3-22-211 Eagle Mountain Observatory Geotechnical Investigation 20220908.pdf

GEOTECHNICAL ENGINEERING

INVESTIGATION

Walden Park Observatory Geotechnical Investigation

Prepared For:

Eagle Mountain City Attn: Brad Hickman

1650 E Stagecoach Run Eagle Mountain, UT 84005

(801) 789-6664 Bhickman@emcity.org

Prepared By:

Civil Solutions Group, Inc.

John Powell, P.E.

Aaron Mackliet, Geotechnical Technician

498 West 100 S Providence, Utah 84332

Original Submittal: September 7, 2022 Job Number: 22-211

Walden Park Observatory Geotechnical Investigation ii September 7, 2022

RE: Walden Park Observatory Geotechnical Investigation

Dear Mr. Hickman, Per your request this geotechnical engineering investigation is submitted for the subject property located approximately at American Way and Frontier Street in Eagle Mountain, UT. This report contains the findings of the field investigation and the analysis conducted by Civil Solutions Group.

This report also contains recommendations pertaining to construction and design of earth related portions of this project.

Civil Solutions Group completed the field investigation on August 17, 2022 at which time three bore holes were drilled, examined, and recorded in detail. The bore locations were selected based upon the proposed location of the building footprint and other site features. Civil Solutions Group recommends the site is suitable for proposed construction within the parameters defined within this report. Thank you for the opportunity to provide these services to you.

Sincerely, John Powell, P.E.

Civil Solutions Group, Inc.

Walden Park Observatory Geotechnical Investigation iii September 7, 2022

Table of Contents

Executive Summary

Introduction

General

Objectives and Scope

Authorization

Professional Statements

Proposed Construction

Existing Site Conditions

General

Site Topography & Drainage Features

Site Soils

Subsurface Exploration and Testing Programs

General

Field Program

Laboratory Program

Moisture and Density

Sieve Analysis

Atterberg Limits

Consolidation

Chemical

Discussions & Recommendations

Summary of Findings

Earthwork

Site Preparation

Temporary Excavations

Structural Fill

Fill Placement and Compaction

Utility Trenches

Drainage

Structural Considerations

Spread and Continuous Wall Foundations

Lateral Resistance

Floor slabs

Walden Park Observatory Geotechnical Investigation iv September 7, 2022

Soil Corrosiveness

Cement Use

Construction Considerations

Geoseismic Setting

Faulting

Soil Class

Liquefaction

Groundwater

Closure

Glossary/Explanation of Terms or Procedures

Appendix

Table of Figures Figure 1 - Vicinity Map

Figure 2 - Site Map

Figure 3 - Looking West

Figure 4 – Looking South

Figure 5 – Key to Soil Logs

Table of Tables Table 1 - Gradation & Soil Classifications

Table 2 - Atterberg Limits

Table 3 - Chemical Properties of Soil

Table 4 – Structural Fill Gradation Requirements

Table 5 - Fill Compaction Requirements

Table 6 - Structural Design Parameters

Table 7 - Groundwater Depth

Walden Park Observatory Geotechnical Investigation 1 September 7, 2022

Executive Summary A geotechnical study was performed for the subject property at American Way and Frontier Street in Eagle Mountain, UT. Our scope of services included drilling three bore holes designated B-1 to B-3. The boreholes were drilled with hollow stem augers and advanced to a maximum depth of 25.5-feet below existing site grade. All field work was contained in the proposed development area and was completed on August 17, 2022.

The findings and recommendations generated from this exploration are summarized below:

• Onsite Soil – The site is composed of low plasticity silty clay. Groundwater was not encountered at the time of the site investigation.

• Foundations - The planned structure should be supported entirely on continuous spread footings or spot footings. The recommended bearing capacity of in-situ soil is 2,000 pounds per square foot.

• Seismic Considerations - The 2018 International Building Code Seismic Design Category for this site is Category D (Risk Category II), with a soil site class of D. The site is located in an area with very low liquefaction potential according to the Utah Geological Survey, and the in-situ soils encountered on site.

This summary should be used in conjunction with the entire report for design purposes. It should be recognized that details were not included or fully developed in this section, and the report must be read in its entirety for a comprehensive understanding of the items contained herein. The entire report should be read for an understanding of the report limitations.

