J.5 Attachment GFIGeotechReport-SaltLakePhase2.pdf

REPORT

GEOTECHNICAL STUDY

PROPOSED SALT LAKE RANGER DISTRICT

6914 SOUTH 3000 EAST

COTTONWOOD HEIGHTS, UTAH

Submitted To:

USDA – Forest Service IDAWY Acquisition Service Center

1405 Hollipark Drive Idaho Falls, Idaho 83401

Submitted By:

GSH Geotechnical, Inc.

473 West 4800 South

Salt Lake City, Utah 84123

June 11, 2021

Job No. 1019-033-21

J.5 Attachment-1240LT23R0024

GSH Geotechnical, Inc.

473 West 4800 South Salt Lake City, Utah 84123 Tel: 801.685.9190 Fax: 801.685.2990 www.gshgeo.com

June 11, 2021 Job No. 1019-033-21

Ms. Amelia Velasco USDA – Forest Service IDAWY Acquisition Service Center 1405 Hollipark Drive Idaho Falls, Idaho 83401

Ms. Velasco:

Re: Report

Geotechnical Study Proposed Salt Lake Ranger District 6914 South 3000 East Cottonwood Heights, Utah

1. INTRODUCTION

1.1 GENERAL

This report presents the results of our geotechnical study performed at the site of the proposed Salt Lake Ranger District to be located at 6914 South 3000 East, in Cottonwood Heights, Utah. The general location of the site with respect to existing roadways, as of 2021, is presented on Figure 1, Vicinity Map. A more detailed layout of the site showing proposed facilities, existing roadways, and the borings drilled in conjunction with this study is presented on Figure 2, Site Plan.

1.2 OBJECTIVES AND SCOPE

The objectives and scope of the study were planned in discussions between Ms. Amelia Velasco of USDA – Forest Service and Mr. Alan Spilker P.E. of GSH Geotechnical, Inc. (GSH).

In general, the objectives of this study were to:

1. Define and evaluate the subsurface soil and groundwater conditions across the site.

2. Provide appropriate foundation, earthwork, pavement, and geoseismic recommendations to be utilized in the design and construction of the proposed facilities.

USDA – Forest Service

Geotechnical Study - Proposed Salt Lake Ranger District

In accomplishing these objectives, our scope has included the following:

1. A field program consisting of the exploration, logging, and sampling of 2 borings.

2. A laboratory testing program.

3. An office program consisting of the correlation of available data, engineering analysis, and the preparation of this summary report.

1.3 AUTHORIZATION

Authorization was provided by returning a signed copy of the Work Order No. 1398 for Job Number 21002 dated 14 May 2021.

1.4 PROFESSIONAL STATEMENTS

Supporting data upon which our recommendations are based are presented in subsequent sections of this report. Recommendations presented herein are governed by the physical properties of the soils encountered in the exploration borings, projected groundwater conditions, and the layout and design data discussed in Section 2, Proposed Construction. If subsurface conditions other than those described in this report are encountered and/or if design and layout changes are implemented, GSH must be informed so that our recommendations can be reviewed and amended, if necessary.

Our professional services have been performed, our findings developed, and our recommendations prepared in accordance with generally accepted engineering principles and practices in this area at this time.

2. PROPOSED CONSTRUCTION

The project is to consist of the remodeling of the existing Salt Lake Ranger District office building, as well the construction of an addition to the existing structure including an engine bay and associated pavements. The structure is anticipated to be 1 to 2 stories above grade, with a below-grade elevator pit, and supported upon conventional spread and continuous wall footings.

Maximum real column and wall loads are anticipated to be on the order of up to 60 kips and up to 4 kips per lineal foot, respectively. Real loads are defined as the total of all dead plus frequently applied (reduced) live loads.

Paved parking areas and drive lanes are planned around the structures. Projected traffic in the parking areas is anticipated to consist of a light volume of automobiles and light trucks, occasional medium-weight trucks, and no heavyweight trucks. Proposed traffic in the drive lanes is anticipated to consist of a moderate volume of automobiles and light trucks, a light volume of medium-weight trucks, and occasional heavyweight trucks.

Site development will require some earthwork in the form of minor cutting and filling. At this time, we anticipate that maximum site grading cuts and fills, excluding utilities, will be on the order of 2 to 4 feet.

3. SITE INVESTIGATIONS

3.1 GENERAL

Subsurface conditions in unexplored locations or at other times may vary from those encountered at specific boring locations. If such variations are noted during construction or if project development plans are changed, GSH must review the changes and amend our recommendations, if necessary.

Boring locations were established by estimating distances and angles from site landmarks. If increased accuracy is desired by the client, we recommend that the boring locations and elevations be surveyed.

3.2 FIELD PROGRAM

To define and evaluate the subsurface soil and groundwater conditions across the site, 2 borings were completed within the accessible areas. These borings were completed to depths ranging from 2 to 4 feet with a rubber track-mounted drill rig equipped with hollow-stem augers. Auger refusal within very dense granular soils terminated each boring. The approximate locations of the borings are presented on Figure 2. The area investigated and the borehole locations were performed near the proposed building addition and new engine bay as identified on the site plan and outlined in the Statement of Work.

