Report Cover Page

Storey Boulevard

Extension Geotechnical Engineering Report

April 25, 2023 | Terracon Project No. 24235022

Prepared for:

AVI PC

1103 Old Town Lane, Suite 101

Cheyenne, Wyoming 82009

1505 Old Happy Jack Road

Cheyenne, Wyoming 82001

P (307) 638-5263

Terracon.com

Facilities | Environmental | Geotechnical | Materials

Report Cover Letter to Sign

April 25, 2023

AVI PC

1103 Old Town Lane, Suite 101

Cheyenne, Wyoming 82009

Attn: Tristan D. Cordier, P.E.

P: (307) 637-6017

E: tcordier@avipc.com

Re: Geotechnical Engineering Report

Storey Boulevard Extension

Storey Boulevard

Cheyenne, Wyoming

Terracon Project No. 24235022

Dear Mr. Cordier:

We have completed the scope of Geotechnical Engineering services for the project referenced above in general accordance with Terracon Proposal No. P24235022 dated

February 28, 2023. This report presents the findings of the subsurface exploration and provides geotechnical recommendations concerning pavements and earthwork for the proposed project.

We appreciate the opportunity to be of service to you on this project. If you have any questions concerning this report or if we may be of further service, please contact us.

Sincerely, Terracon

Cindy E. Rodriguez Hernandez Eric D. Bernhardt, P.E.

Project Geologist Senior Associate

Storey Boulevard Extension | Cheyenne, Wyoming

Facilities | Environmental | Geotechnical | Materials i

Table of Contents Report Summary .............................................................................................. i

Introduction

Project Description

Site Conditions

Geotechnical Characterization

Groundwater

Corrosivity

Geotechnical Overview

Earthwork

Existing Fill

Site Preparation

Subgrade Preparation

Excavation

Soil Stabilization

Fill Material Types

Fill Placement and Compaction Requirements

Utility Trench Backfill

Drainage

Earthwork Construction Considerations

Construction Observation and Testing

Pavements

Subgrade Preparation

General Pavement Comments

Pavement Design Parameters

Pavement Section Thicknesses

Pavement Drainage

Pavement Maintenance

General Comments

Figures GeoModel

Attachments

Exploration and Testing Procedures Site Location and Exploration Plans

Exploration and Laboratory Results

Supporting Information

Facilities | Environmental | Geotechnical | Materials ii

Note: This report was originally delivered in a web-based format. Blue Bold text in the report indicates a referenced section heading. The PDF version also includes hyperlinks which direct the reader to that section and clicking on the logo will bring you back to this page. For more interactive features, please view your project online at client.terracon.com.

Refer to each individual Attachment for a listing of contents.

http://client.terracon.com/

Facilities | Environmental | Geotechnical | Materials i

Report Summary

Topic Overview Statement

Project Description

The project consists of an extension of the existing Storey

Boulevard. The extension alignment is planned to run from North

College Drive to Whitney Road with a total length of approximately 1.5 miles.

Geotechnical Characterization

Subsurface conditions encountered in the borings consisted of silty clayey sand, clayey sand, and/or sandy lean clay. Existing undocumented fill was observed in out exploratory borings extending to depths ranging from about 1 to 3 feet below grade in

Borings B-01 through B-06 and B-13 through B-16. Groundwater was not encountered during the time of the drilling.

Earthwork

Existing undocumented fill was encountered at depths of up to 3 feet and should be removed or remediated prior to roadway construction.

Pavements

With subgrade prepared as noted in Earthwork.

Asphalt Concrete (AC):

■ 8” AC over 10” granular base course

■ 6” AC over 12” granular base course

Portland Cement Concrete (PCC):

■ 8” PCC

General Comments

This section contains important information about the limitations of this geotechnical engineering report.

1. If the reader is reviewing this report as a pdf, the topics above can be used to access the appropriate section of the report by simply clicking on the topic itself.

2. This summary is for convenience only. It should be used in conjunction with the entire report for design purposes.

Facilities | Environmental | Geotechnical | Materials 1

Introduction

This report presents the results of our subsurface exploration and Geotechnical

Engineering services performed for the proposed road extension to be located along

Storey Boulevard from College Drive to Whitney Road in Cheyenne, Wyoming. The purpose of these services were to provide information and geotechnical engineering recommendations relative to:

■ Subsurface soil conditions

■ Groundwater conditions

■ Site preparation and earthwork

■ Demolition considerations

■ Pavement design and construction

The geotechnical engineering Scope of Services for this project included the advancement of test borings, laboratory testing, engineering analysis, and preparation of this report.

Drawings showing the site and boring locations are shown on the Site Location and

Exploration Plan, respectively. The results of the laboratory testing performed on soil samples obtained from the site during our field exploration are included on the boring logs in the Exploration Results section.

Project Description

Our initial understanding of the project was provided in our proposal and was discussed during project planning. A period of collaboration has transpired since the project was initiated, and our final understanding of the project conditions is as follows:

Item Description

Information

Provided

This report is based on information provided by Tristan Cordier and Andrew Bartel of AVI via emails on February 13 through

March 27, 2023. Provided documents included:

■ Storey Bore Hole Exhibit prepared by AVI dated February

10, 2023

■ Estimated traffic counts.

