were to: (1) evaluate the general nature and engineering properties of the subsurface soils at the site; and (2) provide recommendations and opinions regarding general site grading and the design and construction of foundations, concrete slabs-on-grade and asphaltic concrete pavements. The investigation included a site reconnaissance, subsurface exploration, representative soil sampling, laboratory testing, engineering analyses, and preparation of this report.

The recommendations contained in this report are subject to the limitations presented in the "Limitations" section of the report. We recommend that all individuals reading this report read the limitations section of this document.

1.2 Project Description

We understand that a proposed campground improvements will be constructed at the location described near Gunlock, Utah. Structural loads are expected to be relatively low to moderate.

The site plan on Plate 1 shows the approximate trench locations with respect to the surrounding area.

RG2907 GEM ENGINEERING, INC. Page 2

2.0 FIELD EXPLORATION

The subsurface soil conditions were explored by excavating, 8 exploratory trenches to depths of approximately 0 to 10 feet below the existing site grade. The approximate locations of these explorations are shown on Plate 1. Soils and subsurface conditions encountered in the explorations were classified, logged and recorded at the time of excavation by our field professional. The results of the explorations are presented on the enclosed Plates 2 through 9. A key to soil symbols and terms is found on Plate 13.

RG2907 GEM ENGINEERING, INC. Page 3

3.0 LABORATORY TESTING

Representative soil samples from the explorations were tested in the laboratory to verify the field classifications and to evaluate other pertinent engineering characteristics. The soil samples were tested for solubility, Atterberg limits, maximum density and consolidation behavior. Results are presented on Plates 10 through 12.

RG2907 GEM ENGINEERING, INC. Page 4

4.0 SITE CONDITIONS

4.1 Surface Conditions

As stated previously the site is located at Gunlock State Park on Gunlock Road near

Gunlock, Washington County, Utah, as shown on Plate 1. At the time of our investigation of the proposed site it was found to have some native trees and bushes, Gunlock Reservoir and a small creek running from the reservoir towards the south along Gunlock Road. There was a general downward slope from west to east of varied steepness.

4.2 Subsurface Conditions

The on site soils encountered in the excavations generally consisted of the following:

Trench T-1 consisted of loose to dense tan, light brown to brown gravelly sand with silt which extended to the bottom of the exploratory trench approximately 10 feet below the existing site grade.

Trench T-2 consisted of loose light red brown silty sand which extended to a depth of approximately 6 feet below the existing site grade. This material was underlain by dense light red brown sandy gravel with silt which extended to the bottom of the exploratory trench approximately 10 feet below the existing site grade.

Trench T-3 consisted of dense light brown sandy gravel with silt which extended to a depth of approximately 4 feet below the existing site grade. This material was underlain by loose light brown to brown well-graded sand with silt which extended to a depth of approximately 7 feet below the existing site grade. This material was underlain by stiff light brown sandy silt which extended to the bottom of the exploratory trench approximately 10 feet below the existing site grade.

Trench T-4 was non-excavatable due to surface bedrock material.

Trench T-5 was non-excavatable due to surface bedrock and steepness of existing grade.

RG2907 GEM ENGINEERING, INC. Page 5

Trench T-6 consisted of loose light red brown poorly-graded sand with silt which extended to the bottom of the exploratory trench approximately 2 feet below the existing site grade where refusal occurred on bedrock material.

Trench T-7 consisted of very loose light red brown poorly-graded sand with silt which extended to the bottom of the exploratory trench approximately 18 inches below the existing site grade where refusal occurred on bedrock material.

Trench T-8 consisted of very loose to loose light red brown poorly-graded sand with silt which extended to the bottom of the exploratory trench approximately 5 feet below the existing site grade where refusal occurred on bedrock material. Pinhole voids were observed throughout much of exploratory trenches.

Numerous factors contribute to fluctuations in groundwater levels and locations. The evaluation of these factors was beyond the scope of this study. Groundwater was encountered at a depth of 9 feet below existing site grade in exploaration T-1. The soils were in a slightly moist to wet condition throughout the depths explored.

The encountered subsurface conditions are described in detail on the enclosed trench logs, Plates 2 through 9. Due to the nature and depositional characteristics of the native soils, care should be taken in extrapolating subsurface conditions beyond the exploration loctations.

The laboratory tests results indicated that the on-site soils exhibited a relatively low solubility, low plasticity and a low to moderate collapse potential.

RG2907 GEM ENGINEERING, INC. Page 6

5.0 ENGINEERING ANALYSIS AND RECOMMENDATIONS

5.1 General

Based on our investigation there are loose, soft and/or collapsible soils located at the site which will require stabilization and/or overexcavation prior to the placement of structural fill. However, it is our opinion that the subject site is suitable for the proposed construction provided that the recommendations contained in this report are followed.

The following sections of this report present our recommendations to reduce the potential for structural damage. They contain specific opinions and recommendations concerning construction considerations, site preparation and grading, structural fill, foundation design, retaining walls, concrete slabs-on-grade, soil corrosion, moisture protection and structural pavement sections.

One of the most critical recommendations to follow in order to reduce potential for structural damage is to set the finished floor slab elevations high enough to facilitate proper drainage away from the structure.

5.2 Construction Considerations

5.2.1 Foundation Systems

After overexcavation and recompaction are completed, the structures can be supported by conventional strip and/or spread footings founded on properly placed and compacted structural fill or competent bedrock. However, building footings shall not be founded on a combination of both structural fill and bedrock. Refer to section 5.3.1 for additional information.

RG2907 GEM ENGINEERING, INC. Page 7

5.3 Earthwork

5.3.1 Site Preparation and Grading

Within the areas to be graded, existing vegetation, loose soils, and debris, should be removed and hauled off the site. Any undocumented fill soils, and soft, loose, collapsible and/or disturbed native soils should be excavated to expose competent, dense or medium dense native soils.

Based upon soil types and laboratory consolidation tests, the required depth of overexcavation is as follows: A minimum of 2 feet below the bottom of footing elevation or 2 feet below the existing site grade, whichever is greater.