Walden Park Observatory Geotechnical Investigation 2 September 7, 2022

Introduction

General

Civil Solutions Group, Inc. (CSG) was contacted by Mr. Hickman and was asked to conduct a geotechnical engineering investigation on the subject property located at American Way and Frontier Street in Eagle Mountain, UT. The general location of the site may be seen in Figure 1, Vicinity Map. A more detailed location of the site showing the proposed development and surrounding improvements is shown in Figure 2, Site Map. It was described that the proposed construction for the observatory is anticipated to be one story in height and of steel frame and wood frame construction.

Objectives and Scope

The objectives and scope of our study were defined between Mr. Hickman and Mr. Dayton Law of Civil Solutions Group. In general, the objectives of this study were to:

• Define and evaluate subsurface soil and groundwater conditions across the site

• Provide foundation, earthwork, drainage, and geo-seismic recommendations

To accomplish these objectives, our scope has included the following:

• A field program consisting of the drilling, logging, and sampling of the three borings

• A laboratory testing program

• An office program consisting of correlating available data, engineering analyses, and report preparation

Authorization

Civil Solutions Group, Inc. (CSG) was authorized to proceed with this scope of work through an executed contract returned to our office by Mr. Hickman of Eagle Mountain City. The executed contract was dated July 21, 2022.

Professional Statements

We at CSG certify that 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. Supporting data upon which our recommendations are based is presented in the subsequent sections of this report. Recommendation made herein are governed by the physical properties of the soils encountered in the exploration borings, observed and projected groundwater conditions, and the layout and design data as summarized in the Proposed Construction section of this report. If subsurface conditions other than those described in this report are encountered and/or if design and layout changes are implemented, CSG must be informed so that our recommendations can be reviewed and amended, if necessary.

Proposed Construction The proposed construction is as follows: observatory structure with utilities and walkways. It is anticipated to be one story in height of typical steel frame and wood frame construction. If structural engineering plans are different than assumed, they should be provided to our office for review.

Walden Park Observatory Geotechnical Investigation 3 September 7, 2022

The site development will likely require minimal earthwork. It is estimated that up to 3-foot cuts and/or fills will be required to achieve site grades and tie in-to the adjacent properties.

Column and wall loadings are anticipated to be on the order of 20-98 kips and 2-5 kips per lineal foot respectively.

Existing Site Conditions

General

The site lies approximately at American Way and Frontier Street in Eagle Mountain, UT. The existing property is grass, with a park sitting just north on the same property. The surrounding properties are residential homes. The surface and subsurface soils that were explored appeared to be free of hazardous debris and other foreign objects.

Site Topography & Drainage Features

The majority of the site is relatively flat, and sits on grade with surrounding properties. On-site there were no springs, streams, canals or standing water observed at the time of the site visit.

Site Soils

The soil conditions encountered in each of the three borings, to the depths explored, were relatively similar. In bore hole number 1 (B-1), there was approximately 0.5-feet of topsoil with roots extending from vegetation. From approximately 0.5-feet beneath existing grade to 5.5-feet we encountered light brown clayey silt with some sand. From 5.5-feet to the full depth explored, 25.5-feet, silty clay was encountered. The remaining bore holes throughout the site had similar characteristics as B-1. Groundwater was not encountered at the time of the site investigation. Soil encountered during the investigation can be referenced in the Soil Logs in the Appendix of this report. Materials encountered in the bore holes will exhibit required strength and compressibility characteristics under the anticipated loading range.

Subsurface Exploration and Testing Programs

General

To define and evaluate the subsurface soil and groundwater conditions across the site, three borings were drilled to depths of up to 25.5-feet below existing grade. The borings were drilled using a truck mounted drilling rig equipped with 3.25-inch inside diameter hollow stem augers. Soil sampling equipment was advanced through the hollow stem to retrieve both disturbed and relatively undisturbed samples of the in-situ soil. Locations of the borings are presented in Figure 2.

Field Program

The field portion of our study was conducted on August 17, 2022. Continuous logs of the subsurface findings were created and maintained as part of the field program. The field portion of our study was under the direct control and continual supervision of an experienced member of our geotechnical staff. Field classifications were logged, and any adjustments made once the laboratory data and analyses were received.

Walden Park Observatory Geotechnical Investigation 4 September 7, 2022

The CSG geotechnical team collected both disturbed and relatively undisturbed samples of typical soils that were found in the bore holes. The disturbed samples were taken using bagged grab samples and a SPT split spoon sampler. The SPT split spoon sampler had an outside diameter of 2-inches and an inside diameter of 1.38-inches. The sampler was driven into the undisturbed soil a total of 18-inches utilizing a 140-pound auto hammer falling a vertical distance of 30-inches. The blow counts recorded on the Soil Logs represent the total number of blows from the safety hammer that were required to drive the sampler the final 12-inches.