The field portion of our study was under the direct control and continual supervision of an experienced member of our geotechnical staff. During the course of the drilling operations, a continuous log of the subsurface conditions encountered was maintained. In addition, samples of the typical soils encountered were obtained for subsequent laboratory testing and examination. The soils were classified in the field based upon visual and textural examination. These classifications were supplemented by subsequent inspection and testing in our laboratory. Graphical representation of the subsurface conditions encountered is presented on Figures 3A and 3B, Boring Logs. Soils were classified in accordance with the nomenclature described on Figure 4, Key to Boring Log (USCS).

A 3.0-inch outside diameter, 2.42-inch inside diameter (Dames & Moore) was utilized at select locations and depths. The blow counts recorded on the boring logs were those required to drive the sampler 12 inches with a 140-pound hammer dropping 30 inches.

Following completion of exploration operations, the borings were backfilled with auger cuttings.

3.3 LABORATORY TESTING

3.3.1 General

To provide data necessary for our engineering analysis, a laboratory testing program was performed. This program included full gradation, moisture, partial gradation, and chemical tests.

The following paragraphs describe the tests and summarize the test data.

3.3.2 Full Gradation Test

Full- and partial-gradation tests were performed to aid in classifying soils. The tests results are tabulated on the following table and are presented on the borings logs, Figures 3A and 3B.

Boring No.

Depth (feet)

Percent Passing Sieve

3" 2" 1" 3/4" 3/8" No.

No.

No.

No.

No.

Soil Classification

B-2 0.5 100 100 95.3 84.4 45.0 31.7 23.8 9.4 0.6 6.6

SP/SC

(Fill/Roadbase)

3.3.3 Moisture and Partial Gradation Tests

To aid in classifying the granular soils, partial gradation tests were performed. Results of the tests are tabulated below and presented on the boring logs, Figures 3A and 3B.

Depth (feet)

Percent Passing No. 200 Sieve

Moisture Content Percent

Soil Classification

B-1 1.0 19.0 7.1 SM (Fill)

3.3.4 Chemical Tests

To determine if the site soils will react detrimentally with concrete, chemical tests were performed on a representative sample of the near-surface soil encountered at the site. The results of the chemical tests are tabulated below:

Depth (feet)

Soil Classification pH

Total Water-Soluble Sulfate (mg/kg-dry)

B-1 2.5 SM 8.28 578

4. SITE CONDITIONS

4.1 SURFACE

The site is located at 6914 South 3000 East in Cottonwood Heights, Utah. The site is currently developed with 2 office/garage buildings and associated pavements. The topography of the site is relatively flat, grading down to the northwest with a total relief of approximately 2 to 4 feet. Site vegetation consists of landscaped areas along the eastern border of the site.

The site is bounded to the north by single-family residential structures and associated pavements;

to the west by a residential subdivision and associated pavements; to the south by a retail/business structure; and to the east by the 3000 East Street followed by single-family residential structures.

4.2 SUBSURFACE SOIL

The following paragraphs provide generalized descriptions of the subsurface profiles and soil conditions encountered within the borings conducted during this study. As previously noted, soil conditions may vary in unexplored locations.

The borings were completed to depths ranging from 2 to 4 feet. The soil conditions encountered in each of the borings, to the depths completed, were generally similar across the boring locations.

Boring B-2 was performed within an existing parking lot area and encountered up to

2.0 inches of asphalt and up to 6.0 inches of aggregate base.

Non-engineered fill soils were encountered in both borings, to depths ranging from 1.5 to

3.0 feet beneath the existing ground surface. The non-engineered fill soils consisted of clay with silt, sand, and gravel content and sand with clay, silt, and gravel content.

Natural soils were encountered below the non-engineered fill in Boring B-1. The natural soils consisted primarily of sand with silt and gravel content.

Materials causing auger/excavation refusal were encountered within dense natural soils in Borings B-1 and B-2 at depths ranging from 2 feet to 4 feet below the existing ground surface.

The natural sand soils were medium dense, slightly moist, and dark brown in color. The natural sand soils are anticipated to exhibit moderately high strength and moderately low compressibility characteristics under the anticipated load range.

For a more descriptive interpretation of subsurface conditions, please refer to Figures 3A and 3B, Boring Logs. The lines designating the interface between soil types on the boring logs generally represent approximate boundaries. In situ, the transition between soil types may be gradual.

4.3 GROUNDWATER

Groundwater was not encountered in the borings performed for this exploration. However, we note that the borings encountered excavation refusal at relatively shallow depths of 2 to 4 feet beneath the existing ground surface. It is possible that groundwater may be encountered within excavations below these depths.

Groundwater levels vary with changes in season and rainfall, construction activity, irrigation, snow melt, surface water run-off, and other site-specific factors.

5. DISCUSSIONS AND RECOMMENDATIONS

5.1 SUMMARY OF FINDINGS

The proposed structures may be supported upon conventional spread and continuous wall foundations supported upon suitable natural granular soils and/or structural fill extending to suitable natural granular soils.