Overexcavations should extend laterally beyond the edges of the footing, at each side, at least a distance equal to the depth of overexcavation. In no case shall the total width of excavtion be less than the footing width plus 2 times the depth of overexcavation. (width of O.X. + ftg width + width of O.X.)

Foundations should not be founded on a combination of structural fill and bedrock.

It is anticipated that bedrock will be encountered at depths of 0 to 5 feet below existing grade in most areas of the site. If bedrock is encountered at footing depth one of two options shall be implemented. Option 1, the entire building site can be excavated down to bedrock so that all foundations for the building are sitting on competent bedrock. Option 2, the bedrock can be overexcavated 12 inches and then the grade raised back up with structural fill so that the entire building is sitting on a minimum of 12 inches of structural fill.

Slabs-on-grade, exterior concrete flatwork, and pavements should be supported by a zone of properly placed and compacted structural fill. Overexcavations on the order of 12 inches below the supportive gravel layer or 12 inches below the existing site grade, whichever is greater, are required. As an alternative to the above, 8 inches of Type 1 pit run gravel can be substituted for the 12 inches of recompacted

RG2907 GEM ENGINEERING, INC. Page 8 native soils. Excavations shall extend laterally at least 2 feet beyond exterior flatwork and pavement areas.

If loose soft or pumping soils are encountered at the bottom of the overexcavations, stabilization and/or additional overexcavation will be required prior to the placement of structural fill. Overexcavations may be terminated if competent, medium-dense granular soils or competent bedrock material are encountered.

A GEM Engineering representative should observe excavation and determine if it is acceptable to terminate the excavation or reduce the overexcavation depth.

The majority of on-site soils, free of organics and debris, should be suitable for reuse as structural fill. If using on-site soils for backfill or structural fill a shrinkage factor of up to 20 percent can be expected.

Following excavation of the unsuitable soils as described above, a representative of this office should observe the excavation bottoms prior to the continuance of grading to verify that unsuitable materials have been removed and that competent soils have been exposed. The native soils exposed after overexcavation should be scarified to a depth of 6 inches and brought to within 2 percent of the optimum moisture content for granular soils and slightly above optimum for fine-grained soils. Soil shall then be compacted to at least 90 percent of the maximum dry density for granular soils and 85 percent of the maximum dry density for fine grained soils as determined by ASTM D1557. The site should then be brought to the proper grade with structural fill as described in the Structural Fill section.

Subgrade materials supporting slabs-on-grade, exterior concrete flatwork, and pavements should be kept moist and not be allowed to dry out and crack. If the subgrade has been disturbed or dried out prior to placement of aggregate base, the exposed soils should be moisture-conditioned and recompacted as outlined in the

Structural Fill section of this report.

RG2907 GEM ENGINEERING, INC. Page 9

We recommend that a GEM Engineering representative be allowed to review the grading plans when prepared to evaluate their compatibility with the recommendations of this report.

5.3.2 Excavations

The majority of the soils encountered in our explorations should be excavatable with conventional earthwork equipment. It is also possible that soft pumping soils may be encountered. Pumping soils will need to be stabilized prior to placing of structural fill. Safety of construction personnel is the responsibility of the

Contractor.

5.3.3 Material Volume Changes

There will be shrinkage losses when excavating and compacting the on-site soils.

An estimated average shrinkage factor of 20 percent is applicable for the loose to medium-dense near-surface native soils. A subsidence factor of 0.1 should be used in all areas where the surficial soils are scarified and recompacted to a depth of 6 inches.

5.3.4 Structural Fill

All fill placed for the support of slabs-on-grade, exterior concrete flatwork, and pavements should be structural fill. Structural fill may consist of approved excavated on-site or imported fill materials. Structural fill should have a swell potential less than 4 percent under a 60 psf surcharge, have a solubility of less than

3 percent, be free of organics, salts, or inert materials larger than 4 inches nominal size, and be similar in gradation to the on-site soils.

Structural fill should be placed in maximum eight-inch loose lifts and compacted on a horizontal plane, unless otherwise approved by the Geotechnical Engineer.

Soils in compacted fills should be compacted to at least 90 percent of the maximum dry density as determined by ASTM D1557 for fine grained soils and 95 percent

RG2907 GEM ENGINEERING, INC. Page 10 for granular soils. The moisture content should be within 2 percent of optimum for granular soils and at least 2 percent above optimum for fine-grained soils. Any imported fill materials should be approved prior to importing. Also, prior to placing any fill, the excavations should be observed by a GEM Engineering representative to observe that unsuitable materials have been removed.

Structural fill shall be tested for minimum density compliance by means of a moisture-density gauge in accordance with ASTM D6938 or other approved methods. Moisture-density testing shall be performed at the bottom of overexcavation and every 12 inches vertically until the bottom of footing is reached.

Backfill material surrounding basement walls and stem walls moisture-density testing shall be performed beginning at the bottom of footing elevation and continue at intervals of 24 inches vertically until finished grade is reached.

5.4 Foundations

5.4.1 Conventional Foundations

General: Conventional shallow foundations consisting of strip and/or spread footings can be utilized for the support of the proposed building provided that overexcavation is completed in accordance with the requirements and recommendations of this report as described in the Earthwork section.

For frost protection the bottom of exterior conventional spread and strip footings shall be at least 30 inches below the lowest adjacent final compacted subgrade.

Foundations for structures constructed on soils, prepared in accordance with the recommendations and requirements of this report, may be designed for an allowable net bearing pressure of 2000 psf. This bearing pressure may be increased by one-third for load combinations containing seismic or wind loads.

RG2907 GEM ENGINEERING, INC. Page 11

Prior to constructing the foundations, the footing excavations should be observed by a GEM Engineering representative to confirm that the soil preparation has been completed in accordance with the requirements and recommendations of this report.