The CSG geotechnical team collected relatively undisturbed samples of the fine-grained materials using thin-walled Shelby Tube sampler with an outside diameter of 3-inches. The sampler was pressed into the in-situ soil using the drill. To compensate for any disturbance caused during sample collection, the sample was trimmed in the lab.

Graphical depictions of the subsurface findings are shown in the Soil Logs contained within the Appendix of this report.

Laboratory Program

CSG partnered with RB&G Engineering to conduct a laboratory testing program on the samples retrieved from the sites. This laboratory testing program was conducted to provide data necessary for our engineering analyses. The program included moisture and density, partial gradation (sieve) analysis, Atterberg limits (if applicable), consolidation, and chemical tests. The following describes the tests and summarize the test data. Samples from the field will be maintained in our office for a period of 90 days at which time they will be disposed of unless a written request is received from Eagle Mountain City that they should be retained.

Moisture and Density

Moisture and density tests were performed on selected relatively undisturbed samples collected from the bore holes. Understanding the relationship between moisture and density in the in-situ soil aids in classifying the soils. The results of these tests are presented on the Soil Logs found in the Appendix.

Sieve Analysis

Gradation tests (sieve analysis) were conducted on disturbed samples which were collected from the site. The gradation test aids in classifying the soils and can provide general index parameters.

Gradation tests aid the design team in determining the overall composition of the soil and behaviors that the soil may exhibit under certain situations. The results of the tests are shown in Table 1 below:

Table 1 - Gradation & Soil Classifications

Boring Sample No.

Depth (feet) Percent Passing #200 Sieve

Soil Classification

B-1.2 4-5.5 85 ML

B-1.4 9-11 99 CL

B-1.7 24-25.5 97 CL

B-2.5 14-15.5 85 CL

Walden Park Observatory Geotechnical Investigation 5 September 7, 2022

Atterberg Limits

Atterberg Limits were performed on relatively undisturbed samples to understand the plastic and liquid limits of the cohesive soil. Atterberg limits allow the design team to understand the potential for the soil to shrink and expand based on water content. The results are presented in Table 2 below:

Table 2 - Atterberg Limits

Boring Sample No.

Depth (feet)

Classification Liquid Limit (LL)

Plastic Limit (PL)

Plasticity Index (PI)

B-1.2 4-5.5 ML -- -- NP

B-1.4 9-11 CL 35 16 19

B-1.7 24-25.5 CL 38 23 15

B-2.5 14-15.5 CL 21 13 8

Consolidation

A consolidation test was performed on a relatively undisturbed sample of the fine-grained soils as sampled in the bore holes. A consolidation test allows the design team to understand the potential for the in-situ soil to settle over time and under loading conditions. The results of the consolidation tests are maintained in our office and may be requested as necessary.

Chemical

To determine if the site soils will react detrimentally with concrete, a chemical sulfate test was performed on a representative sample of the natural soils at approximately the depth of the soil that will come into direct contact with concrete improvements for the proposed development. The results of the chemical tests are shown in Table 3 below:

Table 3 - Chemical Properties of Soil

Boring Sample No. Depth (feet) Sulfate (mg/kg) B-3.1 4-5.5 29

Discussions & Recommendations

Summary of Findings

It is recommended that the owner have a CSG field engineer or a qualified assistant oversee the site work, especially the footing excavation and preparation. Also, the building code requires inspection and reports on all structural site work.

Detailed discussions pertaining to earthwork, structural considerations, geoseismic setting, and groundwater are included in the following sections:

Walden Park Observatory Geotechnical Investigation 6 September 7, 2022

Earthwork

Site Preparation

Initial site preparation will consist of the removal of surface vegetation, topsoil, root balls, sod or any other deleterious materials extending at least three feet beyond the perimeter of all areas to be developed. Non-engineered fills will be completely removed three feet beyond the extents of all spread and continuous footings, rigid pavement areas, floor slabs and other areas that require a stabilized foundation. Stripped materials consisting of vegetation and organic materials should be wasted from the site or used to revegetate landscape areas.

Non-engineered fills may remain in areas where flexible pavements are to be placed if they are properly prepared. Proper preparation will consist of scarifying and moisture conditioning the upper nine inches and recompacting to the requirements of structural fill. It should be noted that compaction of fine-grained soils (silts and clays) as site grading fill will be very difficult, if not impossible, during wet and cold periods of the year.