Facilities | Environmental | Geotechnical | Materials 2

Item Description

Project

Description

The project consists of an extension of the existing Storey

Boulevard. The extension alignment is planned to run from

North College Drive to Whitney Road with a total length of approximately 1.5 miles. Based on the provided traffic counts, the proposed extension road will classify as a minor arterial roadway.

Grading/Slopes

We assume the proposed street grade will generally match the existing topography. Based on the anticipated topography along the planned project alignment, our boring depths were developed under the assumption of planned cuts/fills of about 1 to 5 feet may be required to achieve final enhancement and subgrade elevations.

Pavements We understand flexible (asphalt), and rigid (PCC) pavement sections are being considered this project.

Terracon should be notified if any of the above information is inconsistent with the planned construction, especially the grading limits, as modifications to our recommendations may be necessary.

Site Conditions

The following description of site conditions is derived from our site visit in association with the field exploration and our review of publicly available geologic and topographic maps.

Item Description

Parcel

Information

The project alignment extends Storey Boulevard east from North

College Drive to Whitney Road in Cheyenne, Wyoming. The approximate coordinates for the planned improvements are as follows:

North College Drive and Storey Boulevard

■ 41.1744° N, 104.7614° W

Whitney Road and Storey Boulevard

■ 41.1744° N, 104.7322° W

See Site Location

Facilities | Environmental | Geotechnical | Materials 3

Existing

Improvements

The general area adjacent to the proposed project alignment appears to consist of widely-spread residential properties. The proposed alignment areas between North College Drive and

Highland Road and Robert Parker Trail to Whitney Road are existing aggregate-surfaced roadways. The proposed alignment area between Highland Road and Robert Parker Trail is unpaved, vacant land.

Current Ground

Cover

The current ground cover along the planned alignment is aggregated-surfaced and/or undeveloped land with variety of vegetation.

Existing

Topography

The area along the proposed street improvements appears to be generally flat from North College Drive to Van Buren Avenue;

topography along Van Buren Avenue to Whitney Road consists of rolling hills with an approximate elevation difference of about 60 feet.

Geotechnical Characterization

We have developed a general characterization of the subsurface conditions based upon our review of the subsurface exploration, laboratory data, geologic setting and our understanding of the project. This characterization, termed GeoModel, forms the basis of our geotechnical calculations and evaluation of the site. Conditions observed at each exploration point are indicated on the individual logs. The individual logs can be found in the Exploration Results and the GeoModel can be found in the Figures attachment of this report.

As part of our analyses, we identified the following model layers within the subsurface profile. For a more detailed view of the model layer depths at each boring location, refer to the GeoModel.

Model

Layer Layer Name General Description

1 Vegetative Soil Vegetative soil was observed in borings B-07 to B-12 at about 6 inches thick

2 Existing Fill

Existing fill encountered in borings B-01 through B-

06 and B-13 through B16 from about 1 to 3 feet below grade consisting of sand with varying amounts of clay, silty and gravel

Silty Clayey

Sand

Silty clayey sand, fine to coarse grained sand, with gravel and/or cobbles, very loose to medium dense

Facilities | Environmental | Geotechnical | Materials 4

Model

Layer Layer Name General Description

4 Clayey Sand Clayey sand, fine to coarse grained, trace gravel, loose to very dense

5 Sandy Lean Clay Sandy lean clay, fine grained sand, tan to brown, stiff to hard, calcareous lenses

Groundwater

The borings were advanced in the dry using an air rotary drilling technique that allow short term groundwater observations to be made while drilling. Groundwater seepage was not encountered within the maximum drilling depth at the time of our field exploration. Groundwater level fluctuations occur due to seasonal variations in the amount of rainfall, runoff, irrigation, and other factors not evident at the time the borings were performed. Therefore, groundwater levels during construction or excavations may be higher or lower. However, we do not believe groundwater will significantly impact the proposed construction.

Corrosivity

The table below lists the results of laboratory pH, soluble sulfate, sulfides, soluble chloride, Redox potential, total salts, and electrical resistivity testing. The values may be used to estimate potential corrosive characteristics of the on-site soils with respect to contact with the various underground materials which will be used for project construction.

Corrosivity Test Results Summary

Boring

Sample

Depth

(feet)

Soil

Description pH

Soluble

Sulfate

(mg/kg)

Sulfides

(mg/kg)

Chlorides

(mg/kg) RedOx

Total

Salts

(mg/kg)

Electrical

Resistivity

(Ω-cm)

B-7 0-6 SC 8.0 47 0 186 +317 2.1 1,220

1. Laboratory electrical resistivity testing was performed on a saturated sample.

Results of water-soluble sulfate testing indicate the sample of the on-site soils has an exposure class of S0 when classified in accordance with Table 19.3.1.1 of the American

Concrete Institute (ACI) Design Manual. Therefore, Type I portland cement should be suitable for concrete on and below grade. However, if there is no, or minimal cost differential, use of Type II portland cement (or equivalent) should be considered for additional sulfate resistance of construction concrete. Concrete should be designed in accordance with the provisions of the ACI Design Manual, Section 318, Chapter 19.