Seismicity: The following seismic design values, in accordance with the requirements of the 2018 International Building Code (IBC), shall be used for the design of structures at the site:

Soil site class = D

Ground motion coefficient for 0.2 second period Ss = 0.468

Ground motion coefficient for 1.0 second period S1 = 0.151

Site amplification factor at 0.2 second Fa = 1.425

Site amplification factor at 1.0 second Fv = 2.297

Peak ground acceleration PGA = 0.206

Seismic Design Category SDC = D

Seismic response coefficient Cs = (See note 1)

Note 1: A site-specific ground motion hazard analysis was NOT completed for this location. Therefore, in accordance with ASCE 7-16 section 11.4.8 Exception 2, the seismic response coefficient Cs shall be determined by Eq (12.8-2) for values of T ≤ 1.5 Ts and taken as equal to 1.5 times the value computed in accordance with either Eq. (12.8-3) for TL ≥ T > 1.5 Ts or Eq. (12.8-4) for T > TL.

It is the opinion of GEM Engineering, Inc. that based on the soils encountered at the exploratory excavations and the ground water depth the potential for liquefaction at this site is low.

Settlement: Foundations established in accordance with the recommendations and requirements of this report are estimated to be subject to 1 ½” or less of settlement if the soils beneath the overexcavation do not become moistened. Estimated differential settlement could be on the order of ½ the total settlement.

RG2907 GEM ENGINEERING, INC. Page 12

Lateral Earth Pressures: The following lateral earth pressure equivalent fluid densities shall be used in the design of the structure.

Properly Compacted On-Site Soils

Active Pressure 32 pcf

At Rest Pressure 49 pcf

Passive Pressure 260 pcf

Equivalent fluid densities presented above assume that there will be no build-up of hydrostatic pressure. Any surcharge from adjacent structures or traffic loads should be added to this pressure. When passive pressure is used for resistance to lateral loads the top one foot of soil should be neglected. The maximum allowable passive pressure for lateral load resistance should not exceed 1,600 psf.

The seismic lateral earth pressure coefficient (kh) is 0.10.

Lateral Load Resistance: Horizontal loads acting on foundations will be resisted by friction acting at the base of foundations and/or passive earth pressures acting against the side of footings and concrete walls. If design makes use of passive earth pressures, it is important that a GEM Engineering representative be present during backfill placement.

The friction force acting along the base of footings founded on suitable foundation soils may be calculated using a coefficient of friction of 0.40.

Lateral loads acting on buried utility lines may be resisted by thrust blocks reacting against undisturbed native soil or properly placed and compacted structural fill. The passive lateral earth pressure equivalent fluid density and coefficient of friction, previously listed, may be used for thrust block design.

RG2907 GEM ENGINEERING, INC. Page 13

5.5 Concrete Slabs-On-Grade

Satisfactory support for concrete slabs-on-grade and exterior concrete flatwork may be provided by a 6 inch layer of compacted gravel overlying properly placed and compacted structural fill as recommended in the Site Grading section of this report. The layer of compacted gravel may consist of road base or pit-run gravel with a 2-inch maximum particle size and not more than 12% fines passing the No. 200 sieve. The gravel layer should be compacted to at least 95% of the maximum dry density as determined by ASTM

D1557.

All concrete slabs should be designed to minimize cracking as a result of shrinkage.

Reinforcement requirements shall be provided by the Structural Engineer. Reinforcement should be installed at the mid-height of the slab unless directed otherwise by the Structural

Engineer.

Special precautions must be taken during the placement and curing of all concrete slabs.

Excessive slump (high water-cement ratio) of the concrete and/or improper curing procedures used during either hot or cold weather conditions could lead to excessive shrinkage, cracking or curling in the slabs. All concrete placement and curing operations shall be performed in accordance with the American Concrete Institute (ACI) Manual.

5.6 Soil Corrosion and Weathering Considerations

Based on similar studies performed in the area, the on-site soils contain salts in sufficient concentration to be considered corrosive to both concrete and metal. Therefore, all concrete in contact with the on-site soils and used in stem walls should contain Type V or equivalent sulfate-resistant cement, and should be placed with a maximum four inch slump.

Furthermore concrete shall meet requirements specified in Tables 19.3.1.1 & 19.3.2.1 of

ACI 318-14 for severe sulfate exposure. Special protection to buried metal pipes and water lines should be considered for long term performance of these underground utilities.

Consideration should be given to cathodic protection of buried metal pipes, or to the use of PVC pipe where permitted by local building codes.

RG2907 GEM ENGINEERING, INC. Page 14

5.7 Moisture Protection and Drainage

It is imperative that precautions are taken during and after construction to eliminate, or at least minimize, wetting of foundation soils. Drainage and grading shall be constructed in accordance with the requirements of section 1804.4 of the 2018 International Building

Code (IBC). Positive drainage shall be established away from the exterior walls of the structure. The required minimum slope is five percent (5%) in landscape areas and two percent (2%) in pavement areas, for a minimum distance of 10 feet from the structure. Roof runoff and other sources of moisture should not be allowed to infiltrate the soils in the vicinity of, or upslope from, the structure. No roof moisture should infiltrate the soils beneath the foundations.

All utility trenches leading into the structures should be backfilled with compacted non-pervious fill. Special care should be taken during installation of sub floor sewer and water lines to reduce the possibility of future subsurface saturation.

Landscape watering adjacent to the structure should be eliminated. As an additional protection a concrete slab could be placed around the structure to facilitate drainage away from the structure as described above. Any planters adjacent to the structure should have sealed bottoms. It is recommended that desert landscaping techniques be utilized.

5.8 Asphaltic Concrete Pavements

Asphaltic concrete pavement sections were developed for non-dedicated areas. In developing our recommendations, we have assumed that: (1) a minimum of 6 inches of

Type 1 gravel (3-inch minus pit run) will be provided beneath the pavement section; (2) a

Traffic Index value of 6.5 for automobile traffic and parking areas is appropriate; and (3) an R-value of 65 is representative of recompacted native soils. The following table presents the minimum recommended structural pavement sections:

RG2907 GEM ENGINEERING, INC. Page 15

Asphaltic Concrete Pavements

Traffic Condition

Assumed Traffic Index

(T.I.)