The exposed natural subgrade should be proof-rolled prior to the placement of structural site grading fill, footings, floor slabs, or any other structural improvement made to the site. The proof-roll should be completed by driving a loaded piece of construction equipment, mounted with rubber tires, over the exposed natural subgrade surface at least twice. A CSG field engineer should oversee the proof roll and provide recommendations as needed. Soft spots should be completely excavated and removed if they are discovered. The soft spots should be replaced with granular structural fill. It is not anticipated that removal depth would be more than 2 vertical feet. If an excavation of more than 2 vertical feet is required, CSG should be notified to provide further recommendation.

In flexible pavement areas, unsuitable materials encountered during compaction and proof-rolling operations must be removed to a maximum depth of two feet and replaced with compacted granular structural fill.

Although evidence of underground facilities such as utilities, septic tanks, cesspools, basements, etc.

was not observed during the field investigation, such features could be encountered during construction. If unexpected fills, debris or underground facilities are encountered, such features should be removed, and the excavation thoroughly cleaned prior to backfill placement and/or construction.

Temporary Excavations

All temporary excavations should follow OSHA Sloping and Benching – 1926 Subpart P App B requirements, which take precedence over any recommendations presented in this report.

Temporary excavations in cohesive soil, above or below the water table, not exceeding four feet in depth, may be excavated with nearly vertical sideslopes. Excavations within loose and/or cohesionless soils will be very difficult as they tend to flow into the excavation. They will require very flat sideslopes and/or shoring, bracing and dewatering.

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

Walden Park Observatory Geotechnical Investigation 7 September 7, 2022

Structural Fill

The on-site native soils were finer by nature and cannot be used as structural fill. However, the on-site soils can be used as fill in landscape areas that are not expected to carry a load. The use of fine-grained soils (silts and clays) as landscape fill will be very difficult, if not impossible, during wet and cold periods of the year. Proper moisture control and conditioning will be required.

Fine-grained soils (silts and clays) are not recommended as structural fill in confined areas, such as around foundations and within utility trenches. This fill material should be composed of granular material.

All imported granular structural fill should consist of a fairly well-graded mixture of sand and gravel containing less than 15 percent fines (percent by weight of material passing the No. 200 sieve).

To stabilize soft subgrade conditions (if required), a mixture of coarse gravels and cobbles (stabilizing fill) should be utilized. A layer of 12 to 18 inches thick of stabilizing fill is typically sufficient to stabilize most soft/disturbed areas.

Table 4 shown below is indicative of the material that should be used as structural fill and road base throughout the site:

Table 4 – Structural Fill Gradation Requirements

Fill Type * Application Requirements

Gradation Plasticity

Size % Finer by Weight

Structural Fill Required for all fill under foundations and floor slabs

3-inch No. 4 Sieve

No. 200 Sieve

25 - 60 15-max

Liquid Limit 30-max Plasticity Index 6-max

Site Grading Fill

Fill in pavement and non-structural areas

4-inch No. 200 Sieve

35-max

Liquid Limit 36-max Plasticity Index 10-max

Stabilization Fill

Fill used to stabilize soft, potentially pumping subgrade

5-inch No. 200 Sieve

5-max

NA

Free Draining Granular Backfill

Retaining Walls 1½-inch 1-inch ½-inch No. 4

95 – 100 25 – 60 5-max

NA

Road Base Fill used under the pavement sections

3/4” 3/8”

No. 10 No. 40 No. 200

78-92 55-67 28-38 7-11

Non-Plastic

*All fill should consist of approved materials that are free of organic matter and debris. Frozen material should not be used, and fill should not be placed on a frozen subgrade. A sample of each material type should be submitted to the geotechnical engineer for evaluation.

Walden Park Observatory Geotechnical Investigation 8 September 7, 2022

Fill Placement and Compaction

All fill should be placed in lifts not exceeding 8 inches in loose thickness. Moisture should be adjusted to within ± 2% of optimum moisture content. Lifts will need to be compacted in thinner lifts if smaller compaction equipment is used. Structural fills should be compacted in accordance with the percent of maximum dry density as determined by the AASHTO T-180 (ASTM D-1557) compaction criteria and according to Table 5 below:

Table 5 - Fill Compaction Requirements

Location Total Fill Thickness (feet)

Minimum Percentage of Maximum Dry Density

Beneath an area extending at least 3 feet beyond the footprint of a structure

0 to 8 95

Beneath pavements and travelled ways

0 to 8 95

Landscaped areas or areas not expected to carry a load

0 to 5 85

Landscaped areas or areas not expected to carry a load

5 to 8 92

Road Base - 96

Prior to placement of fills, the subgrade must be prepared as discussed in the Site Preparation section of this report. In confined areas, subgrade preparation should consist of the removal of all loose and disturbed soils. Fill should be tested frequently for moisture content and compaction during placement. Should the results of the in-situ density tests indicate the specified moisture or compaction limits have not been met, the area represented by the test should be reworked and retested as required until the specified compaction is achieved. This may require adjustment of the moisture content.