Facilities | Environmental | Geotechnical | Materials 5

Resistivity test results lower than 2,000 ohm-cm indicate very corrosive conditions for buried metal. These test results are provided to assist in determining the type and degree of corrosion protection that may be required. A corrosion engineer could be retained to provide additional corrosion protection recommendations.

Geotechnical Overview

The site appears suitable for the proposed construction based upon geotechnical conditions encountered in the test borings, provided the recommendations provided in this report are implemented in the design and construction phases of this project.

The subsurface materials generally consisted of sand with varying amounts of clay and silt. Undocumented existing fill was observed in Borings B-01 through B-06 and B-13 through B-16 which are in areas of the existing aggregate surfaced road. It is unclear if fill will be encountered at deeper depths or other locations. We recommend thoroughly proof-rolling the prepared subgrade prior to placing aggregate base course and/or pavement materials.

Support of pavements on or above existing fill materials is discussed in this report.

However, even with the recommended construction procedures, an inherent risk remains for the owner that compressible fill or unsuitable material, within or buried by the fill, will not be discovered. This risk of unforeseen conditions cannot be eliminated without completely removing the existing fill but can be reduced by the following the recommendations contained in this report. To take advantage of the cost benefit of not removing the entire amount of undocumented fill below pavements, the owner must be willing to accept the risk of increased differential performance, which can result in increased cracking and abrupt differential settlement. Should this risk be acceptable, pavements can be supported above the fill.

The recommendations contained in this report are based upon the results of field and laboratory testing (presented in the Exploration Results), engineering analyses, and our current understanding of the proposed project. The General Comments section provides an understanding of the report limitations.

Earthwork

Earthwork is anticipated to include clearing and grubbing, excavations, and engineered fill placement. The following sections provide recommendations for use in the preparation of specifications for the work. Recommendations include critical quality criteria, as necessary, to render the site in the state considered in our geotechnical engineering evaluation for pavements.

Facilities | Environmental | Geotechnical | Materials 6

Existing Fill

As noted in Geotechnical Characterization, borings B-01 through B-06 and B-13 through B-16 encountered previously placed fill to depths ranging from about 1 to 3 feet below grade. Existing fill may exist in other areas of the site and could possibility extend to greater depths. We have no records to indicate the degree of control. This risk of unforeseen conditions cannot be eliminated without completely removing the existing fill but can be reduced by following the recommendations contained in this report. Support of pavements on or above existing fill soils is discussed in this report.

Given the apparent surficial nature of existing fills and the anticipated traffic volumes, consideration could be given to supporting pavements on a minimum of 12 inches of scarified, moisture conditioned and recompacted fill materials provided some risk of pavement settlement can be accepted. If the client cannot accept the risk of pavement settlements, existing fill materials encountered below proposed pavement areas should be completely removed and re-compacted or replaced prior to placement of aggregate base course material.

Terracon’s services did not include delineating the horizontal or vertical extent of the existing fill material. Additional geotechnical exploration and evaluation could be conducted at the site prior to construction. We believe a series of backhoe test pits/trenches could be excavated on the site to more accurately define the vertical and lateral extent of the fill materials and the composition of the fill.

Site Preparation

Prior to placing fill, existing vegetation, topsoil, and root mats should be removed.

Complete stripping of the topsoil should be performed in the proposed building and parking/driveway areas.

Stripped organic materials, if any, should be wasted from the site or used to re-vegetate landscaped areas or exposed slopes after completion of grading operations. The soil materials which contain less than 5 percent organics can be reused as engineered fill provided the material is moisture conditioned and properly compacted. Prior to the placement of fills, the site should be graded to create relatively level surface to receive fill, and to provide for a relatively uniform thickness of fill beneath proposed construction.

Where fill is placed on existing slopes steeper than 5H:1V, benches should be cut into the existing slopes prior to fill placement. The benches should have a minimum vertical face height of 1 foot and a maximum vertical face height of 3 feet and should be cut wide enough to accommodate the compaction equipment. This benching will help provide a positive bond between the fill and natural soils and reduce the possibility of failure along the fill/natural soil interface.

Facilities | Environmental | Geotechnical | Materials 7

Subgrade Preparation

On-site soils are considered suitable to be used as Engineered Fill materials, provided all existing and undocumented fill has been remediated as necessary prior to the state of construction.

The subgrade should be proofrolled with an adequately loaded vehicle such as a fully-loaded tandem-axle dump truck. The proofrolling should be performed under the observation of the Geotechnical Engineer or representative. Areas excessively deflecting under the proofroll should be delineated and subsequently addressed by the

Geotechnical Engineer.

All exposed areas which will receive fill, once properly cleared and benched where necessary, should be scarified to a minimum depth of 10 inches, moisture conditioned as necessary, and compacted per the compaction requirements in this report. Compacted engineered fill soils should then be placed to the proposed design grade and the moisture content and compaction of subgrade soils should be maintained until pavement construction.

Based upon the subsurface conditions determined from the geotechnical exploration, subgrade soils exposed during construction are anticipated to be relatively workable;

however, the workability of the subgrade may be affected by precipitation, repetitive construction traffic or other factors. If unworkable conditions develop, workability may be improved by scarifying and drying.