Asphalt Thickness

(in)

Road Base Thickness

(in)

Compacted Type 1 Gravel

(in)

Light

Traffic/Parking

6.5 3 6 10

Asphalt and aggregate base material should conform to local requirements. All base material should be compacted to at least (95%) of the maximum dry density (ASTM

D1557). Asphalt should be compacted to minimum of (96%) of the Marshall maximum density. Asphaltic concrete and base materials should be tested prior to delivery to the site and during placement to determine conformance with the project specifications.

It is important that parking area grades be set to provide positive drainage to suitable drainage structures. A desirable slope for drainage in paved areas is two percent.

RG2907 GEM ENGINEERING, INC. Page 16

6.0 CLOSURE

6.1 Limitations

The recommendations contained in this report are based on the field exploration, laboratory tests, and our understanding of the proposed construction. The subsurface data used in the preparation of this report were obtained from the exploration made during this investigation. It is possible that variations in the soil and groundwater conditions could exist elsewhere on the site. The nature and extent of variations may not be evident until construction occurs. If any conditions are encountered at the site which are different from those described in this report, GEM Engineering should be immediately notified so that we may make any necessary revisions to recommendations contained in this report. In addition, if the scope of the proposed construction changes from that described in this report, GEM Engineering should likewise be notified.

This report was prepared in accordance with the generally accepted standard of practice at the time the report was written. Although some potential geologic hazards may be identified in this Geotechnical Investigation Report, this is NOT a Geologic Hazards

Report and should not be regarded as such. No warranty, express or implied, is made. It is the Client's responsibility to see that all parties to the project, including the Designer, Contractor, Subcontractors, etc., are made aware of this report in its entirety. The use of information contained in this report for bidding purposes should be done at the Contractor's option and risk. GEM Engineering will not accept the responsibility for damage caused by the uncontrolled action of water at the site.

6.2 Additional Services

The recommendations made in this report are based on the assumption that an adequate program of tests and observations will be made during the construction to verify compliance with the recommendations. These tests and observations should include, but not necessarily be limited to, the following:

RG2907 GEM ENGINEERING, INC. Page 17

• Observations and testing during site preparation, earthwork and structural fill placement

• Observations of footing excavations

• Consultation as may be required during construction

We also recommend that project plans and specifications be reviewed by us to verify compatibility with our conclusions and recommendations. Additional information concerning the scope and cost of these services can be obtained from our office.

GEM ENGINEERING, INC.

Appendix A

SITE PLAN

Plate:Gunlock Road, Gunlock, Utah Client: Johansen & Tuttle Engineering 1 Report No: RG2907 ENGINEERING, INC.

PROJECT: Gunlock State Park

GEM

Notes:

Key: Approximate Trench Location Plan Not to Scale

N

T-1

T-3

T-2

T-4

T-5

T-6

T-7

T-8 Gunlock Reservoir

Trench No. 1 Sheet 1 of 1 D ep th

(f t)

S am pl e

U

SC

S Sy m bo l 2

SW

SM

SW

SM

SW

SM

SW

SM

SW

SM

SW

SM

SW

SM

SW

SM

SW

SM

SW

SM

Sample: Drive Sample Bag Sample Bucket Sample

1)

2) 13

3)

5)

TRENCH LOG

Location: See Site Plan Elevation: Not Measured Date

Excavated:

2/21/2022

T es ts 1 Soil Description

(Additional comments below)

C ol or

R el at ive

M oi st ur e

D en sit y

C em en ta tio n

M ax s ize

P ar tic le

Sol, P - Gravelly Sand with Silt Light Brown SM L At, M to

Tan

-- CG

- Pinhole Voids to

Brown

D C

- Groundwater encountered

Bottom @ 10'

W = Weak cementation, M = Moderate cementation, S = Strong cementation None noted

At = Atterberg, M = Moisture, Sol = Solubility, E = Expansion, C = Consol, P = Proctor, CS =Coarse Sieve Notes:

See Plate for explanation of Unified Soil Classification System Groundwater:

D = Dry, SM = Slightly Moist, M = Moist, VM = Very Moist, W = Wet Encountered at 9'

ENGINEERING, INC.

W

Gunlock State Park PROJECT: GEM Plate:Gunlock Road, Gunlock, Utah Client: Johansen & Tuttle Engineering 2 Report No: RG2907

6) B=Boulder, C= Cobble, CG=Coarse Gravel (3" - 3/4"), FG=Fine Gravel (3/4" - 1/4"), CS=Coarse Sand (#10-#4), MS=Medium Sand (#40 - #10), FS=Fine Sand (#200 - #40), F=Fines

4) Coarse Grain: VL = Very Loose, L = Loose, MD = Medium Dense, D = Dense, VD = Very Dense Fine Grain: VSF = Very Soft, SF = Soft, MS = Medium Stiff, S = Stiff, VS = Very Stiff, H = Hard Caving of side walls:

Trench No. 2 Sheet 1 of 1 ep th

(f t)

S am pl e

U

SC

S Sy m bo l 2

GW

GM

GW

GM

GW

GM

GW

GM

Sample: Drive Sample Bag Sample Bucket Sample

1)

2) 13

3)

5)

TRENCH LOG

Location: See Site Plan Elevation: Not Measured Date

Excavated:

2/21/2022

T es ts 1 Soil Description

(Additional comments below)

C ol or

R el at ive

M oi st ur e

D en sit y

C em en ta tio n

M ax s ize

P ar

- Silty Sand Light SM L -- MS

Sol, C At, M

- Pinhole Voids Red Brown

P

- Sandy Gravel with Silt Light SM D -- C

Red Brown

Bottom @ 10'

None noted

At = Atterberg, M = Moisture, Sol = Solubility, E = Expansion, C = Consol, P = Proctor, CS =Coarse Sieve Notes:

See Plate for explanation of Unified Soil Classification System Groundwater:

D = Dry, SM = Slightly Moist, M = Moist, VM = Very Moist, W = Wet Not encountered

ENGINEERING, INC.