Utility Trenches

We recommend that all utility trenches on-site or as a part of this site, should utilize a Type A-1a or A-1b (AASHTO Designation) soil as backfill material. The on-site materials can be used for trench backfill if they meet these classifications and are properly moisture conditioned. This should be verified by the materials testing agency. All utility trenches which will ultimately bear structural loads should be compacted at the structural density requirements established in Table 5.

Drainage

Positive drainage should be provided during construction and maintained throughout the life of the development. Infiltration of water into utility trenches or foundation excavations should be prevented. Planters and other surface features which might retain water in areas adjacent to the buildings or pavements should be sealed, mechanically drained, or eliminated. In areas where sidewalks or paving do not immediately adjoin the structure, we recommend that protective slopes be provided with a minimum grade of approximately five percent for at least 10 feet from perimeter walls. Backfill against footings, exterior walls, and in utility and sprinkler line trenches should be well compacted and free of all construction debris to reduce the possibility of moisture infiltration. Roof runoff should be collected in rain gutters and downspouts. Downspouts, roof drains or scuppers

Walden Park Observatory Geotechnical Investigation 9 September 7, 2022 should discharge into extensions when the ground surface beneath such features is not protected by exterior slabs or paving to divert collected water a minimum of 10 feet away from structures.

Sprinkler systems should not be installed within five feet of foundation walls. Landscaped irrigation adjacent to the foundation systems should be minimized.

Structural Considerations

Spread and Continuous Wall Foundations

It is understood that the proposed structure will be supported on conventional spread and continuous wall foundations. These foundations should be established on undisturbed native soils.

Under no circumstances shall footings be placed overlying non-engineered fills, loose soils, frozen soils, soil containing foreign debris, and any other deleterious material. Unsuitable material must be removed and replaced with an adequate structural fill as discussed in this report. For structural fill replacement beneath footings, the width of the structural fill shall be equal to width of the footing plus one foot on each side for each foot of fill thickness. For example, if the depth of structural fill is three feet then three feet of structural fill needs to extend past the edge of the footing on each side.

For design, the following parameters are provided:

Table 6 - Structural Design Parameters

Design Element Standard Recommended minimum depth of embedment for frost conditions 30-inches

Recommended minimum depth of embedment for non-frost conditions 15-inches

Recommended maximum bearing capacity of in-situ soil 2,000 pounds per square foot

Recommended width for continuous wall footings 18 to 30-inches

Recommended width for isolated spread footings 36 to 84-inches

Recommended bearing pressure increase for seismic loading 33%

Coefficient of friction between footing and native soils 0.35

Settlement of foundation elements are expected to be on the order of 1” or less with approximately 50% occurring during construction. This settlement can be expected if the project is constructed in accordance with recommendations found within this report.

Lateral Resistance

Passive resistance provided by properly placed and compacted native material fill above the water table may be considered to a fluid with a pressure of 375 pounds per cubic foot (Kp =3.0). Active resistance may be considered equivalent to a fluid with a pressure of 42 pounds per cubic foot (Ka = 0.33). Lateral earth pressure can be assumed to be much higher if material behind structural walls is not free draining. Passive and active resistance pressures will vary if groundwater is encountered. At this site, groundwater was encountered below the anticipated depth of foundations and therefore should not affect lateral resistance.

Walden Park Observatory Geotechnical Investigation 10 September 7, 2022

Floor slabs

Due to the intended use and anticipated loading, floor slabs should be constructed with a minimum of 4” of concrete (4,000 psi, air-entrained – 6% ± 1%) over 4" of clean gravel material. The subgrade material shall be properly prepared as discussed previously in this report. Under no circumstances should floor slabs be established over non-engineered fill, loose or disturbed soils, sod, rubbish, construction debris, other deleterious materials, frozen soils, or soils with ponded water. If constructed in accordance with this section, settlements of at-grade floor slabs supporting loads of 200 pounds per square foot should be on the order of ¼” or less.