Excavation

We anticipate excavations for the proposed construction can be accomplished with conventional earthmoving equipment. The means and methods for excavation should be evaluated and determined by the earthwork contractor.

The soils to be excavated can vary significantly across the site as their classifications are based solely on the materials encountered in widely-spaced exploratory test borings.

The contractor should verify that similar conditions exist throughout the proposed area of excavation. If different subsurface conditions are encountered at the time of construction, the actual conditions should be evaluated to determine any excavation modifications necessary to maintain safe conditions.

Although evidence of underground facilities such as utilities were not observed during the site reconnaissance, such features could be encountered during construction. If unexpected underground facilities are encountered, such features should be removed, and the excavation thoroughly cleaned prior to backfill placement and/or construction.

Facilities | Environmental | Geotechnical | Materials 8

As a minimum, excavations should be performed in accordance with OSHA 29 CFR, Part

1926, Subpart P, “Excavations” and its appendices, and in accordance with any applicable local and/or state regulations.

As a safety measure, it is recommended that all vehicles and soil piles be kept a minimum lateral distance from the crest of the slope equal to the slope height. The exposed slope face should be protected against the elements.

Soil Stabilization

Methods of subgrade improvement, as described below, could include scarification, moisture conditioning and recompaction, removal of unstable materials and replacement with granular fill (with or without geosynthetics), and chemical stabilization. The appropriate method of improvement, if required, would be dependent on factors such as schedule, weather, the size of area to be stabilized, and the nature of the instability.

More detailed recommendations can be provided during construction as the need for subgrade stabilization occurs. Performing site grading operations during warm seasons and dry periods would help reduce the amount of subgrade stabilization required.

If the exposed subgrade is unstable during proofrolling operations, it could be stabilized using one of the methods outlined below.

■ Scarification and Recompaction - It may be feasible to scarify, dry, and recompact the exposed soils. The success of this procedure would depend primarily upon favorable weather and sufficient time to dry the soils. Stable subgrades likely would not be achievable if the thickness of the unstable soil is greater than about 1 foot, if the unstable soil is at or near groundwater levels, or if construction is performed during a period of wet or cool weather when drying is difficult.

■ Crushed Stone - The use of crushed stone or crushed gravel is a common procedure to improve subgrade stability. Typical undercut depths would be expected to range from about 12 to 18 inches below finished subgrade elevation.

The use of high modulus geotextiles (i.e., engineering fabric or geogrid) could also be considered after underground work such as utility construction is completed. Prior to placing the fabric or geogrid, we recommend that all below grade construction, such as utility line installation, be completed to avoid damaging the fabric or geogrid. Equipment should not be operated above the fabric or geogrid until one full lift of crushed stone fill is placed above it. The maximum particle size of granular material placed over geotextile fabric or geogrid should not exceed 1-1/2 inches.

■ Chemical Modification - Improvement of subgrades with portland cement or

Class C fly ash could be considered for improving unstable soils. Chemical modification should be performed by a pre-qualified contractor having experience

Facilities | Environmental | Geotechnical | Materials 9 with successfully stabilizing subgrades in the project area on similar sized projects with similar soil conditions. Results of chemical analysis of the additive materials should be provided to the geotechnical engineer prior to use. The hazards of chemicals blowing across the site or onto adjacent property should also be considered. Additional testing would be needed to develop specific recommendations to improve subgrade stability by blending chemicals with the site soils. Additional testing could include, but not be limited to, determining the most suitable stabilizing agent, the optimum amounts required, the presence of sulfates in the soil, and freeze-thaw durability of the subgrade.

Further evaluation of the need and recommendations for subgrade stabilization can be provided during construction as the geotechnical conditions are exposed.

Fill Material Types

Fill for this project should consist of engineered fill. Engineered fill is fill that meets the criteria presented in this report and has been properly documented. On-site soils or approved granular and low plasticity cohesive imported materials may be used as fill material. Imported materials meeting the properties presented below should be acceptable for use as engineered fill. However, imported soils should be evaluated and approved by the geotechnical engineer prior to delivery to the site.

Gradation/Property Percent Finer by Weight

(ASTM C136/D422)

3-inch 100

No. 4 Sieve 30 to 100

No. 200 Sieve 15 to 60

Soil Properties Values

Liquid Limit (LL) 30 (max.)

Plasticity Index (PI) 15 (max.)

Aggregate base course used for roadways and parking areas should meet WYDOT requirements for Grading L or W aggregate base course materials.

Other import fill material types may be suitable for use depending upon proposed application and location on the site and should be tested and approved for use on a case-by-case basis.

Fill Placement and Compaction Requirements

Placement of engineered fill should meet the following compaction requirements.