SM

Gunlock State Park PROJECT: GEM Plate:Gunlock Road, Gunlock, Utah Client: Johansen & Tuttle Engineering 3 Report No: RG2907

6) B=Boulder, C= Cobble, CG=Coarse Gravel (3" - 3/4"), FG=Fine Gravel (3/4" - 1/4"), CS=Coarse Sand (#10-#4), MS=Medium Sand (#40 - #10), FS=Fine Sand (#200 - #40), F=Fines

4) Coarse Grain: VL = Very Loose, L = Loose, MD = Medium Dense, D = Dense, VD = Very Dense Fine Grain: VSF = Very Soft, SF = Soft, MS = Medium Stiff, S = Stiff, VS = Very Stiff, H = Hard Caving of side walls:

W = Weak cementation, M = Moderate cementation, S = Strong cementation

Trench No. 3 Sheet 1 of 1 ep th

(f t)

S am pl e

U

SC

S Sy m bo l 2

GW

GM

GW

GM

GW

GM

GW

GM

Sample: Drive Sample Bag Sample Bucket Sample

1)

2) 13

3)

5)

TRENCH LOG

Location: See Site Plan Elevation: Not Measured Date

Excavated:

2/21/2022

T es ts 1 Soil Description

(Additional comments below)

C ol or

R el at ive

M oi st ur e

D en sit y

C em en ta tio n

M ax s ize

P ar

At, M - Sandy Gravel with Silt Light Brown SM D -- B Sol, P

5 Light Brown SM

CG

At, M - Pinhole Voids Brown M

- Well-Graded Sand with Gravel to to L --

Sol, P

Sol

CS

At, M - Pinhole Voids

- Sandy Silt Light Brown SM S --

Bottom @ 10'

Plate:Gunlock Road, Gunlock, Utah Client: Johansen & Tuttle Engineering 4 Report No: RG2907

6) B=Boulder, C= Cobble, CG=Coarse Gravel (3" - 3/4"), FG=Fine Gravel (3/4" - 1/4"), CS=Coarse Sand (#10-#4), MS=Medium Sand (#40 - #10), FS=Fine Sand (#200 - #40), F=Fines

ENGINEERING, INC.

SW

ML

Gunlock State Park PROJECT: GEM

4) Coarse Grain: VL = Very Loose, L = Loose, MD = Medium Dense, D = Dense, VD = Very Dense Fine Grain: VSF = Very Soft, SF = Soft, MS = Medium Stiff, S = Stiff, VS = Very Stiff, H = Hard Caving of side walls:

W = Weak cementation, M = Moderate cementation, S = Strong cementation None noted

At = Atterberg, M = Moisture, Sol = Solubility, E = Expansion, C = Consol, P = Proctor, CS =Coarse Sieve Notes:

See Plate for explanation of Unified Soil Classification System Groundwater:

D = Dry, SM = Slightly Moist, M = Moist, VM = Very Moist, W = Wet Not encountered

Trench No. 4 Sheet 1 of 1 ep th

(f t)

S am pl e

U

SC

S Sy m bo l 2

Sample: Drive Sample Bag Sample Bucket Sample

1)

2) 13

3)

5)

TRENCH LOG

Location: See Site Plan Elevation: Not Measured Date

Excavated:

2/21/2022

T es ts 1 Soil Description

(Additional comments below)

C ol or

R el at ive

M oi st ur e

D en sit y

C em en ta tio n

M ax s ize

P ar

Exposed Sandtone Bedrock at Surface

At = Atterberg, M = Moisture, Sol = Solubility, E = Expansion, C = Consol, P = Proctor, CS =Coarse Sieve Notes:

See Plate for explanation of Unified Soil Classification System Groundwater:

D = Dry, SM = Slightly Moist, M = Moist, VM = Very Moist, W = Wet Not encountered

6) B=Boulder, C= Cobble, CG=Coarse Gravel (3" - 3/4"), FG=Fine Gravel (3/4" - 1/4"), CS=Coarse Sand (#10-#4), MS=Medium Sand (#40 - #10), FS=Fine Sand (#200 - #40), F=Fines

4) Coarse Grain: VL = Very Loose, L = Loose, MD = Medium Dense, D = Dense, VD = Very Dense Fine Grain: VSF = Very Soft, SF = Soft, MS = Medium Stiff, S = Stiff, VS = Very Stiff, H = Hard Caving of side walls:

W = Weak cementation, M = Moderate cementation, S = Strong cementation None noted

ENGINEERING, INC.

Gunlock State Park PROJECT: GEM Plate:Gunlock Road, Gunlock, Utah Client: Johansen & Tuttle Engineering 5 Report No: RG2907

Trench No. 5 Sheet 1 of 1 ep th

(f t)

S am pl e

U

SC

S Sy m bo l 2

Sample: Drive Sample Bag Sample Bucket Sample

1)

2) 13

3)

5)

TRENCH LOG

Location: See Site Plan Elevation: Not Measured Date

Excavated:

2/21/2022

T es ts 1 Soil Description

(Additional comments below)

C ol or

R el at ive

M oi st ur e

D en sit y

C em en ta tio n

M ax s ize

P ar

Exposed Sandstone Bedrock at Surface

At = Atterberg, M = Moisture, Sol = Solubility, E = Expansion, C = Consol, P = Proctor, CS =Coarse Sieve Notes:

See Plate for explanation of Unified Soil Classification System Groundwater:

D = Dry, SM = Slightly Moist, M = Moist, VM = Very Moist, W = Wet Not encountered

6) B=Boulder, C= Cobble, CG=Coarse Gravel (3" - 3/4"), FG=Fine Gravel (3/4" - 1/4"), CS=Coarse Sand (#10-#4), MS=Medium Sand (#40 - #10), FS=Fine Sand (#200 - #40), F=Fines

4) Coarse Grain: VL = Very Loose, L = Loose, MD = Medium Dense, D = Dense, VD = Very Dense Fine Grain: VSF = Very Soft, SF = Soft, MS = Medium Stiff, S = Stiff, VS = Very Stiff, H = Hard Caving of side walls:

W = Weak cementation, M = Moderate cementation, S = Strong cementation None noted

ENGINEERING, INC.