Where appropriate, saw-cut control joints should be placed in the slab to help control the location and extent of cracking. For additional recommendations refer to the ACI Design Manual. Joints or any cracks that develop should be sealed with a water-proof, non-extruding compressible compound specifically recommended for heavy duty concrete pavement and wet environments.

The use of a vapor barrier should be considered beneath concrete slabs on grade that will be covered with wood, tile, carpet or other moisture sensitive or impervious coverings, or when the slab will support equipment sensitive to moisture. When conditions warrant the use of a vapor barrier, the slab designer should refer to ACI 302 and/or ACI 360 for procedures and cautions regarding the use and placement of a vapor barrier.

Soil Corrosiveness

The soil was sampled for sulfate levels at soil depths that will come into direct contact with the footings and foundations. These chemical levels are shown in Table 3 for reference.

Cement Use

Type I or IA mixes may be used in the design of these improvements. The soil tested contained a negligible amount of water-soluble sulfates. Based on our test results, concrete in contact with the in-situ soils will have a low potential for sulfate reaction and therefore the mix types of I or IA are acceptable. Other types of mixtures may be used by the design team if other strength/functionality parameters are desired.

Construction Considerations

On most project sites, the site grading is generally accomplished early in the construction phase.

However, as construction proceeds the subgrade may be disturbed due to utility excavations, construction traffic, desiccation, rainfall, etc. As a result, the floor slab or footing subgrade may not be suitable for placement of crushed gravel and concrete and corrective action will be required. We recommend areas underlying floor slabs and footings be rough graded and then thoroughly proof-rolled with a loaded tandem axle water or dump truck prior to final grading and placement of crushed gravel or concrete. Attention should be given to high traffic areas that were rutted and previously disturbed and to areas containing backfilled trenches. Areas where unsuitable conditions are located should be repaired by removing and replacing the affected material with properly compacted structural fill. All structural subgrade areas should be moisture conditioned and properly compacted to the recommendations in this report immediately prior to placement of the gravel and concrete.

Walden Park Observatory Geotechnical Investigation 11 September 7, 2022

Geoseismic Setting

Faulting

Based on a review of Utah Geological Survey fault maps, the site is approximately 6 miles west of the Utah Lake Faults, and approximately 15.5 miles west of the Wasatch Fault Line Provo Section.

Soil Class

The soil site class is D (S1 =0.269 g & SS = 0.741 g), with a Seismic Design Category D (Risk Category II) in accordance with Chapter 20 of ASCE 7 and IBC 2018.

Liquefaction

The site is in an area that has been classified as having very low liquefaction potential by the Utah Geological Survey. Liquefaction requires water, seismic activity, and loose sandy soils. Sandy soils and groundwater were not encountered in the field investigation. It is not anticipated that liquefaction will present a risk during a seismic event.

Groundwater

Immediately following drilling operations, the groundwater was measured in each boring. Seasonal and longer-term groundwater fluctuations on the order of one and one-half to three feet are projected, with the highest seasonal levels generally occurring during the late spring and early summer months. The groundwater measurements (as measured down from existing grade) are tabulated in Table 7 below:

Table 7 - Groundwater Depth

Bore Hole Number Time of Drilling (feet) B-1 Not Encountered

B-2 Not Encountered

B-3 Not Encountered

Closure Civil Solutions Group should be retained to provide observations during grading, excavation, foundation construction, and other earth-related construction activities related to this project. The conclusions and recommendations presented in this report are based on the results of the field and laboratory tests which, in our opinion, define the characteristics of the soils at this site in a satisfactory manner. However, this report does not reflect variations that may occur between borings, across the site, or due to the modifying effects of construction or weather. The nature and extent of such variations may not become evident until during or after construction. If during or after construction, conditions are encountered which appear to be different than those presented in this report, it is requested that our office be advised, in order that appropriate action be taken.

Our professional services have been performed, our findings obtained, and our recommendations prepared in accordance with generally accepted geotechnical engineering principles and practices.

Any persons using this report for bidding or construction purposes should perform independent investigations as they deem necessary to determine subsurface conditions. The scope of services for this project does not include either specifically or by implication any environmental or biological

Walden Park Observatory Geotechnical Investigation 12 September 7, 2022

(e.g., mold, fungi, bacteria) assessment of the site or identification or prevention of pollutants, hazardous materials or conditions. If the owner is concerned about the potential for such contamination or pollution, other studies should be undertaken.