The most significant geotechnical aspects at the site are:

1. The existing non-engineered fills encountered at the site.

2. The shallow depth to auger refusal in both borings.

Prior to proceeding with construction, removal of the surface vegetation, root systems, topsoil, non-engineered fill, and any deleterious materials from beneath an area extending out at least 5 feet from the perimeter of the proposed structure footprints and 3 feet beyond rigid pavements and exterior flatwork areas will be required. All existing utility locations should be reviewed to assess their impact on the proposed construction and abandoned and/or relocated as appropriate.

Due to the developed nature of this site and the surrounding area, additional non-engineered fills may exist in unexplored areas of the site. Based on our experience, non-engineered fills are frequently erratic in composition and consistency. All surficial loose/disturbed soils and non-engineered fills must be removed below all footings, floor slabs, and rigid pavements. The in situ, non-engineered fills may remain below flexible pavements if free of any deleterious materials, of limited thickness, and if properly prepared, as discussed later in this report.

On-site granular soils, including some of the existing non-engineered fills, may be re-utilized as structural site grading fill if they meet the criteria for such, as stated later in this report.

The dense natural soils encountered at the refusal depths may require significant effort to excavate and should be considered in the design and bidding process.

Detailed discussions pertaining to earthwork, foundations, pavements, and the geoseismic setting of the site are presented in the following sections.

5.2 EARTHWORK

5.2.1 Site Preparation

Initial site preparation will consist of the removal of the non-engineered fills, surface vegetation, root systems, topsoil, and any deleterious materials from beneath an area extending out at least 5 feet from the perimeter of the proposed structure footprint and 3 feet beyond rigid pavements and exterior flatwork areas. All existing utility locations should be reviewed to assess their impact on the proposed construction and abandoned and/or relocated as appropriate.

In situ, non-engineered fills may remain below flexible pavements if free of debris and deleterious materials, less than 3 feet in thickness, and if properly prepared. Proper preparation below pavements will consist of the scarification of the upper 12 inches below the asphalt pavement sequence, followed by moisture preparation and re-compaction to the requirements of structural fill. Even with proper preparation, pavements established overlying non-engineered fills may encounter some long-term movements unless the non-engineered fills are completely removed.

It must be noted that from a handling and compaction standpoint, soils containing high amounts of fines (silts and clays) are inherently more difficult to rework and are very sensitive to changes in moisture content, requiring very close moisture control during placement and compaction. This will be very difficult, if not impossible, during wet and cold periods of the year. Additionally, the on-site soils are likely above optimum moisture content for compacting at present and would require some drying prior to re-compacting.

Subsequent to stripping and prior to the placement of floor slabs, foundations, structural site grading fills, exterior flatwork, and pavements, the exposed subgrade must be proof rolled by passing moderate-weight rubber tire-mounted construction equipment over the surface at least twice. If excessively soft or otherwise unsuitable soils are encountered beneath footings, they must be completely removed. If removal depth required is greater than 2 feet below footings, GSH must be notified to provide further recommendations. In pavement, floor slab, and outside flatwork areas, unsuitable natural soils should be removed to a maximum depth of 2 feet and replaced with compacted granular structural fill.

Subgrade preparation as described must be completed prior to placing overlying structural site grading fills.

GSH must be notified prior to the placement of structural site grading fills, floor slabs, footings, and pavements to verify that all loose/disturbed soils and non-engineered fills have been completely removed and/or properly prepared.

5.2.2 Temporary Excavations

Temporary excavations up to 8 feet deep in fine-grained cohesive soils, above or below the water table, may be constructed with sideslopes no steeper than one-half horizontal to one vertical (0.5H:1.0V). Excavations deeper than 8 feet are not anticipated at the site.

For granular (cohesionless) soils, construction excavations above the water table, not exceeding 4 feet, should be no steeper than one-half horizontal to one vertical (0.5H:1.0V). For excavations up to 8 feet, in granular soils and above the water table, the slopes should be no steeper than one horizontal to one vertical (1H:1V). Excavations encountering saturated cohesionless soils will be very difficult and will require very flat sideslopes and/or shoring, bracing, and dewatering.

Due to the relatively shallow refusal depths, difficult excavation should be anticipated within deeper excavations such as those for construction of utilities.

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

5.2.3 Structural Fill

Structural fill is defined as all fill which will ultimately be subjected to structural loadings, such as imposed by footings, floor slabs, pavements, etc. Structural fill will be required as backfill over foundations and utilities, as site grading fill, and as replacement fill below footings. All structural fill must be free of surface vegetation, root systems, rubbish, topsoil, frozen soil, and other deleterious materials.

Structural site grading fill is defined as structural fill placed over relatively large open areas to raise the overall grade. For structural site grading fill, the maximum particle size shall not exceed 4 inches; although, occasional larger particles, not exceeding 8 inches in diameter, may be incorporated if placed randomly in a manner such that “honeycombing” does not occur and the desired degree of compaction can be achieved. The maximum particle size within structural fill placed within confined areas shall be restricted to 2 inches.