Facilities | Environmental | Geotechnical | Materials 10

Maximum Lift

Thickness

■ 8 inches or less in loose thickness when heavy, self-propelled compaction equipment is used

■ 4 to 6 inches in loose thickness when hand-guided equipment (i.e. jumping jack or plate compactor) is used

Minimum

Compaction

Requirements 1,2

■ At least 95% of the standard Proctor maximum dry density

(AASHTO T99)

Water Content

Range 3,4

■ Clay soils: -1% to +3% of the optimum moisture content as determined by the standard Proctor test (AASHTO T99)

■ Granular soils: -4% to +2% of the optimum moisture content as determined by the standard Proctor test

(AASHTO T99)

1. Structural and general fill should be placed and compacted in horizontal lifts, using the equipment and procedures that will produce recommended moisture contents and densities throughout the lift. A construction disc or other suitable processing equipment will be needed to thoroughly process the materials and to aid in achieving uniform moisture content throughout the fill.

2. The contractor should expect significant moisture adjustment and processing of the site soils or import materials will be needed prior to or during compaction operations.

3. Moisture conditioned cohesive soils (lean clay) should not be allowed to dry out. A loss of moisture within these materials will likely result in an increase of the material’s well potential. Subsequent wetting of these materials could results in undesirable movements.

4. Care should be taken during the fill placement process to avoid zones of dissimilar fill.

Improvements constructed over varying fill types are at a higher risk of differential movement compared to improvements over a uniform fill zone.

Utility Trench Backfill

Any soft or unsuitable materials encountered at the bottom of utility trench excavations should be removed and replaced with structural fill or bedding material in accordance with public works specifications for the utility be supported. This recommendation is particularly applicable to utility work requiring grade control and/or in areas where subsequent grade raising could cause settlement in the subgrade supporting the utility.

On-site materials are considered suitable for backfill of utility and pipe trenches from 1 foot above the top of the pipe to the final ground surface, provided the material is free of organic matter and deleterious substances.

Trench backfill should be mechanically placed and compacted as discussed earlier in this report. Compaction of initial lifts should be accomplished with hand-operated tampers or

Facilities | Environmental | Geotechnical | Materials 11 other lightweight compactors. Flooding or jetting for placement and compaction of backfill is not recommended.

Drainage

To maintain and enhance the long-term performance of the pavement sections, it is imperative to design and construct the roadways with a crown or slope to facilitate positive surface drainage away from the pavement and to the adjacent ditch lines. Water on or adjacent to the pavements can saturate the subgrade and contribute to premature pavement deterioration. In addition, the pavement subgrade should be graded to provide positive drainage with the granular base section. The roadway shoulders should be sloped to the ditch lines to preclude water ponding adjacent to the pavement.

Earthwork Construction Considerations

Upon completion of filling and grading, care should be taken to maintain the subgrade water content prior to construction of grade-supported improvements. Construction traffic over the completed subgrades should be avoided. The site should also be graded to prevent ponding of surface water on the prepared subgrades or in excavations. Water collecting over or adjacent to construction areas should be removed. If the subgrade freezes, desiccates, saturates, or is disturbed, the affected material should be removed, or the materials should be scarified, moisture conditioned, and recompacted prior to floor slab construction.

Construction site safety is the sole responsibility of the contractor who controls the means, methods, and sequencing of construction operations. Under no circumstances shall the information provided herein be interpreted to mean Terracon is assuming responsibility for construction site safety or the contractor's activities; such responsibility shall neither be implied nor inferred.

Construction Observation and Testing

The earthwork efforts should be observed by the Geotechnical Engineer (or others under their direction). Observation should include documentation of adequate removal of surficial materials (vegetation, topsoil, and pavements), evaluation and remediation of existing fill materials, as well as proofrolling and mitigation of unsuitable areas delineated by the proofroll.

Each lift of compacted fill should be tested, evaluated, and reworked, as necessary, as recommended by the Geotechnical Engineer prior to placement of additional lifts. Each lift of fill should be tested for density and water content at a frequency of at least one test for every 5,000 square feet in pavement areas. Where not specified by local ordinance, one density and water content test should be performed for every 100 linear

Facilities | Environmental | Geotechnical | Materials 12 feet of compacted utility trench backfill (if any) and a minimum of one test performed for every 12 vertical inches of compacted backfill.

In addition to the documentation of the essential parameters necessary for construction, the continuation of the Geotechnical Engineer into the construction phase of the project provides the continuity to maintain the Geotechnical Engineer’s evaluation of subsurface conditions, including assessing variations and associated design changes.

Pavements

Subgrade Preparation

As discussed above, undocumented fill was encountered to depths of up to 3.0 feet below existing grades. Given the apparent surficial nature of existing fills and the anticipated traffic volumes, consideration could be given to supporting pavements on a minimum of 12 inches of scarified, moisture conditioned and recompacted fill materials provided some risk of pavement settlement can be accepted. The subgrade should then be proofrolled to help delineate weak or disturbed areas. Unsuitable areas should be improved by moisture adjustment and compaction or by undercutting and placement of suitable compacted fill.

The placement of engineered fill to desired grade should be performed in accordance with the Earthwork section of this report. We recommend the moisture content and density of the top 12 inches of pavement subgrade be evaluated shortly before actual paving operations. Areas not in compliance with the required ranges of moisture or density as listed in this report should be moisture conditioned and re-compacted.

Particular attention should be paid to high traffic areas that were rutted and disturbed earlier and to areas where backfilled trenches are located.

General Pavement Comments

Pavement designs are provided for the traffic conditions and pavement life conditions as noted in Project Description and in the following sections of this report. A critical aspect of pavement performance is site preparation. Pavement designs noted in this section must be applied to the site which has been prepared as recommended in the

Earthwork section.

Support characteristics of subgrade for pavement design do not account for shrink/swell movements of an expansive clay subgrade. Thus, the pavement may be adequate from a structural standpoint, yet still experience cracking and deformation due to shrink/swell related movement of the subgrade.

Facilities | Environmental | Geotechnical | Materials 13

Pavement Design Parameters

Composite bulk samples of on-site soils were obtained from borings and stockpile (SP) and tested for laboratory R-value. The following table presents the results of our laboratory R-value test:

Sample ID Bulk Soil

Classification R-value (calculated)

California

Bearing Ratio

(Correlated)

SP Silty, Clayey Sand 27 4

B-10 Silty Clayey Sand and

Clayey San

A California Bearing Ratio (CBR) of 4.0 was used for the subgrade for the asphaltic concrete (AC) pavement designs. A modulus of subgrade reaction of 125 pci was used for the portland cement concrete (PCC) pavement designs. The modulus of subgrade reaction value was determined by correlation to the laboratory R-value tests and is present in the R-value table above. A modulus of rupture of 580 psi was used in design for the concrete (based on correlations with a minimum 28-day compressive strength of

4,000 psi).

Design Criteria Value

Daily Traffic Volume

Cars

Trucks

7,448

Estimated Growth Factor Percentage 2

Estimated ESALs 2,546,413

Pavement Thickness Design Parameters

Input Parameter Value

Reliability 85%

Serviceability Loss 2.5

Standard Deviation

0.44

Asphalt Layer Coefficient

0.44

Aggregate Base Coefficient 0.12

Design Subgrade Resilient Modulus 5,500

Facilities | Environmental | Geotechnical | Materials 14

Pavement Section Thicknesses

The following table provides our opinion of minimum thickness for AC sections:

Asphaltic Concrete Design

Layer Thickness (inches)

Minor Arterial

Asphaltic Concrete

Surface 1 8 6

Aggregate Base 2 10 12

Total Thickness 18 18

1. Asphalt Concrete (AC) should be composed of mixture of aggregate, filler and additives, if required, and approved bituminous material. AC should conform to approve mix designs stating the Superpave or Marshall properties, optimum asphalt content, job mix formula and recommended mixing and placing temperatures. Aggregate used in plant-mixed AC should meet particular gradations. Material meeting ¾“ or ½“ nominal maximum size specifications is recommended for AC.

2. Aggregate base course (ABC) should consist of a blend of sand and gravel which meets strict specifications for quality and gradation and should have a R-value of at least 75.

Use of materials meeting Wyoming Department of Transportation (WYDOT) Grading W or L specification is recommended. ABC should be placed in maximum 6-inch lifts and compacted to at least 95% of the standard Proctor maximum dry density (AASHTO T99).

The following table provides our estimated minimum thickness of PCC pavements.

Portland Cement Concrete Design

Layer Thickness (inches)

Minor Arterial

PCC 1 8

1. All materials should meet the current Cheyenne specifications and/or Wyoming

Department of Transportation (WDOT) standard specifications for road construction.

Areas for parking of heavy vehicles, concentrated turn areas, and start/stop maneuvers could require thicker pavement sections. Edge restraints (i.e. concrete curbs or aggregate shoulders) should be planned along curves and areas of maneuvering vehicles.

Where practical, we recommend early-entry cutting of crack-control joints in PCC pavements. Cutting of the concrete in its “green” state typically reduces the potential for

Facilities | Environmental | Geotechnical | Materials 15 micro-cracking of the pavements prior to the crack control joints being formed, compared to cutting the joints after the concrete has fully set. Micro-cracking of pavements may lead to crack formation in locations other than the sawed joints, and/or reduction of fatigue life of the pavement.

Openings in pavements, such as decorative landscaped areas, are sources for water infiltration into surrounding pavement systems. Water can collect in the islands and migrate into the surrounding subgrade soils thereby degrading support of the pavement.

Islands with raised concrete curbs, irrigated foliage, and low permeability near-surface soils are particular areas of concern. The civil design for the pavements with these conditions should include features to restrict or collect and discharge excess water from the islands. Examples of features are edge drains connected to the stormwater collection system, longitudinal subdrains, or other suitable outlets and impermeable barriers preventing lateral migration of water such as a cutoff wall installed to a depth below the pavement structure.

Pavement Drainage

Pavements should be sloped to provide rapid drainage of surface water. Water allowed to pond on or adjacent to the pavements could saturate the subgrade and contribute to premature pavement deterioration. In addition, the pavement subgrade should be graded to provide positive drainage within the granular base section. Appropriate sub-drainage or connection to a suitable daylight outlet should be provided to remove water from the granular subbase.

Based on the possibility of shallow and/or perched groundwater, we recommend installing a pavement subdrain system to control groundwater, improve stability, and improve long-term pavement performance.