Client: Johansen & Tuttle Engineering 6 Report No: RG2907

Trench No. 6 Sheet 1 of 1 ep th

(f t)

S am pl e

U

SC

S Sy m bo l 2

SP

SM

SP

SM

Sample: Drive Sample Bag Sample Bucket Sample

1)

2) 13

3)

5)

TRENCH LOG

Location: See Site Plan Elevation: Not Measured Date

Excavated:

2/21/2022

T es ts 1 Soil Description

(Additional comments below)

C ol or

R el at ive

M oi st ur e

D en sit y

C em en ta tio n

M ax s ize

P ar

At, M - Poorly-Graded Sand with Silt Light SM L -- FG Sol - Pinhole Voids Red Brown

Bedrock Material @ 2'

None noted

At = Atterberg, M = Moisture, Sol = Solubility, E = Expansion, C = Consol, P = Proctor, CS =Coarse Sieve Notes:

See Plate for explanation of Unified Soil Classification System Groundwater:

D = Dry, SM = Slightly Moist, M = Moist, VM = Very Moist, W = Wet Not encountered

ENGINEERING, INC.

Gunlock State Park PROJECT: GEM Plate:Gunlock Road, Gunlock, Utah Client: Johansen & Tuttle Engineering 7 Report No: RG2907

6) B=Boulder, C= Cobble, CG=Coarse Gravel (3" - 3/4"), FG=Fine Gravel (3/4" - 1/4"), CS=Coarse Sand (#10-#4), MS=Medium Sand (#40 - #10), FS=Fine Sand (#200 - #40), F=Fines

4) Coarse Grain: VL = Very Loose, L = Loose, MD = Medium Dense, D = Dense, VD = Very Dense Fine Grain: VSF = Very Soft, SF = Soft, MS = Medium Stiff, S = Stiff, VS = Very Stiff, H = Hard Caving of side walls:

W = Weak cementation, M = Moderate cementation, S = Strong cementation

Trench No. 7 Sheet 1 of 1 ep th

(f t)

S am pl e

U

SC

S Sy m bo l 2

SP

SM

SP

Sample: Drive Sample Bag Sample Bucket Sample

1)

2) 13

3)

5)

TRENCH LOG

Location: See Site Plan Elevation: Not Measured Date

Excavated:

2/21/2022

T es ts 1 Soil Description

(Additional comments below)

C ol or

R el at ive

M oi st ur e

D en sit y

C em en ta tio n

M ax s ize

P ar

- Poorly-Graded Sand with Silt Light SM VL -- FG

Bedrock Material @ 18"

- Pinhole Voids Red Brown

At = Atterberg, M = Moisture, Sol = Solubility, E = Expansion, C = Consol, P = Proctor, CS =Coarse Sieve Notes:

See Plate for explanation of Unified Soil Classification System Groundwater:

D = Dry, SM = Slightly Moist, M = Moist, VM = Very Moist, W = Wet Not encountered

6) B=Boulder, C= Cobble, CG=Coarse Gravel (3" - 3/4"), FG=Fine Gravel (3/4" - 1/4"), CS=Coarse Sand (#10-#4), MS=Medium Sand (#40 - #10), FS=Fine Sand (#200 - #40), F=Fines

4) Coarse Grain: VL = Very Loose, L = Loose, MD = Medium Dense, D = Dense, VD = Very Dense Fine Grain: VSF = Very Soft, SF = Soft, MS = Medium Stiff, S = Stiff, VS = Very Stiff, H = Hard Caving of side walls:

W = Weak cementation, M = Moderate cementation, S = Strong cementation None noted

ENGINEERING, INC.

Client: Johansen & Tuttle Engineering 8 Report No: RG2907

Trench No. 8 Sheet 1 of 1 ep th

(f t)

S am pl e

U

SC

S Sy m bo l 2

SP

SM

SP

SM

SP

SM

SP

SM

SP

SM

Sample: Drive Sample Bag Sample Bucket Sample

1)

2) 13

3)

5)

TRENCH LOG

Location: See Site Plan Elevation: Not Measured Date

Excavated:

2/21/2022

T es ts 1 Soil Description

(Additional comments below)

C ol or

R el at ive

M oi st ur e

D en sit y

C em en ta tio n

M ax s ize

P ar

VL

FG

At, M - Pinhole Voids Red Brown L

- Poorly-Graded Sand with Silt Light SM to --

Sol, C

Bedrock Material @ 5'

At = Atterberg, M = Moisture, Sol = Solubility, E = Expansion, C = Consol, P = Proctor, CS =Coarse Sieve Notes:

See Plate for explanation of Unified Soil Classification System Groundwater:

D = Dry, SM = Slightly Moist, M = Moist, VM = Very Moist, W = Wet Not encountered

6) B=Boulder, C= Cobble, CG=Coarse Gravel (3" - 3/4"), FG=Fine Gravel (3/4" - 1/4"), CS=Coarse Sand (#10-#4), MS=Medium Sand (#40 - #10), FS=Fine Sand (#200 - #40), F=Fines

4) Coarse Grain: VL = Very Loose, L = Loose, MD = Medium Dense, D = Dense, VD = Very Dense Fine Grain: VSF = Very Soft, SF = Soft, MS = Medium Stiff, S = Stiff, VS = Very Stiff, H = Hard Caving of side walls:

W = Weak cementation, M = Moderate cementation, S = Strong cementation None noted

ENGINEERING, INC.

Client: Johansen & Tuttle Engineering 9 Report No: RG2907

SW SM

GW GM

SP SM

SP SM

Key:

LABORATORY TESTS SUMMARY Sheet

T re nc h

B or in g No

S am pl e

D ep th (f t)

U

CS

C S ym bo l Soil Description

F ie ld

M oi st ur e

F ie ld D ry D en sit y (p cf

So lu bi lit y

) Fine Sieve Atterberg Limits Expansion Net Percent Consolidation

Modified Proctor

% Passing

L iq ui d

L im it

P la st ic

L im it

P la st ici ty In de x

L oa d

4.1 --lb

H lb

D ry

D en sit y

Op tim um M oi st ur e

#4 #10 #40 #200

121.0 9.0

T-2 4' SM Silty Sand 3.0 90.4 0.5

NP NP -- -- -- --<0.1 73.6 62.9 39.9 6.9 NPT-1 4' Gravelly Sand with Silt

11.5

T-3 2' Sandy Gravel with Silt 4.0 -- 0.1 40.3

NP -- -- 0.4 2.6 113.0100.0 100.0 98.1 17.9 NP NP

-- -- -- -- 127.0 7.534.6 25.3 5.4 NP NP NP

T-3 6' SW Well-Graded Sand with Gravel 2.7 -- <0.1 77.4 37.2

12.4 --

-- -- -- 120.5 9.06.3 0.8 NP NP NP --

T-6 1' Poorly-Graded Sand with Silt 4.3 -- 0.1

NP NP -- -- -- --0.2 100.0 99.1 95.3 61.0 NPT-3 9' ML Sandy Silt

T-8 3' Poorly-Graded Sand with Silt 4.5 101.3 0.1 97.9

NP -- -- -- -- --98.4 98.1 97.5 6.7 NP NP

-- -- 0.3 1.7 -- --97.2 96.4 7.4 NP NP NP

Johansen & Tuttle Engineering 10 Report No: RG2907 ENGINEERING, INC.

Notes: Gunlock State Park PROJECT: GEM Plate:NP = Non Plastic, -- indicates no test performed Gunlock Road, Gunlock, Utah Atterberg Limits are for classification of fine-grained and fine-grained fraction of coarse-grained soils

Client:

CONSOLIDATION TEST DATA

Sample Location - T-2 4' Water added at 1000 psf

Load (psf) Percent Consolidation

Net Percent Consolidation *

500 0.87 0.00

1000 1.31 0.44

1000 + H20 2.30 1.43

2000 3.42 2.55

4000 4.35 3.48

500 3.96 3.09

Net consolidation assumes that existing native pressure on soil is aproximately equal to 500 psf

Gunlock State Park

GEM Plate:Gunlock Road, Gunlock, Utah Client: Johansen & Tuttle Engineering 11 Report No: RG2907 ENGINEERING, INC.

PROJECT:

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

5.00

100 1000 10000

Pe rc en t C on so lid at io n

Load (psf)

CONSOLIDATION TEST DATA

Sample Location - T-8 3' Water added at 1000 psf

Load (psf) Percent Consolidation

Net Percent Consolidation *

500 0.41 0.00

1000 0.70 0.29

1000 + H20 1.32 0.91

2000 2.10 1.69

4000 2.67 2.26

500 2.37 1.96

Net consolidation assumes that existing native pressure on soil is aproximately equal to 500 psf

Gunlock State Park

GEM Plate:Gunlock Road, Gunlock, Utah Client: Johansen & Tuttle Engineering 12 Report No: RG2907 ENGINEERING, INC.

PROJECT:

0.00

0.50

1.00

1.50

2.00

2.50

3.00

100 1000 10000

Pe rc en t C on so lid at io n

Load (psf)

COARSE

GRAINED SOILS

50% or more is retained (larger than) the No. 200 sieve.

Gravels Clean Gravels GW

THE UNIFIED SOIL CLASSIFICATION SYSTEM (USCS)

Major Division Symbol Color Typical Group Names

Well graded gravels, gravel sand mixtures, little or no fines

More than 50 % of coarse part is larger than the No. 4 sieve.

Less than 5% fines GP Poorly graded gravels/gravel sand mixtures

Gravels with Fines GM Silty gravels, gravel-sand-silt mixtures

Sands Clean Sands SW Well graded sands, gravely sands, little or no fines

SM Silty sands, sand-silt mixtures

More than 12% fines

More than 12% fines GC Clayey gravels, gravel-clay-sand mixtures

SC Clayey sands, sand clay mixtures

FINE GRAINED

SOILS

50% or more passes (smaller than) the No.

200 sieve.

Silts and Clays Liquid Limit less than 50

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

CL-ML

More than 50 % of coarse part is smaller than the No. 4 sieve.

Less than 5% fines SP Poorly graded sands or gravely sands, little or no fines

Sands w/ Fines

Inorganic clay-silt mixture and very fine sand, silty or clayey fine sands or clayey silts with low plasticity.

CL Inorganic clays of low to medium plasticity, gravely clays, sandy clays, silty clays, lean clays

OL Organic silts and organic silty clays of low plasticity

Silts and Clays Liquid Limit 50 or more

MH Inorganic silts, micaceous or diatomaceous fine sandy or silty soils, elastic silts

CH Inorganic clays of high plasticity, fat clays

OH Organic clays or medium to high plasticity, organic silts

Highly Organic Soils PT Peat and other highly organic silts

PLASTICITY CHART

RG2907 ENGINEERING, INC.

Gunlock State Park PROJECT: GEM Plate:Gunlock Road, Gunlock, Utah Client: Johansen & Tuttle Engineering 13 Report No:

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

Pl as tic ity

I nd ex

PI

Liquid Limit (LL)

CL-ML

ML

ML or OL

MH or OH

CH

CL

"A" Line

The width of overexcavation is equal to 5ft past the edge of ftg or equal to the depth of overexcavtion which is

GREATER.

OVEREXCAVATION, DRAINAGE AND

MOISTURE PROTECTION DIAGRAM

Basement Foundation The depth of overexcavation shall extend from the bottom of the footing or existing site grade whichever is

GREATER.

In some casses GEM Engineering may approve a width of lateral overexcavation less than 5'-0" but it shall never be less than the required depth of overexcavation.

The total width of overexcavation is euqal to the width of the footing plus 2x the width of lateral overexcavation.

Drainage and gradation shall be constructed in accordance with the requirements of section R401.3 & R801.3 of the 2018 IRC or section 1804.4 of the 2018 IBC. Refer to geotechnical report for additional drainage & grading requirements & recommendations.

Slab-On-Grade Foundation Refer to section 5.3.4 for moisture-density testing requirements.

ENGINEERING, INC.

PROJECT: Gunlock State Park

GEM Plate:Gunlock Road, Gunlock, Utah Client: Johansen & Tuttle Engineering 14 Report No: RG2907

Hardscaped areas: 4 2% slope for 10'-0" required

(2 1/2" of fall over 10')

Compacted Structural Fill

Exterior flat work or pavement

Direct roof drainage away from foundation in accordance with

R401.3 & R801.3 (2018 IRC) or

1804.4 (2018 IBC)

Final grading

Landscaped areas: 4 5% slope for 10'-0" required

(6" of fall over 10')

Depth of overexcavation under slab or flat work =

1 ft

2 ft

Width of overexcavation 2

2 ft

Width of overexcavation 2

Footing 2 ft

Depth of 1 overexcavation

Total width of Native soil

2 ft2 ft

Footing 2 ft

Depth of 1 overexcavation

Total width of overexcavation 3

Width of overexcavation 2

Width of overexcavation 2

Depth of overexcavation under slab or flat work =

1 ft www.gemengineeringinc.com

April 25, 2022

Johansen & Tuttle PO Box 487 Castle Dale, Utah 84513

Email: jonathan@jandtengineering.com Phone: (435) 381-2523

Subject: Addendum # 1 - Seismic Refraction Survey Analysis

Gunlock State Park Geotechnical Report GEM Engineering Report # 2907. Dated March 16, 2022

INTRODUCTION

Upon completion of this seismic refraction survey taken at sites T-1 and T-2, we have compiled a summary and analysis of the accompanying data to better define the average depth to bedrock at sites T-1 and T-2.

A seismic refraction survey was conducted at sites T-1 and T-2 by using a 24-channel seismograph system. Geophones were placed at intervals of 10’ with the seismic generator located between channels 12 and 13. Seismic energy was conducted throughout the substrata by using a generic sledge, plate, and trigger system. Raw seismic refraction data was then captured and graphed in situ by the seismograph for later interpretation and analysis.

Vp CALCULATION

Once the raw data was captured and brought back to the lab, we were able to attain appropriate values for the bulk and shear moduli based on the soils report and the soil descriptions at sites T- 1 and T-2. With this information we were able to calculate the seismic velocity of the compressional waves (p-waves) as they travelled through the site-specific materials at sites T-1 and T-2 using the following equation for finding the velocity of a compressional wave:

= + 43

Bulk and shear moduli values were taken from “Evaluation of LS-DYNA Soil Material Model 147 by the US Department of Transportation, November 2004” and were determined to be as follows:

mailto:jonathan@jandtengineering.com

Page 11 August 8, 2017

T-1 Bulk Modulus (k) in Mpa 8.050 × 10 Shear Modulus (µ) in Mpa 4.830 × 10

T-2 Bulk Modulus (k) in Mpa 2.990 × 10 Shear Modulus (µ) in Mpa 1.794 × 10

Data from the soils report supplied the density value (ρ) to be 102.85 pcf for T-1 and 90.4 pcf for T-2. After calculations were ran, we obtained Vp values to be 296.57 m/s at T-1 and 192.79 m/s at T-2 respectively.

SEISMIC REFRACTION PROFILE

The values and data taken from the Vp portion of the report were then paired up with the data from the seismograph at sites T-1 and T-2. Analysis of both sets of data was done in such a manner as to extrapolate an average depth spanning the 24-channel seismic refraction string as well as a plus or minus (in ft.) value for better target acquisition during the drilling process.

CONCLUSION

At site T-1 we were able to find depth to bedrock at an average of 24.13’with a variation of 6 feet along the array. At site T-2 we located depth to bedrock at an average of 12.52’ with a variation of 6 feet along the array. The array of geo phones was feet long with the center being at the exploration locations.

Additionally, we recommend that the foundations for the bridge abutments be placed on drilled piers or piles which extend in to the bedrock a minimum of 10 feet. Additional recommendations can be given once the foundation type and scour analysis are determined and provided respectively.

We appreciate the opportunity to be of service on this project. All recommendation and limitation contained in the original subject geotechnical report apply. Please review the enclosed rule and review it with your well contractor once one is selected. Should you have any questions regarding this letter or wish to discuss additional services, please contact us at your convenience.

Respectfully submitted, GEM Engineering, Inc.

4/29/2022

Joel A. Myers, P.E.

Engineering Manager

Enclosure: Seismic refraction data.

Ginger Lindquist Highlight At site T-1 we were able to find depth to bedrock at an average of 24.13’with a variation of 6 feet along the array. At site T-2 we located depth to bedrock at an average of 12.52’ with a variation of 6 feet along the array.

Ginger Lindquist Highlight the foundations for the bridge abutments be placed on drilled piers or piles which extend in to the bedrock a minimum of 10 feet.

Ginger Lindquist Highlight in to the bedrock a minimum of 10 feet.

ENCLOSURE:

REFERENCES:

Reid, J. D. (2004). Chapter 4. Material Input Parameter Study. In Evaluation of LS-Dyna Soil

Material Model 147. essay, Turner-Fairbank Highway Research Center.

Phone (435) 867-6478 ♦ www.gemengineeringinc.com

April 25, 2022

Johansen & Tuttle PO Box 487 Castle Dale, Utah 84513

Email: jonathan@jandtengineering.com Phone: (435) 381-2523

Subject: Addendum # 2 - Driven Pile Design Values

Gunlock State Park Geotechnical Report GEM Engineering Report # 2907. Dated March 16, 2022

GEM Engineering has been requested to provide design values for driven piles at the site. The following information is provided as an addendum to the Geotechnical Investigation Report RG2907 – Dated 3/21/2022. It is our understanding that piles will be used for the bridge abutments with the west abutment located near the T-2 excavation and the East abutment located near the T-1 excavation.

Design parameters and assumptions are as follows

Estimated unconfined compressive strength of Navajo sandstone is 5800 psi Piles must be driven a minimum of 10 ft into bedrock. If piles cannot be driven into the bedrock a minimum of 10 ft, the piles will need to be pre-drilled and grouted a minimum of 10 feet into bedrock

The depth to bedrock was estimated by use of geophysical seismic analysis and could vary based on the actual location of the piles.

The values provided are for an individual pile.

It is assumed that all upper soils could be potentially scoured away in a flood event.

Due to potential scour of all upper soils design values for both the East and…