On-site soils, including existing non-engineered fills, may be re-utilized as structural site grading fill if they do not contain construction debris or deleterious material and meet the requirements of structural fill. Fine-grained soils will require very close moisture control and may be very difficult, if not impossible, to properly place and compact during wet and cold periods of the year.

Imported structural fill below foundations and floor slabs shall consist of a well graded sand and gravel mixture with less than 30 percent retained on the three-quarter-inch sieve and less than 20 percent passing the No. 200 Sieve (clays and silts).

To stabilize soft subgrade conditions (if encountered) or where structural fill is required to be placed closer than 2.0 feet above the water table at the time of construction, a mixture of coarse angular gravels and cobbles and/or 1.5- to 2.0-inch gravel (stabilizing fill) should be utilized. It may also help to utilize a stabilization fabric, such as Mirafi 600X or equivalent, placed on the natural ground if 1.5- to 2.0-inch gravel is used as stabilizing fill.

5.2.4 Fill Placement and Compaction

All structural fill shall be placed in lifts not exceeding 8 inches in loose thickness. Structural fills shall be compacted in accordance with the percent of the maximum dry density as determined by the AASHTO1 T180 (ASTM2 D1557) compaction criteria in accordance with the following table:

Location Total Fill Thickness

(feet)

Minimum Percentage of Maximum Dry Density

Beneath an area extending at least 5 feet beyond the perimeter of the structure

0 to 10 95

Site grading fills outside area defined above

0 to 5 90

Site grading fills outside area defined above

5 to 10 95

Utility trenches within structural areas

-- 96

Road base -- 96

Structural fills greater than 10 feet thick are not anticipated at the site.

Subsequent to stripping and prior to the placement of structural site grading fill, the subgrade shall be prepared as discussed in Section 5.2.1, Site Preparation, of this report. In confined areas, subgrade preparation should consist of the removal of all loose or disturbed soils.

Coarse angular gravel and cobble mixtures (stabilizing fill), if utilized, shall be end dumped, spread to a maximum loose lift thickness of 15 inches, and compacted by dropping a backhoe bucket onto the surface continuously at least twice. As an alternative, the stabilizing fill may be compacted by passing moderately heavy construction equipment or large self-propelled compaction equipment over the surface at least twice. Subsequent fill material placed over the coarse gravels and cobbles shall be adequately compacted so that the “fines” are “worked into” the voids in the underlying coarser gravels and cobbles. Where soil fill materials are to be placed directly over more than about 18 inches of clean gravel, a separation geofabric, such as Mirafi 140N or equivalent, is recommended to be placed between the gravel and subsequent soil fills.

1 American Association of State Highway and Transportation Officials 2 American Society for Testing and Materials

Non-structural fill may be placed in lifts not exceeding 12 inches in loose thickness and compacted by passing construction, spreading, or hauling equipment over the surface at least twice.

5.2.5 Utility Trenches

All utility trench backfill material below structurally loaded facilities (footings, floor slabs, flatwork, pavements, etc.) shall be placed at the same density requirements established for structural fill. If the surface of the backfill becomes disturbed during the course of construction, the backfill shall be proof rolled and/or properly compacted prior to the construction of any exterior flatwork over a backfilled trench. Proof rolling shall be performed by passing moderately loaded rubber tire-mounted construction equipment uniformly over the surface at least twice. If excessively loose or soft areas are encountered during proof rolling, they shall be removed to a maximum depth of 2 feet below design finish grade and replaced with structural fill.

Many utility companies and City-County governments are now requiring that Type A-1a or A-1b (AASHTO Designation – granular soils with limited fines) soils be used as backfill over utilities.

These organizations are also requiring that in public roadways, the backfill over major utilities be compacted over the full depth of fill to at least 96 percent of the maximum dry density as determined by the AASHTO T180 (ASTM D1557) method of compaction. GSH recommends that as the major utilities continue onto the site that these compaction specifications are followed.

Fine-grained soils, such as silts and clays, are not recommended for utility trench backfill in structural areas.

Due to the relatively shallow refusal depths, difficult excavation should be anticipated within deeper excavations such as those for construction of utilities.

5.3 GROUNDWATER

Groundwater was not encountered in any of the borings performed for this exploration. However, we note that the borings encountered excavation refusal at relatively shallow depths of 2.0 to

4.0 feet beneath the existing ground surface. It is possible that groundwater may be encountered within excavations below these depths.

The groundwater measurements presented are conditions at the time of the field exploration and may not be representative of other times or locations. Groundwater levels may vary seasonally and with precipitation, as well as other factors including irrigation. Evaluation of these factors is beyond the scope of this study. Groundwater levels may, therefore, be at shallower or deeper depths than those measured during this study, including during construction and over the life of the structure.

The extent and nature of any dewatering required during construction will be dependent on the actual groundwater conditions prevalent at the time of construction and the effectiveness of construction drainage to prevent run-off into open excavations.

5.4 SPREAD AND CONTINUOUS WALL FOUNDATIONS

5.4.1 Design Data

The results of our analysis indicate that the proposed structures may be supported upon conventional spread and continuous wall foundations established upon suitable natural granular soils and/or structural fill extending to suitable natural granular soils. Under no circumstances shall foundations be established over non-engineered fills, loose or disturbed soils, topsoil, surface vegetation, root systems, rubbish, construction debris, other deleterious materials, frozen soils, or within ponded water. For design, the following parameters are provided:

Minimum Recommended Depth of Embedment for

Frost Protection - 30 inches

Minimum Recommended Depth of Embedment for Non-frost Conditions - 15 inches

Recommended Minimum Width for Continuous Wall Footings - 18 inches

Minimum Recommended Width for Isolated Spread Footings - 24 inches

Recommended Net Bearing Capacity for Real Load Conditions For Footings Established on Suitable Natural Granular Soils - 3,000 pounds per square foot

Bearing Capacity Increase for Seismic Loading - 50 percent

The term “net bearing capacity” refers to the allowable pressure imposed by the portion of the structure located above lowest adjacent final grade. Therefore, the weight of the footing and backfill to lowest adjacent final grade need not be considered. Real loads are defined as the total of all dead plus frequently applied live loads. Total load includes all dead and live loads, including seismic and wind.

5.4.2 Installation

Under no circumstances shall the footings be installed upon non-engineered fills, loose or disturbed soils, topsoil, surface vegetation, root systems, rubbish, construction debris, or other deleterious materials. If unsuitable soils are encountered, they must be removed and replaced with compacted granular fill. If granular soils become loose or disturbed, they must be recompacted prior to pouring the concrete.

The width of structural replacement fill below footings should be equal to the width of the footing plus one foot for each foot of fill thickness.

5.4.3 Settlements

Based on column loadings, soil bearing capacities, and the foundation recommendations as discussed above, we expect primary total settlement beneath individual foundations to be less than one inch.

The amount of differential settlement is difficult to predict because the subsurface and foundation loading conditions can vary considerably across the site. However, we anticipate differential settlement between adjacent foundations could vary from 0.5 to 0.75 inch. The final deflected shape of the structure will be dependent on actual foundation locations and loading.

5.5 LATERAL RESISTANCE

Lateral loads imposed upon foundations due to wind or seismic forces may be resisted by the development of passive earth pressures and friction between the base of the footings and the supporting soils. In determining frictional resistance, a coefficient of friction of 0.40 for footing interface with natural granular soils or granular structural fill. Passive resistance provided by properly placed and compacted granular structural fill above the water table may be considered equivalent to a fluid with a density of 300 pounds per cubic foot. Below the water table, this granular soil should be considered equivalent to a fluid with a density of 150 pounds per cubic foot.

A combination of passive earth resistance and friction may be utilized provided that the friction component of the total is divided by 1.5.

5.6 LATERAL PRESSURES

Parameters, as presented within this section, are for backfills which will consist of drained soil placed and compacted in accordance with the recommendations presented herein.

The lateral pressures imposed upon subgrade facilities will, therefore, be basically dependent upon the relative rigidity and movement of the backfilled structure. For active walls, such as retaining walls which can move outward (away from the backfill), drained backfill may be considered equivalent to a fluid with a density of 40 pounds per cubic foot in computing lateral pressures. For more rigid subgrade walls that are not more than 10 inches thick, granular backfill may be considered equivalent to a fluid with a density of 50 pounds per cubic foot. For very rigid non-yielding walls, granular backfill should be considered equivalent to a fluid with a density of at least 60 pounds per cubic foot. The above values assume that the surface of the soils slope behind the wall is horizontal and that the granular fill within 3 feet of the wall will be compacted with hand-operated compacting equipment.

For seismic loading of below-grade walls, the uniform lateral pressures below, in pounds per square foot (psf), should be added based on wall depth and wall case:

Uniform Lateral Pressures

Wall Height (Feet)

Active Pressure Case (psf)

Moderately Yielding Case (psf)

At Rest/Non-Yielding Case (psf)

4 41 73 106

6 61 110 158

5.7 FLOOR SLABS

Floor slabs may be established upon suitable natural subgrade soils or structural fill extending to suitable natural soils. Under no circumstances shall floor slabs be established directly over non-engineered fills, loose or disturbed soils, sod, rubbish, construction debris, other deleterious materials, frozen soils, or within ponded water.

To facilitate curing of the concrete and to provide a capillary moisture break, it is recommended that floor slabs be directly underlain by at least 4 inches of “free-draining” fill, such as “pea” gravel or three-quarters to one-inch minus clean gap-graded gravel.

Settlement of lightly loaded floor slabs designed according to previous recommendations (average uniform pressure of 200 pounds per square foot or less) is anticipated to be less than one-quarter of an inch.

5.8 PAVEMENTS

The non-engineered fills will exhibit poor pavement support characteristics when saturated. All pavement areas must be prepared as previously discussed (see Section 5.2.1, Site Preparation).

Under no circumstances shall pavements be established over unprepared non-engineered fills, loose or disturbed soils, topsoil, surface vegetation, root systems, rubbish, construction debris, other deleterious materials, frozen soils, or within ponded water. With the subgrade soils and the projected traffic as discussed in Section 2, Proposed Construction, the pavement sections on the following pages are recommended.

Parking Areas

(Light Volume of Automobiles and Light Trucks, Occasional Medium-Weight Trucks, and No Heavyweight Trucks)

[1-3 equivalent 18-kip axle loads per day]

Flexible Pavements:

(Asphalt Concrete)

3.0 inches Asphalt concrete

8.0 inches Aggregate base

Over Properly prepared fills, natural subgrade soils, and/or structural site grading fill extending to properly prepared fills and/or natural subgrade soils

Rigid Pavements:

(Non-reinforced Concrete)

5.0 inches Portland cement concrete

(non-reinforced)

5.0 inches Aggregate base

Over Properly prepared natural subgrade soils and/or structural site grading fill extending to properly prepared natural subgrade soils

Drive Lanes

(Moderate Volume of Automobiles and Light Trucks, Light Volume of Medium-Weight Trucks, and Occasional Heavyweight Trucks)

[6 equivalent 18-kip axle loads per day]

Flexible Pavements:

(Asphalt Concrete)

3.0 inches Asphalt concrete

9.0 inches Aggregate base

Over Properly prepared fills, natural subgrade soils, and/or structural site grading fill extending to properly prepared fills and/or natural subgrade soils

Rigid Pavements:

(Non-reinforced Concrete)

6.0 inches Portland cement concrete

(non-reinforced)

5.0 inches Aggregate base

Over Properly prepared natural subgrade soils and/or structural site grading fill extending to properly prepared natural subgrade soils

For dumpster pads, we recommend a pavement section consisting of 8.0 inches of Portland cement concrete, 12.0 inches of aggregate base, over properly prepared natural subgrade or site grading structural fills. Dumpster pads should not be constructed overlying non-engineered fills under any circumstances.

These above rigid pavement sections are for non-reinforced Portland cement concrete. Concrete should be designed in accordance with the American Concrete Institute (ACI) and joint details should conform to the Portland Cement Association (PCA) guidelines. The concrete should have a minimum 28-day unconfined compressive strength of 4,000 pounds per square inch and contain 6 percent 1 percent air-entrainment.

The crushed stone should conform to applicable sections of the current Utah Department of Transportation (UDOT) Standard Specifications. All asphalt material and paving operations should meet applicable specifications of the Asphalt Institute and UDOT. A GSH technician shall observe placement and perform density testing of the base course material and asphalt.

Please note that the recommended pavement section is based on estimated post-construction traffic loading. If the pavement is to be constructed and utilized by construction traffic, the above pavement section may prove insufficient for heavy truck traffic, such as concrete trucks or tractor-trailers used for construction delivery. Unexpected distress, reduced pavement life, and/or premature failure of the pavement section could result if subjected to heavy construction traffic and the owner should be made aware of this risk. If the estimated traffic loading stated herein is not correct, GSH must review actual pavement loading conditions to determine if revisions to these recommendations are warranted.

5.9 CEMENT TYPES

The laboratory tests indicate that the natural clay soils tested contain a moderate amount of water-soluble sulfates. Based on our test results, concrete in contact with the on-site soil will have a moderate potential for sulfate reaction (ACI 318, Table 4.3.1). To achieve the required protection against sulfate-related corrosion, we recommend a maximum water-to-cement ratio of 0.5 (by weight, normal weight aggregate concrete) and using Type II cement in concrete to obtain a minimum compressive strength of 4,000 pounds per square inch (psi). Details can be found in the above ACI reference and in the Portland Cement Association publication, “Design and Control of Concrete Admixtures.”

5.10 GEOSEISMIC SETTING

5.10.1 General

Utah municipalities have adopted the International Building Code (IBC) 2018. The IBC 2018 code refers to ASCE 7-16 Minimum Design Loads and Associated Criteria for Buildings and Other Structures (ASCE 7-16) determines the seismic hazard for a site based upon mapping of bedrock accelerations prepared by the United States Geologic Survey (USGS) and the soil site class. The USGS values are presented on maps incorporated into the IBC code and are also available based on latitude and longitude coordinates (grid points).

5.10.2 Faulting

Based on our review of available literature, no active faults pass through or immediately adjacent to the site. The nearest active mapped fault consists of the Salt Lake City Section of the Wasatch Fault, located about 0.57 mile to the northeast of the site.

5.10.3 Site Class

For dynamic structural analysis, the Site Class D – Default Soil Profile as defined in Chapter 20 of ASCE 7-16 (per Section 1613.3.2, Site Class Definitions, of IBC 2018) can be utilized. If a measured site class is desired based on the project structural engineer's evaluation and recommendations, additional testing and analysis can be completed by GSH to determine the measured site class. Please contact GSH for additional information.