Due to frost-susceptible soils and the possibility of perched groundwater, consideration should be given to installing a pavement subdrain system to control subgrade moisture, improve stability, and improve long-term pavement performance.

If selected, we recommend at least 6 inches of free-draining granular material be placed beneath the pavements. The use of a free draining granular base will also reduce the potential for frost action. We recommend pavement subgrades be crowned at least 2% to promote the flow of water towards the subdrains, and to reduce the potential for ponding of water on the subgrade. The design recommendations for the subdrains are provided in the following table:

Facilities | Environmental | Geotechnical | Materials 16

Subdrain Design Recommendations

Item Value

Free Draining Granular Base

Thickness below Pavement

6 inches of material meeting No. 57 aggregate specifications

Minimum Drainpipe Diameter 4 inches

Drain Trench Width

16 inches or greater to provide minimum

6-inch annulus of drainage aggregate around drainpipe.

Invert Depth below Subgrade

Elevation 3½ feet

Maximum Drainpipe Spacing 50 feet

Subdrain Trench Backfill Material No. 57 aggregate or ¾-inch aggregate

The subdrains should be hydraulically connected to the free-draining granular base layer. Subdrains should be sloped to provide positive gravity drainage to reliable discharge points such as the stormwater detention basin. Periodic maintenance of subdrains is required for long-term proper performance.

Pavement Maintenance

The pavement sections represent minimum recommended thicknesses and, as such, periodic upkeep should be anticipated. Preventive maintenance should be planned and provided for through an on-going pavement management program. Maintenance activities are intended to slow the rate of pavement deterioration and to preserve the pavement investment. Pavement care consists of both localized (e.g., crack and joint sealing and patching) and global maintenance (e.g., surface sealing). Additional engineering consultation is recommended to determine the type and extent of a cost-effective program. Even with periodic maintenance, some movements and related cracking may still occur, and repairs may be required.

Pavement performance is affected by its surroundings. In addition to providing preventive maintenance, the civil engineer should consider the following recommendations in the design and layout of pavements:

■ Final grade adjacent to paved areas should slope down from the edges at a minimum 2%.

■ Subgrade and pavement surfaces should have a minimum 2% slope to promote proper surface drainage.

■ Install pavement drainage systems surrounding areas anticipated for frequent wetting.

■ Install joint sealant and seal cracks immediately.

Facilities | Environmental | Geotechnical | Materials 17

■ Seal all landscaped areas in or adjacent to pavements to reduce moisture migration to subgrade soils.

■ Place compacted, low permeability backfill against the exterior side of curb and gutter.

■ Place curb, gutter and/or sidewalk directly on clay subgrade soils rather than on unbound granular base course materials.

General Comments

Our analysis and opinions are based upon our understanding of the project, the geotechnical conditions in the area, and the data obtained from our site exploration.

Variations will occur between exploration point locations 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. Terracon should be retained as the

Geotechnical Engineer, where noted in this report, to provide observation and testing services during pertinent construction phases. If variations appear, we can provide further evaluation and supplemental recommendations. If variations are noted in the absence of our observation and testing services on-site, we should be immediately notified so that we can provide evaluation and supplemental recommendations.

Our Scope of Services does not include either specifically or by implication any environmental or biological (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.

Our services and any correspondence are intended for the sole benefit and exclusive use of our client for specific application to the project discussed and are accomplished in accordance with generally accepted geotechnical engineering practices with no third-party beneficiaries intended. Any third-party access to services or correspondence is solely for information purposes to support the services provided by Terracon to our client. Reliance upon the services and any work product is limited to our client and is not intended for third parties. Any use or reliance of the provided information by third parties is done solely at their own risk. No warranties, either express or implied, are intended or made.

Site characteristics as provided are for design purposes and not to estimate excavation cost. Any use of our report in that regard is done at the sole risk of the excavating cost estimator as there may be variations on the site that are not apparent in the data that could significantly effect excavation cost. Any parties charged with estimating excavation costs should seek their own site characterization for specific purposes to obtain the specific level of detail necessary for costing. Site safety and cost estimating including excavation support and dewatering requirements/design are the responsibility of others.

Facilities | Environmental | Geotechnical | Materials 18

Construction and site development have the potential to affect adjacent properties. Such impacts can include damages due to vibration, modification of groundwater/surface water flow during construction, foundation movement due to undermining or subsidence from excavation, as well as noise or air quality concerns. Evaluation of these items on nearby properties are commonly associated with contractor means and methods and are not addressed in this report. The owner and contractor should consider a preconstruction/precondition survey of surrounding development. If changes in the nature, design, or location of the project are planned, our conclusions and recommendations shall not be considered valid unless we review the changes and either verify or modify our conclusions in writing.

Figures

Contents:

GeoModel

6,000

6,010

6,020

6,030

6,040

6,050

6,060

6,070

6,080

E le va ti o n

M

S L

(f ee t)

Layering shown on this figure has been developed by the geotechnical engineer for purposes of modeling the subsurface conditions as required for the subsequent geotechnical engineering for this project.

Numbers adjacent to soil column indicate depth below ground surface.

NOTES:

B-01

B-02

B-03 B-04

B-05

B-06

B-07 B-08 B-09

B-10

B-11

B-12

B-13

B-14

B-15

B-16

This is not a cross section. This is intended to display the Geotechnical Model only. See individual logs for more detailed conditions.

1505 Old Happy Jack Rd

Storey Boulevard Extension

Storey Boulevard | Cheyenne, Wyoming

Cheyenne, WY

Terracon Project No. 24235022

GeoModel

Silty clayey sand, fine to coarse grained sand, with gravel and/or cobbles, brown to dark brown and tan to orange brown, very loose to medium dense

Clayey sand, fine to coarse grained, trace of fine to coarse gravel, tan to orange brown, loose to very dense4

Sandy lean clay, fine grained sand, tan to brown, stiff to hard, calcareous lenses5

LEGEND

Fill

Silty Clayey Sand

Clayey Sand

Sandy Lean Clay

Vegetative Soil

Silty Clayey Sand with Gravel

Model Layer General DescriptionLayer Name

About 6 inches thick1

Silty Sand, silty clayey sand, and/or poorly graded sand with silt and gravel, fine to coarse grained sand with gravel, brown to reddish brown

Silty Clayey Sand

Clayey Sand

Sandy Lean Clay

Vegetative Soil

Fill

15.5

5.5

15.5

1.5

14.5

15.5

15.5

0.5

0.5

0.5

15.5

0.5

15.5

0.5

15.5

0.5

15.5

15.5

4 2

15.5

15.5

15.5

Attachments

Exploration and Testing Procedures

Field Exploration

Number of Borings Approximate Boring

Depth (feet) Location

16 15 Along Storey Boulevard

Extension Alignment

Boring Layout and Elevations: Terracon personnel provided the boring layout using handheld GPS equipment (estimated horizontal accuracy of about ±10 feet) and referencing existing site features. Approximate ground surface elevations were provided by AVI.

Subsurface Exploration Procedures: We advanced the borings with a truck-mounted drill rig using continuous-flight augers (solid-stem and/or hollow-stem). Four samples were obtained in the upper 10 feet of each boring and at intervals of 5 feet thereafter.

In the split-barrel sampling procedure, a standard 2-inch outer diameter split-barrel sampling spoon was driven into the ground by a 140-pound automatic hammer falling a distance of 30 inches. The number of blows required to advance the sampling spoon the last 12 inches of a normal 18-inch penetration is recorded as the Standard Penetration

Test (SPT) resistance value. The SPT resistance values, also referred to as N-values, are indicated on the boring logs at the test depths. For modified California barrel sampling procedures, a 2½-inch outer diameter ring-lined sampler is used for sampling. Modified

California barrel sampling procedures are similar to standard split-barrel sampling procedures; however, blow counts are typically recorded for 6-inch intervals for a total of 12 inches of penetration. Bulk samples were collected from borings B-01, B-02, B-04, B-07, B-10, B-12, B-13, B-15, and B-16 at various depths. Additionally, a bulk sample was collected from the stockpile located at the project site (sample ID SP). For safety purposes, all borings were backfilled with auger cuttings after their completion.

We also observed the boreholes while drilling and at the completion of drilling for the presence of groundwater. Groundwater was not observed at these times in the boreholes.

The sampling depths, penetration distances, and other sampling information was recorded on the field boring logs. The samples were placed in appropriate containers and taken to our soil laboratory for testing and classification by a Geotechnical Engineer. Our exploration team prepared field boring logs as part of the drilling operations. These field logs included visual classifications of the materials observed during drilling and our interpretation of the subsurface conditions between samples. Final boring logs were prepared from the field logs. The final boring logs represent the Geotechnical Engineer's or Project Geologist’s interpretation of the field logs and include modifications based on observations and tests of the samples in our laboratory.

Laboratory Testing

The project engineer reviewed the field data and assigned laboratory tests. The laboratory testing program included the following types of tests:

■ Water content

■ Unit dry weight

■ Atterberg limits

■ Grain size analysis

■ Swell/consolidation

■ R-Value

■ Chemical analyses – pH, sulfates, chloride ion, sulfides, RedOx potential, total salts, and electrical resistivity

The laboratory testing program often included examination of soil samples by an engineer/geologist. Based on the results of our field and laboratory programs, we described and classified the soil samples in accordance with the Unified Soil

Classification System (USCS).

Site Location and Exploration Plans

Site Location Plan

Exploration Plan

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Site Location

DIAGRAM IS FOR GENERAL LOCATION ONLY, AND IS NOT INTENDED FOR CONSTRUCTION PURPOSES MAP PROVIDED BY MICROSOFT BING MAPS

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Exploration Plan

DIAGRAM IS FOR GENERAL LOCATION ONLY, AND IS NOT INTENDED FOR CONSTRUCTION PURPOSES MAP PROVIDED BY MICROSOFT BING MAPS

Exploration and Laboratory Results

Boring Logs (B-01 through B-16)

Atterberg Limits

Grain Size Distribution (2 pages)

Consolidation/Swell

R-Value (2 pages)

Corrosivity

Moisture-Density Relationship

FILL - SILTY SAND (SM), with gravel, fine to coarse grained, brown to reddish brown

SILTY CLAYEY…