This report has been prepared for the exclusive use of our client for specific application to the project discussed and has been prepared in accordance with generally accepted geotechnical engineering practices. No warranties, either express or implied, are intended or made. Site safety, excavation support, and dewatering requirements are the responsibility of others. If changes in the nature, design, or location of the project as outlined in this report are planned, the conclusions and recommendations contained in this report shall not be considered valid unless Civil Solutions Group reviews the changes and either verifies or modifies the conclusions of this report in writing.

Walden Park Observatory Geotechnical Investigation 13 September 7, 2022

Glossary/Explanation of Terms or Procedures

Throughout this report, we have used a number of words or phrases which may be unfamiliar in nature. Also, several procedural concepts have been mentioned repeatedly. For this reason, we have decided to define or discuss these items to better communicate with the reader(s).

Compaction and Lift Size - Contractors should be aware that there is direct relationship between lift size and size of the compacting equipment. The smaller the compactor, the smaller the maximum lift height. With “wacker” compactors, the maximum lift should be held at about 3-4-inches. With walk-behind trench compactors (2-tons or so), the lifts should be no more than 6-inches thick.

Eight-inch lifts can be used with large ride-on devices (7-10-tons or greater) that roll and vibrate/pound. Hoe pack devices on track hoes or backhoes can compact 6-8-inch lifts depending on size. However, the maximum lift size should not exceed 8-inches for most compactors. Note: a lift is defined as the loose or un-compacted thickness of the soil layer being compacted

Groundwater level - The groundwater level is a “rough guess” of where the uppermost water level is in a soil. We look for the first sign of free water coming in from the trench walls or appearing on the soil. In the soil logs, the groundwater level is identified by a solid or darkened triangle with a wavy line below it.

Liquefaction - Loss of bearing strength of saturated and very fine-grained silts and sands during severe earthquakes. This strength-loss is due to the slow dissipation of pore pressure (due to low permeability) and the subsequent reduction of particle-to-particle contact induced by the shaking motion of the earthquake.

Piezowater or Piezometer - To measure the groundwater level after a soil test pit is excavated, a pipe (a piezometer) is placed in the pit and left for at least 48-hours. The bottom 12-inches of the piezometer is slotted and capped to keep soil from entering and plugging up the pipe. The piezometer is then backfilled. After 48-hours, the water level in the piezometer is recorded. This level is the piezowater level. It is often higher than the point where water is first seen in a test pit during excavation. The importance is that the piezometer level is the potential depth of the groundwater for a site location should a ‘dig’ be done at the site. However, this level may change over time depending on weather conditions (wet or dry years and periods); rust or mottling of the soils may indicate an historical level of the water. In the soil logs, the piezowater level is a line with an “open” triangle above it and a wavy line below the triangle. The “open” triangle signifies the fact that the overlying soil “cap” has been removed.

Topsoil - It is generally defined as surface soils (silts or clays) with greater than 2-percent organics;

this soil is often dark brown to black in color. It generally has visible roots or organic matter and is highly compressible. Topsoil should never be used under a footing or load bearing structure; it is generally, too compressible and with loading, settles over time. It should be stockpiled for use in landscaped areas, used for wetland mitigation/re-seeding, as a pond liner, or exported from the site.

Undisturbed soil - This is soil in its natural state, undisturbed by past excavation, farming, construction, or perturbation of any type. It is a most important feature. Areas that have been filled are always considered disturbed. On the other hand, “cut” areas can be considered undisturbed if the soil was cut with a straight bladed bucket edge, and not tines. If soils are disturbed, and footings or walls will be bear on these soils, they must be re-compacted.

Walden Park Observatory Geotechnical Investigation 14 September 7, 2022

Non-Engineered Fill – Non-engineered fill material is non-native (imported) material that has not been tested in the lab for engineering properties nor has a record of proper placement and compaction. Therefore, it should not be used for structural fill. This material can be used if properly prepared, but Civil Solutions Group recommends any non-engineered material in which loads will bear on be tested prior to placement. Once placed, this material should be tested to ensure structural properties are met. Recommendations in this report are based upon the materials encountered during the field investigation.

Walden Park Observatory Geotechnical Investigation 15 September 7, 2022

Appendix

Figure 1 - Vicinity Map

Walden Park Observatory Geotechnical Investigation 16 September 7, 2022

Figure 2 - Site Map

Walden Park Observatory Geotechnical Investigation 17 September 7, 2022

Figure 3 - Looking West

Figure 4 – Looking South

Walden Park Observatory Geotechnical Investigation 18 September 7, 2022

Figure 5 – Key to Soil Logs

D ep th

Lithologic Description

Ground Surface EL 0 ft _Topsoil _with roots

Top Soil 0.5 ft EL -0.5 ft

_Low _Plasticity _Silt _With _Sand, ML dry, brown, stiff

5.5 ft EL -5.5 ft

_Low _Plasticity _Clay _With _Sand, CL dry to moist, brown, soft to medium stiff

Sy m bo l Sa m pl es

No.