5.10.4 Ground Motions

The IBC 2018 code is based on USGS mapping, which provides values of short and long period accelerations for average bedrock values for the Western United States and must be corrected for local soil conditions. The following table summarizes the peak ground and short and long period accelerations for the MCE event and incorporates the appropriate soil amplification factor for a Site Class D – Default* Soil Profile. Based on the site latitude and longitude (40.6254 degrees north and 111.8079 degrees west, respectively) and Risk Category I, the values for this site are tabulated below:

* If a measured site class in accordance with IBC 2018/ ASCE 7-16 is beneficial based on the project structural engineers review, please contact GSH for additional options for obtaining this measured site class.

**IBC 2018/ASCE 7-16 may require a site-specific study based on the project structural engineer’s evaluation and recommendations. If needed, GSH can provide additional information and analysis including a complete site-specific study in accordance with chapter 21 of ASCE 7-16.

5.10.5 Liquefaction

The site is located in an area that has been identified by the Utah Geological Survey (UGS) as being a “very low” liquefaction potential zone. Liquefaction is defined as the condition when saturated, loose, granular soils lose their support capabilities because of excessive pore water pressure, which develops during a seismic event. Clayey soils, even if saturated, will generally not liquefy during a major seismic event.

Due to the density of the granular soils, liquefaction is not anticipated to occur within the soils encountered at this site.

Spectral Acceleration

Value, T

0.2 Seconds

(Short Period Acceleration)

SS = 137.6 Fa = 1.200 SMS = 165.1 SDS = 110.1

1.0 Second

(Long Period Acceleration)

S1 = 50.7 Fv = 1.793 SM1 = 90.9 SD1 = 60.6

Site Class D - Default*

(% g) class effects]

[adjusted for site Design Values**

(% g)(% g) [mapped values]

Boundary Bedrock

Site Coefficient

5.11 SITE VISITS

GSH must verify that all topsoil/disturbed soils and any other unsuitable soils have been removed, that non-engineered fills have been removed and/or properly prepared, and that suitable soils have been encountered prior to placing site grading fills, footings, slabs, and pavements. Additionally, GSH must observe fill placement and verify in-place moisture content and density of fill materials placed at the site.

5.12 CLOSURE

If you have any questions or would like to discuss these items further, please feel free to contact us at (801) 685-9190.

Respectfully submitted, GSH Geotechnical, Inc.

Alan D. Spilker, P.E.

State of Utah No. 334228 President/Senior Geotechnical Engineer

KSB/ADS:jlh

Encl. Figure 1, Vicinity Map

Figure 2, Site Plan Figures 3A and 3B, Log of Borings Figure 4, Key to Boring Log (USCS)

Addressee (email)

REFERENCE:

ALL TRAILS - NATIONAL GEOGRAPHIC TERRAIN

DATED 2021

FIGURE 1

VICINITY MAP

CASE, LOWE & HART

JOB NO. 1019-033-21

SITE

CASE, LOWE & HART

JOB NO. 1019-033-21

REFERENCE:

ADAPTED FROM AERIAL PHOTOGRAPH

DOWNLOADED FROM GOOGLE EARTH

IMAGERY DATED 11 SEPT 2020

FIGURE 2

SITE PLAN

200 ft

B-1

B-2

BORING: B-1

PROJECT NUMBER: 1019-033-21

DATE STARTED: 5/19/21 DATE FINISHED: 5/19/21

LOCATION: 6914 South 3000 East, Cottonwood Heights, Utah GSH FIELD REP.: AL

DRILLING METHOD/EQUIPMENT: 3-3/4" ID Hollow-Stem Auger HAMMER: Automatic WEIGHT: 140 lbs DROP: 30"

GROUNDWATER DEPTH: Not Encountered (5/19/21) ELEVATION: ---

SM dry FILL very stiff

CL moist FILL medium stiff

SM slightly moist medium dense

See Subsurface Conditions section in the report for additional information. FIGURE 3A with some fine to coarse sand and some fine and coarse gravel;

dark brown

SILTY FINE TO COARSE SAND, FILL

SILTY CLAY, FILL

PROJECT: Proposed Salt Lake Ranger District

CLIENT: Case, Lowe & Hart

BORING LOG

Page: 1 of 1 with some fine gravel and trace clay; major roots (topsoil) to 6";

REMARKSDESCRIPTION

dark brown

Ground Surface

SILTY FINE SAND

with fine and coarse gravel; dark brown Auger refusal at 4.0' on gravel.

No groundwater encountered at time of drilling.

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7.1

19.0

BORING: B-2

PROJECT NUMBER: 1019-033-21

DATE STARTED: 5/19/21 DATE FINISHED: 5/19/21

LOCATION: 6914 South 3000 East, Cottonwood Heights, Utah GSH FIELD REP.: AL

DRILLING METHOD/EQUIPMENT: 3-3/4" ID Hollow-Stem Auger HAMMER: Automatic WEIGHT: 140 lbs DROP: 30"

GROUNDWATER DEPTH: Not Encountered (5/19/21) ELEVATION: ---

SP/ slightly moist

SC

FILL

See Subsurface Conditions section in the report for additional information. FIGURE 3B with some clay; dark brown

Auger refusal at 2.0' on gravel.

No groundwater encountered at time of drilling.

DESCRIPTION REMARKS

Ground Surface

2" ASPHALT, 6" ROAD BASE

FINE AND COARSE GRAVELLY FINE TO COARSE SAND, FILL

CLIENT: Case, Lowe & Hart

PROJECT: Proposed Salt Lake Ranger District

BORING LOG

Page: 1 of 1

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4.0

6.6

CLIENT: Case, Lowe & Hart

PROJECT: Proposed Salt Lake Ranger District

PROJECT NUMBER: 1019-033-21

① ② ③ ④

CEMENTATION: MODIFIERS:

Trace

<5%

Some

5-12%

With

> 12%

USCS STRATIFICATION:

SYMBOLS

Occasional:

One or less per 6" of thickness

Numerous;

More than one per 6" of thickness

Note: Dual Symbols are used to indicate borderline soil classifications.

⑤ ⑥ ⑦ ⑧ ⑨ ⑩ ⑪

COLUMN DESCRIPTIONS

① Water Level: Depth to measured groundwater table. See symbol below.

⑩ Liquid Limit (%): Water content at which a soil changes from plastic to liquid behavior.

② USCS: (Unified Soil Classification System) Description of soils encountered; typical symbols are explained below.

DESCRIPTION REMARKS

⑪ Plasticity Index (%): Range of water content at which a soil exhibits plastic properties.

③ Description: Description of material encountered; may include color, moisture, grain size, density/consistency, ⑫ Remarks: Comments and observations regarding drilling or sampling made by driller or field personnel. May include other field and laboratory test results using the following abbreviations:

④ Depth (ft.): Depth in feet below the ground surface.

⑤ Blow Count: Number of blows to advance sampler 12" beyond first 6", using a 140-lb hammer with 30" drop.

MOISTURE CONTENT (FIELD TEST):

Weakly: Crumbles or breaks with handling or slight finger pressure.

Dry: Absence of moisture, dusty, dry to the touch.

⑥ Sample Symbol: Type of soil sample collected at depth interval shown; sampler symbols are explained below. Moderately: Crumbles or breaks with considerable finger pressure.

Moist: Damp but no visible water.

⑦ Moisture (%): Water content of soil sample measured in laboratory; expressed as percentage of dryweight of Strongly: Will not crumble or break with finger pressure.

Saturated: Visible water, usually soil below water table.

⑧ Dry Density (pcf): The density of a soil measured in laboratory; expressed in pounds per cubic foot.

Descriptions and stratum lines are interpretive; field descriptions may have been modified to reflect lab test results. Descriptions on the logs apply only at the specific boring locations and at the time the borings were advanced; they are not warranted to be representative of subsurface conditions at other locations or times.

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MAJOR DIVISIONS TYPICAL DESCRIPTIONS DESCRIPTION THICKNESS

COARSE-

GRAINED

SOILS

More than 50% of material is larger than No. 200 sieve size.

GRAVELS

More than 50% of coarse fraction retained on No. 4 sieve.

CLEAN

GRAVELS GW Well-Graded Gravels, Gravel-Sand Mixtures, Little or No Fines

(little or no fines)

Seam up to 1/8"

Layer 1/8" to 12"

(little or no fines) GP

Poorly-Graded Gravels, Gravel-Sand Mixtures, Little or No Fines

GRAVELS WITH

FINES GM Silty Gravels, Gravel-Sand-Silt Mixtures

Standard Penetration Split Spoon Sampler

(appreciable amount of fines) GC Clayey Gravels, Gravel-Sand-Clay Mixtures TYPICAL SAMPLER

SANDS

More than 50% of coarse fraction passing through No. 4 sieve.

CLEAN SANDS SW Well-Graded Sands, Gravelly Sands, Little or No Fines

GRAPHIC SYMBOLS

SILTS AND CLAYS Liquid Limit greater than

50%

MH Inorganic Silts, Micacious or Diatomacious Fine Sand or Silty Soils

California Sampler

SP Poorly-Graded Sands, Gravelly Sands, Little or No Fines Bulk/Bag Sample

SANDS WITH

FINES SM Silty Sands, Sand-Silt Mixtures

Peat, Humus, Swamp Soils with High Organic Contents

WATER SYMBOL

Water Level

Inorganic Clays of Low to Medium Plasticity, Gravelly Clays, Sandy Clays, Silty Clays, Lean Clays

FINE-

GRAINED

SOILS

More than 50% of material is smaller than No. 200 sieve size.

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 Slight Plasticity

No Recovery

CL

FIGURE 4

KEY TO BORING LOG

⑫

% Passing 200: Fines content of soils sample passing a No. 200 sieve; expressed as a percentage.

CH

(appreciable amount of fines) SC Clayey Sands, Sand-Clay Mixtures Rock Core

PT

⑨

Inorganic Clays of High Plasticity, Fat Clays Thin Wall

OH Organic Silts and Organic Clays of Medium to High Plasticity

HIGHLY ORGANIC SOILS

3.25" OD, 2.42" ID

D&M Sampler

OL Organic Silts and Organic Silty Clays o f Low Plasticity

3.0" OD, 2.42" ID

D&M Sampler

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