Ty pe

1.1 SS

1.2 SS

1.3 SS

1.4 TS

1.5 SS

1.6 SS

1.7 SS

Gradation (%)

Gravel Sand Fines

0 15

0 1

0 3

A tte rb er g Li m its

LL

PL

35 16

38 23

M oi st ur e

13.7

25.9

33.8

B lo w C ou nt

Standard Penetration Test

(SPT)

BORE LOG: B-1

NOTES:

Frontier street American way, Eagle Mountain, UT

LONGITUDE:-112.00632

LATITUDE: 40.3095

ELEVATION:

ADDRESS:LOGGED BY: REVIEWER:AM JP

DATE: August 17, 2022

Eagle Mountain Observatory 22-211

Eagle Mountain City

SHEET:

PROJECT TITLE:

CLIENT:

PROJECT NO.:

th

Lithologic Description

(continued) _Low _Plasticity _Clay _With _Sand, CL dry to moist, brown, soft to medium stiff 25.5 ft EL -25.5 ft

End of Test Hole at 25.5 (ft)

Sy m bo l Sa m pl es

No.

Ty pe

1.7 SS

Gradation (%)

Gravel Sand Fines

A tte rb er g Li m its

LL

PL

) M oi st ur e

B lo w C ou nt

Standard Penetration Test

(SPT)

BORE LOG: B-1

NOTES:

Frontier street American way, Eagle Mountain, UT

LONGITUDE:-112.00632

LATITUDE: 40.3095

ELEVATION:

ADDRESS:LOGGED BY: REVIEWER:AM JP

DATE: August 17, 2022

Eagle Mountain Observatory 22-211

Eagle Mountain City

SHEET:

PROJECT TITLE:

CLIENT:

PROJECT NO.:

th

Lithologic Description

Ground Surface EL 0 ft _Topsoil _with roots

Top Soil 0.5 ft EL -0.5 ft

_Low _Plasticity _Silt _With _Sand, ML dry, brown, very stiff to stiff

5 ft EL -5 ft

_Low _Plasticity _Clay _With _Sand, CL dry to moist, brown, soft to stiff

20.5 ft EL -20.5 ft

End of Test Hole at 20.5 (ft)

Sy m bo l Sa m pl es

No.

Ty pe

2.1 SS

2.2 SS

2.3 SS

2.4 SS

2.5 SS

2.6 SS

Gradation (%)

Gravel Sand Fines

0 15

A tte rb er g Li m its

LL

PL

21 13

M oi st ur e

16.0

B lo w C ou nt

Standard Penetration Test

(SPT)

BORE LOG: B-2

NOTES:

Frontier street American way, Eagle Mountain, UT

LONGITUDE:-112.00683

LATITUDE: 40.30948

ELEVATION:

ADDRESS:LOGGED BY: REVIEWER:AM JP

DATE: August 17, 2022

Eagle Mountain Observatory 22-211

Eagle Mountain City

SHEET:

PROJECT TITLE:

CLIENT:

th

Lithologic Description

Ground Surface EL 0 ft _Topsoil _with roots

Top Soil 0.5 ft EL -0.5 ft

_Low _Plasticity _Silt _With _Sand, ML dry, brown, medium stiff

6 ft EL -6 ft

_Low _Plasticity _Clay _With _Sand, CL dry to moist, brown, medium stiff

15.5 ft EL -15.5 ft

End of Test Hole at 15.5 (ft)

Sy m bo l Sa m pl es

No.

Ty pe

3.1 SS

3.2 SS

3.3 SS

Gradation (%)

Gravel Sand Fines

A tte rb er g Li m its

LL

PL

) M oi st ur e

B lo w C ou nt

Standard Penetration Test

(SPT)

BORE LOG: B-3

NOTES:

Frontier street American way, Eagle Mountain, UT

LONGITUDE:-112.00632

LATITUDE: 40.30919

ELEVATION:

ADDRESS:LOGGED BY: REVIEWER:AM JP

DATE: August 17, 2022

Eagle Mountain Observatory 22-211

Eagle Mountain City

SHEET:

PROJECT TITLE:

CLIENT: