250042- Geotech Investigation Report FINAL.docx.pdf

Final Geotechnical and Pavement Design Report

Proposed MCDOT – Tonto Hills Low Volume Roads

Tonto Hills Community, North of Cave Creek Road and Deer Trail Road

Maricopa County, Arizona

Contract No. CY 2020-022; MCDOT Project No. TT0609

Terracon Project No. 65205289 – Revision 1

March 19, 2021

Prepared for:

Maricopa County Department of Transportation

2901 West Durango Street

Phoenix, Arizona

Prepared by:

Terracon Consultants, Inc.

Tempe, Arizona

480.897.8200

3/19/2021

Terracon Consultants, Inc. 4685 South Ash Avenue, Suite H-4, Tempe, Arizona 85282

P [480] 897-8200 F [480]-897-1133 terracon.com

Terracon Consultants, Inc. 4685 South Ash Avenue, Suite H-4, Tempe, Arizona 85282

P [480] 897-8200 F [480]-897-1133 terracon.com

Maricopa County Department of Transportation

2901 West Durango Street

Phoenix, Arizona 85009

Attn: Mr. Gant Yasanayake Phone: (602) 506-4634 Email: gantyasanayake@mail.maricopa.gov

Re: Final Geotechnical and Pavement Design Report

Proposed MCDOT – Tonto Hills Low Volume Roads

Tonto Hills Community, North of Cave Creek Road and Deer Trail Road

Maricopa County, Arizona

Contract No. CY 2020-022, MCDOT Job No. TT0609

Dear Mr. Yasanayake:

Terracon Consultants, Inc. (Terracon) has completed the geotechnical and pavement engineering services for the above referenced project. These services were performed in general accordance with our Proposal No. P65205289, dated December 14, 2020. This geotechnical and pavement engineering report presents the results of the subsurface exploration and provides geotechnical and pavement engineering recommendations concerning the design of pavements for the 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 Consultants, Inc.

Matthew R. Kleinholz, E.I.T. Donald R. Clark, P.E.

Senior Staff Engineer Sr. Consultant/Sr. Principal

Copies to: Addressee (1 via email)

3/19/2021

Final Geotechnical and Pavement Design Report Proposed MCDOT – Tonto Hills Low Volume Roads ■ Maricopa County, Arizona

MCDOT Project No. TT0609 ■ March 19, 2021 ■ Terracon Project No. 65205289 – Revision 1

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TABLE OF CONTENTS

Page

1.0 INTRODUCTION

2.0 PROJECT INFORMATION

2.1 Project Description

2.2 Site Description

3.0 SUBSURFACE CONDITIONS

3.1 Site Geology

3.2 Subsurface Soil Conditions

3.3 Laboratory Test Data

3.4 Groundwater Conditions

3.5 Expansion Potential

3.6 Corrosion Considerations

4.0 PAVEMENT STRUCTURAL SECTION DESIGN

5.0 RETAINING WALL DESIGN AND CONSTRUCTION

5.1 General

5.2 Shallow Foundation Design Recommendations

5.3 Lateral Earth Pressure Parameters

6.0 MATERIALS DESIGN

6.1 Materials Specifications

6.2 Site Preparation and Earthwork

6.3 Excavation Characteristics

6.4 Permanent Slope Recommendations

6.5 Earthwork Factors

6.6 Grading and Drainage

7.0 GENERAL COMMENTS

Appendix A – Field Exploration Exhibit No.

Site Vicinity Map and Site Location ............................................................................... A-1

Exploration Plan .......................................................................................................... A-2

Field Exploration Description ....................................................................................... A-3

General Notes ............................................................................................................. A-4

Unified Soil Classification System ................................................................................ A-5

Boring Logs ............................................................................................ A-6 through A-42

Appendix B – Laboratory Testing

Laboratory Test Description ......................................................................................... B-1

Atterberg Limits Results ................................................................................. B-2 and B-3

Grain Size Distribution ............................................................................ B-4 through B-11

Standard Proctor Test Results .............................................................. B-12 through B-14

Consolidation Test Results ................................................................... B-15 through B-23

Direct Shear Test Results ..................................................................... B-24 through B-35

Summary of Laboratory Results ........................................................... B-36 through B-39

Motzz Laboratory Test Results ............................................................. B-40 through B-42

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List of Abbreviations

AASHTO ............... American Association of State Highway and Transportation

ABC ............................................................................ Aggregate Base Course

AC .......................................................................................... Asphalt Concrete

ACI ......................................................................... American Concrete Institute

ADOT ..................................................... Arizona Department of Transportation

ADWR ................................................ Arizona Department of Water Resources

ASTM ............................................. American Society for Testing and Materials

AR ............................................................................................. Asphalt Rubber

AZGS .......................................................................Arizona Geological Survey

CMP ................................................................. Corrugated Metal Pipe (culvert)

CTS................................................................................... Cement Treated Soil

DDF .................................................................... Directional Distribution Factor

ESALs ....................................................... Equivalent 18-kip Single Axle Loads

GI ................................................................................... AASHTO Group Index

GMSSC ....................................... Geogrid Mechanically Stabilized Soil Cement

LSS ........................................................................... Lime Stabilized Subgrade

MAG .................................................. Maricopa Association of Governments

MCDOT ................................... Maricopa County Department of Transportation

MSL or AMSL ................................. Mean Sea Level or Above Mean Sea Level

OGF ................................................................................ Overall Growth Factor

OSHA ....................................... Occupational Safety and Health Administration

PI ............................................................................................... Plasticity Index pcf ................................................................................... Pounds per cubic foot ppm .......................................................................................... Parts per million psf ................................................................................ Pounds per square foot psi ................................................................................ Pounds per square inch

RFS...................................................................................... Request for Scope

SPT .......................................................................... Standard Penetration Test

SN ........................................................................................ Structural Number

TEF .......................................................................... Traffic Equivalency Factor

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FINAL GEOTECHNICAL AND PAVEMENT DESIGN REPORT

PROPOSED MCDOT – TONTO HILLS LOW VOLUME ROADS

TONTO HILLS COMMUNITY, NORTH OF CAVE CREEK ROAD AND DEER TRAIL ROAD

MARICOPA COUNTY, ARIZONA

MCDOT PROJECT NO. TT0609

1.0 INTRODUCTION

This revised report presents the results of our geotechnical and pavement engineering services performed for proposed roadway improvements in the Tonto Hills Community, North of Cave Creek

Road and Deer Trail Road in Maricopa County, Arizona. The purpose of our engineering services is to provide information and geotechnical and pavement engineering recommendations relative to the following:

◼ subsurface soil conditions ◼ groundwater conditions

◼ retaining wall foundation parameters ◼ lateral earth pressures

◼ pavement design and construction ◼ pavement materials specifications

◼ earthwork

Our geotechnical engineering scope of work for the subsurface exploration for this project included

30 borings (designated as C-1 through C-19, R-1 through R-8, and S-1 through S-3). In addition, our geotechnical engineering services included laboratory testing, geotechnical engineering analysis, pavement engineering analyses, and preparation of this report.

Appendix A includes the following: Site Location (Exhibit A-1), Exploration Plan (Exhibit A-2), logs of the borings (Exhibits A-6 through A-42). The results of the laboratory testing performed on selected and representative soil samples obtained from the site during the field explorations are included in

Appendix B of this report. Descriptions of the field explorations and laboratory testing are included in their respective appendices.

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2.0 PROJECT INFORMATION

2.1 Project Description

Item Description

Project

Description

Based on the information provided, we understand the purpose of the project is to improve the existing graded roadways within the Tonto Hills Community. The roadways are planned to be paved with asphalt concrete. We understand some grading operations are planned and include cuts in order to improve drainage and erosion control of existing ephemeral washes that cross the roadways.

Proposed

Structures

We understand that cut areas are planned at various locations across the site, and some retaining walls may be constructed in cut areas of the site as part of the proposed improvements.

Grading

The proposed finished grades at the site are anticipated to remain about the same that currently exist. We understand some areas of the site may require cuts of 10 feet or less.

Pavements We understand the existing roadways will be classified as Very Low-Volume

(Residential) Roads.

2.2 Site Description

Item Description

Location

The proposed project is located in the Tonto Hills Community, North of Cave Creek

Road and Deer Trail Road in Maricopa County, Arizona. See the attached Site

Location (Exhibit A-1) and Exploration Plan (Exhibit A-2) in Appendix A for additional site location information.

Existing

Improvements

Based on the information provided and site reconnaissance made during our field exploration, the roadways within the community generally consist of graded roads with one lane in each direction.

Current Ground

Cover

Based on the information and site reconnaissance made during our field exploration, the existing ground cover at the site consists of paved and unpaved graded roadways. The roadways are generally bounded by native desert areas and residences.

Existing

Topography

The existing topography is highly variable, but overall appears to trend down to the northeast.

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3.0 SUBSURFACE CONDITIONS

3.1 Site Geology

The project area is located in the Basin and Range physiographic province (1Cooley, 1967) of the

North American Cordillera (2Stern, et al, 1979) of the southwestern United States. The southern portion of the Basin and Range province is situated along the southwestern flank of the Colorado

Plateau and is bounded by the Sierra Nevada Mountains to the west. Formed during middle and late Tertiary time (100 to 15 million years ago), the Basin and Range province is dominated by fault-controlled topography. These mountain ranges and valleys have evolved from generally complex movements and associated erosional and depositional processes.

Surficial geologic conditions mapped at the site (3Richard, et al, 2000) consist of middle

Proterozoic granitic rocks. This unit consists of mostly porphyritic biotite granite with large microcline phenocrysts, with local fine-grained border phases and aplite. Associated pegmatite and quartz veins are rare. This unit forms large plutons, including the Oracle Granite, Ruin

Granite, granite in the Pinnacle Peak - Carefree area northeast of Phoenix, and several bodies west of Prescott.

3.2 Subsurface Soil Conditions

Specific conditions encountered at each boring are indicated on the individual boring logs included in Appendix A (Exhibits A-6 through A-42) of this report of this report. Stratification boundaries on the boring logs represent the approximate location of changes in soil types; in-situ, the transition between materials may be gradual.

The field exploration of the site was performed between February 4 to 8, 2021. The approximate boring locations are shown on the Exploration Plan (Exhibit A-2) and consisted of the following test boring program as prescribed by MCDOT:

Number of Borings Boring Designation Boring Depth (feet) Location

19 C-1 through C-19 5 to 12½ Proposed Cut Areas

8 R-1 through R-8 4½ to 5½ Proposed Pavement

Areas

3 S-1 through S-3 1 Existing Washes

1 Cooley, M.E., 1967, Arizona Highway Geologic Map, Arizona Geological Society.

2 Stern, C.W., et al, 1979, Geological Evolution of North America, John Wiley & Sons, Santa Barbara, California.

3 Richard, S. M., Reynolds, S.J., Spencer, J. E., and Pearthree, P. A., 2000, Geologic Map of Arizona: Arizona Geological Survey

Map 35, 1 sheet, scale 1:1,000,000.

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Based on conditions encountered in the borings, subsurface conditions on the project site can be generalized as follows:

Description Approximate Depth to

Bottom of Stratum (feet) Material Description

Relative

Density

Surface ±0.25 to 4 inches thick Existing Asphalt Chip Seal and ABC ---

Stratum 1 15 (maximum depth explored)

Clayey Sand, Silty Clayey Sand, Silty Sand, Poorly Graded Sand, Well Graded Sand; all with variable amounts of silt, clay, and gravel

Variable

Loose to

Very Dense

3.3 Laboratory Test Data

Laboratory tests were performed on selected soil samples and the test results are presented in

Appendix B. Soil samples obtained from the borings were used for geotechnical and pavement engineering analysis for the proposed project. The following is a summary of laboratory testing performed on selected soils samples obtained from the borings:

Summary of Laboratory Testing

Laboratory Test Description of Test Results

Atterberg

Limits/Gradation

The Atterberg limits test results of the near surface soils along the project alignment generally exhibit non-plastic to medium plasticity characteristics (with plasticity indices ranging from 0 to 23, with an average of 9). The gradation test results of these near surface soils indicate percent fines (percent passing the sieve No. 200) ranging from approximately 3 to 23 percent (with an average of 12), percent sand ranged from approximately 50 to 83 percent, and percent gravel ranged from about 5 to 44 percent.

Moisture Content/Dry

Density

Testing of ring samples obtained from the borings indicated in-situ moisture contents ranging from approximately 1 to 13 percent with an average of approximately 4 percent; and in-situ dry densities ranging from approximately 78 to 133 pounds per cubic foot (pcf) with an average of approximately 116 pcf.

Consolidation

Results of consolidation testing indicate the granular soils typically exhibit low compressibility when tested at in-situ moisture content and density. In response to wetting the soils exhibited nil to significant hydro-collapse potential; however, potions of the hydro-collapse may be related in part to sample disturbance.

Laboratory Moisture-

Density Relationships

Standard Proctor (ASTM D698) test results indicated maximum dry densities of the site soils ranging from approximately 121.1 to 128.1 pounds per cubic foot (pcf) at optimum moisture contents ranging from approximately 7.3 to 9.9 percent.

Expansion Potential

Results of expansion potential testing indicates the soils across the site exhibit low to medium expansion potential (with expansion potentials ranging from 0.9 to 2.5 percent) of soil samples compacted to 95% percent of the maximum dry density at about 2 percent below the optimum moisture content.

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Summary of Laboratory Testing

Laboratory Test Description of Test Results

Direct Shear

Direct Shear (ASTM D3080) test results indicated friction angles of the site soils ranging from approximately 35 to 53 degrees and cohesions ranging from approximately 0 to 353 pounds per square foot (psf).

The following table indicates the roadway subgrade soils classification based on the American

Association of State Highway and Transportation Officials (AASHTO) soil classification system.

Based on these classifications, the pavement subgrade materials underlying the proposed new roadways are generally considered to have Excellent to Good support characteristics for pavements.

SUBGRADE SOIL CLASSIFCATION

Boring

No.

Approx.

Depth

USCS

Classification

AASHTO

Classification

AASHTO

Group Index

R-1 0 – 4 SP-SC A-2-4 0

R-2 0 – 4 SW-SC A-2-4 0

R-3 0 – 4 SM A-1-b 0

R-4 0 – 4 SC A-2-4 0

R-5 0 – 4 SW-SC A-2-4 0

R-6 0 – 4 SC A-2-6 0

R-7 0 – 4 SC A-2-6 0

R-8 0 – 4 SC A-2-6 0

Note: The AASHTO Classifications indicate the following general subgrade support characteristics:

Indicates Excellent to Good Subgrade Support Characteristics

Indicates Fair Subgrade Support Characteristics

Indicates Fair to Poor Subgrade Support Characteristics

The AASHTO classification method provides for the calculation of a Group Index, which is used as a scale for rating soil quality within a group. The Group Index (GI) values from the laboratory testing are summarized in the table above. Based on the Group Index values, the subgrade soils are considered uniform throughout the site.

3.4 Groundwater Conditions

Groundwater was not observed in any of the test borings at the time of our field exploration, nor when checked upon completion of drilling. These observations represent groundwater conditions at the time of the field exploration and may not be indicative of other times, or at other locations.

Groundwater conditions can change with varying seasonal and weather conditions, and other factors. Based on information obtained from the Arizona Department of Water Resources –

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Groundwater Data website (https://gisweb.azwater.gov/waterresourcedata/GWSI.aspx), the depth to regional groundwater in the vicinity of the site is presented in the following table:

Well Reg. I.D.

Depth to

Groundwater

(ft)

Water

Elevation

(ft MSL)

Date Last

Checked Comment

Local ID: A-06-05 10DDA1 60 3,425 12/5/2018

Near the intersection of Cave

Creek Road and Blue Wash

Road

Local ID: A-06-05 10CAB 251 3325 1/15/2003

Approx. 300 feet northeast of

Blue Wash Road and Old

Mine Road intersection

Local ID: A-06-05 15AA

UNSERV

40 3,284 1/3/1985

Approx. 0.3 miles south of the intersection of Blue Wash

Road and La Palma Road

3.5 Expansion Potential

The near surface soils encountered at the site along the proposed roadway improvements are comprised of primarily of silty sand, clayey sand, poorly graded sand, and well graded sand with variable amounts of silt, clay, and gravel. The plasticity characteristics of these site soils ranged from non-plastic to medium plasticity. Our laboratory testing also included performing standard laboratory moisture-density relationships (i.e. standard Proctor ASTM D698) and remolded swell tests on the near surface soils sampled from our borings.

The remolded swell testing on the soils indicated expansion potentials ranging from approximately

0.9 to 2.5 percent (with an average of 1.6 percent) on samples compacted to approximately 95 percent of their maximum dry density (ASTM D698) at a moisture content of approximately 2 percent below optimum with 144 pounds per square foot (psf) surcharge. Based on section

10.2.5.2 of the 2020 MCDOT Roadway Design Guide, subgrades with an expansion potential of

2.0 percent or greater are considered expansive and would require stabilization. We understand that the pavement design for this project is based on the 2015 MCDOT Very Low Volume Road

Design Guidelines which contains no requirements for expansive subgrades. However, the guideline recommends the MCDOT Materials Section be consulted for any recommendations for subgrade treatment.

3.6 Corrosion Considerations

Laboratory testing was performed on select samples obtained from the field exploration to determine corrosion potential for the project. The results of the laboratory testing are summarized in the following table:

https://gisweb.azwater.gov/waterresourcedata/GWSI.aspx

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Summary of Chemical Laboratory Testing

Boring Depth

(feet) pH

Minimum

Resistivity

(ohm-cm)

Sulfates

(ppm)

Chlorides

(ppm)

C-2 0 – 3 7.3 5,895 27 13

C-6 0 – 2 7.0 5,194 67 <3

C-7 0 – 5 7.3 3,090 33 6

C-9 0 – 2 6.8 6,660 120 <3

C-18 0 – 4 7.7 3,951 49 <3

R-4 0 – 4 7.1 2,389 36 57

R-5 0 – 4 6.6 1,560 13 52

R-8 0 – 4 6.7 1,879 29 9

S-1 0 – 1 8.1 7,314 19 <3

S-3 0 – 1 7.3 5,895 56 <3

Based on the American Concrete Institute (ACI) Design Manual, Section 318, Chapter 19 (ACI

318), concentrations of sulfates of less than 0.1 percent are considered to result in a low sulfate exposure. The concentration of sulfate indicated by the laboratory testing is anticipated to result in a low sulfate exposure to concrete placed at the site. Therefore, American Society for Testing and Materials (ASTM) Type I/II portland cement is considered suitable for concrete at the site in contact with similar soluble sulfate concentrations. In addition, the laboratory test results indicate the site soils have a chloride content below the chloride limits outlined in Chapter 19 of the ACI

318 for new concrete construction. The minimum resistivity testing indicates the site soils are considered mildly corrosive to corrosive toward ferrous metals, especially when soils have high moisture contents. The laboratory test results indicate the pH of the site soils is in the typical range for soils in the Phoenix metropolitan area.

These laboratory test values should be used to help determine potential corrosive characteristics of the on-site soils with respect to contact with the various underground materials which will be used for project construction. Refer to Summary of Laboratory Results contained in Appendix B for the complete results of the corrosivity testing performed on the site soils in conjunction with this geotechnical exploration. The corrosion information presented is specific to the samples tested. If the actual soils that will be in contact with the structures at the site are different than those tested, then additional corrosion testing should be performed. Terracon is not a corrosion engineer, and our scope of work was limited to performing corrosion laboratory tests on selected samples, presenting these results, and providing a brief comparison of the results to selected criteria. A qualified corrosion engineer should be consulted if corrosion of underground utilities and structures is a concern.

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4.0 PAVEMENT STRUCTURAL SECTION DESIGN

Based on information provided by MCDOT, the pavement thickness for the planned roadways improvements will be based on the MCDOT Very Low-Volume Road Design Guidelines. Section

4.5 (Pavement Structure) of these guidelines recommends two inches (2”) of asphalt concrete

(½” Gyratory Asphalt Mix for low traffic) over four inches (4”) of aggregate base over compacted subgrade (or as recommended by the MCDOT Materials Section). Asphalt roadway pavements are to have a continuous thickened edge (MAG Detail 201, Type B).

Based on the results of the laboratory testing, subgrade soils that will support the low volume pavements on the project have AASHTO classifications ranging from A-1-b to A-2-6, all of which have excellent to good subgrade support characteristics. Additionally, the AASHTO Group indices all are 0 which indicates fairly uniform conditions across the site. Based on the subgrade classifications and the uniformity of the subgrade soils, it does not appear that any mitigative efforts will be required to remove and replace poor subgrade soils to support the planned pavements.

As previously outlined, the remolded swell testing on the soils indicated expansion potentials ranging from approximately 0.9 to 2.5 percent (with an average of 1.6 percent). these test results represent only a limited amount of the subgrade soils with higher plasticity. The majority of the subgrade soils are of low plasticity or are non-plastic and are not considered expansive. The

2015 MCDOT Very Low Volume Road Design Guidelines recommends the MCDOT Materials

Section be consulted for any recommendations for subgrade treatment concerning expansive soils.

5.0 RETAINING WALL DESIGN AND CONSTRUCTION

5.1 General

We understand retaining wall structures are proposed for various locations across the project site.

Conventional cast-in-place concrete retaining walls supported on spread footing foundations are anticipated. Based on the geotechnical exploration, the existing soils near the bottom of proposed retaining wall structures generally consist of variable loose to very dense native soils with variable low to significant hydro-compaction (collapse) potential. Based on the results of our geotechnical engineering evaluation, it is our opinion that the proposed retaining wall structures should be supported on spread footing foundation systems founded on engineered fill materials.

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5.2 Shallow Foundation Design Recommendations

Design recommendations for retaining wall foundations for the proposed project are presented below.

DESIGN ITEM DESCRIPTION/RECOMMENDATION

Foundation Type Conventional Spread Footings

Bearing Material A minimum thickness of 24 inches of engineered fill material

Allowable Bearing Pressure 2,750 psf for shallow spread-type foundations

Minimum Embedment Depth 18 inches

Minimum Footing Dimension 18 inches

Total Estimated Settlement 1 inch or less

Estimated Differential Settlement ¾ total estimated settlement

Finished grade is defined as the lowest adjacent grade within 5 feet of the foundation. The allowable foundation bearing pressure applies to dead loads plus design live load conditions. The weight of the foundation concrete below grade may be neglected in dead load computations.

Foundations should be reinforced as necessary to reduce the potential for distress caused by differential foundation movement. The use of joints at openings or other discontinuities in walls is recommended. Foundation excavations should be observed by the geotechnical engineer. If the soil conditions encountered differ significantly from those presented in this report, supplemental recommendations will be required.

5.3 Lateral Earth Pressure Parameters

Lateral earth pressures on retaining walls will be dependent on the materials used as backfill. We recommend using site granular soils excavated from cut areas as structural backfill for the planned retaining walls. Structure Backfill should be in accordance with Section 203 of the ADOT

Standard Specifications. The on-site soils can be used as Structure Backfill provided they are processed to meet the Structure Backfill specifications. Recommended lateral earth pressures are as follows:

Design Case

Equivalent Fluid Pressures3

Effective Stress

(Drained) Condition1

Active Case 35 psf/ft

Passive Case 440 psf/ft

At-Rest Case 55 psf/ft

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Design Case

Equivalent Fluid Pressures3

Effective Stress

(Drained) Condition1

Coefficient of Base2 Friction

0.55

1Note: The values are based on the use of ADOT Structure Backfill or equivalent.

2Note: The coefficient of base friction should be reduced to 0.45 when used in conjunction with passive pressure.

3Note: The earth pressures do not include a safety factor. Therefore, appropriate safety factors should be applied to the design.

The lateral earth pressures herein do not include any factor of safety, they assume a horizontal backfill, they do not include surcharge loading, and they are not applicable for submerged soils/hydrostatic loading. Additional recommendations may be necessary if such conditions are to be included in the design. Appropriate additional loading and load factors should be applied in the design, if applicable.

Fill against foundations and retaining walls should be compacted to densities specified in the

Materials Design section of this report. Compaction of each lift adjacent to walls should be accomplished with hand-operated tampers or other lightweight compactors.

To reduce the potential of hydrostatic loading on retaining walls, drainage systems should be incorporated into the design where applicable. Drain systems consisting of continuous porous backfill or geocomposite as outlined in ADOT Standard Drawing SD 7.01, Sheet 1 of 5 (or other applicable standard drawing) are recommended. Drain systems should be discharged to weep holes appropriately placed along the face of each wall.

6.0 MATERIALS DESIGN

6.1 Materials Specifications

The use of Maricopa Association of Governments (MAG) 2020 Uniform Standard Specifications and Details for Public Works Construction and MCDOT supplements are recommended for work on the project. Based on the recommendations outlined in this report, the specifications, at a minimum, should include those listed in the following table.

MAG

Specification

Specification Title Comments/Recommendations

201 Clearing and Grubbing --

205 Roadway Excavation --

Structure Excavation and

Backfill

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MAG

Specification

Specification Title Comments/Recommendations

210 Imported Borrow --

211 Fill Construction

All fills placed on the project should be compacted to a minimum of 95% of the maximum density determined in accordance with ASTM D698. Moisture conditioning the fill materials to within 2% of optimum moisture content is recommended.

301 Subgrade Preparation Minimum depth of subgrade preparation in new pavement areas should be increased from 6 inches to 12 inches.

Placement and Construction of

Aggregate Base Course For areas of the site that may need a leveling course.

Placement and

Construction of Asphalt Concrete Pavement

½-inch Gyratory Asphalt Mix for low traffic is recommended for the asphalt concrete on this project in accordance with Table 710-5.

Placement and

Construction of Asphalt- Rubber Asphalt Concrete

702 Base Materials Aggregate Base Course on the project should conform to the requirements of Section 702.2.

710 Asphalt Concrete ½-inch Gyratory Asphalt Mix for low traffic is recommended to the asphalt concrete on this project in accordance with Table 710-5.

Trench Excavation, Backfilling and Compaction

Upon request, Terracon is available to assist in the review and development of the final specifications for the project.

6.2 Site Preparation and Earthwork

We recommend that all other site preparation and earthwork on the project be undertaken under the applicable portions of MAG Specifications. Recommended changes to these specifications as outlined in the preceding table should be included in the specifications or special provisions for the project.

Subgrade preparation in new pavement areas should include scarification, moisture conditioning, and compaction, as outlined in the MAG specifications. In addition, due to the loose relative density of the surface and near surface soils along the project alignment, the subgrade preparation beneath new pavement areas should be increased from the recommended 6-inch minimum depth outlined in the MAG specifications to a minimum depth of 12 inches.

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6.3 Excavation Characteristics

It is anticipated that excavations within the upper 5 feet for the construction along the project roadway alignments and cut areas can be accomplished with conventional earthmoving equipment capable of handling soils with variable loose to very dense relative densities and significant gravel contents. The subgrade soils exposed during construction could become relatively unstable and slough/cave due to the granular characteristics of the site soils. The stability of the subgrade may also be affected by precipitation, repetitive construction traffic, vibrations, or other factors.

The individual contractor(s) is responsible for designing and constructing stable, temporary excavations as required to maintain stability of both the excavation sides and bottoms.

Excavations should be sloped or shored in the interest of safety following local and federal regulations, including current OSHA excavation and trench safety standards.

6.4 Permanent Slope Recommendations

The following recommendations are presented for construction of new permanent slopes for the project. Permanent unprotected cut slopes be constructed at a slope ratio no steeper than 2H:1V

(horizontal to vertical). For cut slopes protected with slope paving or some form of erosion control, slopes no steeper than 1.5H:1V are recommended.

Permanent unprotected fill slopes should be constructed at a slope ratio no steeper than 2.5H:1V

(horizontal to vertical). For fill slopes protected with slope paving or some form of erosion control, slopes no steeper than 2H:1V are recommended.

6.5 Earthwork Factors

The earthwork factors have been based on a comparison of the dry densities from ring samples to the density of bulk samples compacted to 95 percent of maximum dry density as determined by ASTM D698. Based on a comparison of the average in-situ dry densities to 95 percent of the average Standard Proctor maximum dry density, we recommend a shrinkage factor of about 5 to

7 percent be applied for earthwork on the project.

These estimates are general in nature, and are based on our experience, limited data from our field exploration, and the soil conditions encountered at the site. Earthwork factors may vary dependent upon the actual subsurface conditions, which may include variations in soil gradations and gravel contents. Earthwork values are also expected to be less in areas subjected to lower levels of compaction or where the existing natural soils are denser. Similarly, earthwork values are also expected to be greater in areas subjected to higher levels of compaction or where the existing natural soils are looser.

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A ground compaction factor of approximately 0.1 feet should be applied when estimating the change in elevation of the native soil surface due to scarification, moisture conditioning and re-compaction prior to fill placement.

6.6 Grading and Drainage

To the extent possible, grades should provide effective drainage away from the proposed pavement structures and retaining walls during and after construction. Water permitted to pond next to the pavements and walls can result in moisture content increases in subgrade soils and consequently in premature deterioration of the pavement structure, increased maintenance, and excessive settlement beyond those estimated in this report.

Positive drainage should be provided during construction and maintained throughout the life of the proposed improvements at the site. Infiltration of water into footing excavations and trenches should be prevented during construction. We recommend that protective slopes be provided with a minimum grade of approximately 5 percent for at least 10 feet from the pavement structures.

Backfill placed at the site should be well compacted and free of all construction debris to reduce the moisture infiltration.

7.0 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. Natural 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 or collaboration through this system 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

Resourceful ■ Reliable ■ Responsive 14 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.

Resourceful ■ Reliable ■ Responsive

APPENDIX A

FIELD EXPLORATION

SITE LOCATION

Proposed MCDOT – Tonto Hills Low Volume Roads

Tonto Hills Community

Maricopa County, Arizona

AERIAL PHOTOGRAPHY PROVIDED BY MICROSOFT BING MAPS

4685 S Ash Ave Ste H-4

Tempe, AZ 85282-6767

65205289 Project Manager:

Drawn by:

Checked by:

Approved by:

MRK

DRC

DCR

AS SHOWN

Exhibit A-1/2

3/12/21

Project No.

Scale:

File Name:

Date:

A-1

Exhibit

EF

SITE

EXPLORATION PLAN

Proposed MCDOT – Tonto Hills Low Volume Roads

Tonto Hills Community

Maricopa County, Arizona

4685 S Ash Ave Ste H-4

Tempe, AZ 85282-6767

DIAGRAM IS FOR GENERAL LOCATION ONLY, AND IS

NOT INTENDED FOR CONSTRUCTION PURPOSES

65205289

AERIAL PHOTOGRAPHY PROVIDED

BY MICROSOFT BING MAPS

MRK

DRC

DCR

AS SHOWN

Exhibit A-1/2

3/12/21

Scale:

A-2

Exhibit Project Manager:

Drawn by:

Checked by:

Approved by:

Project No.

File Name:

Date:

EF

Resourceful ■ Reliable ■ Responsive Exhibit A-3

Field Exploration Description

A total of 30 test borings drilled to depths of approximately 1 to 15 feet below the existing ground surface were completed between February 4 to 8, 2021. The approximate boring locations are shown on the attached Exploration Plan, Exhibit A-2.

Boring Layout and Elevations: MCDOT provided the proposed boring layout prior to the field exploration. Coordinates for each boring were obtained with a handheld GPS unit (estimated horizontal accuracy of about ±15 feet). If elevations and a more precise boring layout are desired, we recommend the borings be surveyed.

Subsurface Exploration Procedures: The cut area and roadway borings (Borings C-1 through

C-19 and R-1 through R-8) were advanced using a combination of 4-inch outside diameter (O.D.)

hand auger and a truck-mounted CME-75 drill rig utilizing 8-inch (O.D.) hollow-stem augers. At the locations of C-1, 6, 8, 9, 10, 13, and 15, the planned boring location could not be accessed by drill rig due to steep slopes. At these locations, the boring was advanced at the planned location with a 4-inch O.D. hand auger until refusal. If hand auger refusal occurred at an elevation above the adjacent roadway elevation, the remainder of the slope side was logged to adjacent roadway elevation. The hand auger and slope side portion of the boring was designated as “A” and a secondary boring was advanced using the drill rig at the roadway elevation and was designated as “B”. At selected intervals, samples of the subsurface materials were taken at each boring location by driving split-spoon (SPT) or ring-lined barrel samplers in general accordance with

ASTM Standards. In the split-barrel sampling procedure, a standard 2-inch outer diameter split-barrel sampling spoon is 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. A 3-inch O.D. and 2.5-inch I.D. ring lined sampler was used for sampling in the soil borings. Ring-lined, split-barrel sampling procedures are similar to standard split spoon sampling procedure; however, blow counts are typically recorded for 6-inch intervals for a total of 12 inches of penetration. Bulk samples of subsurface materials were obtained from all the borings. The sediment area borings (S-1 through S-3) were advanced with a 4-inch O.D.

hand auger to a depth of approximately 1 foot each. A bulk sample of the subsurface materials was obtained from each boring.

Groundwater was not encountered during drilling and sampling.

For safety purposes, the borings were backfilled with auger cuttings and the borings performed in the existing roadway were backfilled with auger cuttings mixed with fast setting cement. The borings performed on the pavement were patched with cold patch asphalt concrete after their completion.

Water levels indicated on the soil boring logs are the levels measured in the borehole at the times indicated.

Groundwater level variations will occur over time. In low permeability soils, accurate determination of groundwater levels is not possible with short term water level observations.

No Recovery

Modified Dames & Moore Ring Sampler

Grab Sample

Modified California

Ring Sampler

GENERAL NOTES

4 - 8

Unconfined Compressive Strength, Qu, psf

S T

R E

N G

T H

T E

R M

S

Over 12 in. (300 mm) 12 in. to 3 in. (300mm to 75mm) 3 in. to #4 sieve (75mm to 4.75 mm) #4 to #200 sieve (4.75mm to 0.075mm Passing #200 sieve (0.075mm)

Particle Size

RELATIVE DENSITY OF COARSE-GRAINED SOILS

< 5 5 - 12 > 12

Percent of Dry Weight

Descriptive Term(s) of other constituents

RELATIVE PROPORTIONS OF FINES

1 - 10 11 - 30

> 30

Plasticity Index

S A

M P

L

IN

G

LOCATION AND ELEVATION NOTES

> 99 4,000 to 8,000

2,000 to 4,000

Macro Core

1,000 to 2,000

500 to 1,000 less than 500

Stiff59 - 98

19 - 5810 - 29

Soft7 - 18

Very Soft0 - 60 - 3Very Loose

Hard

(More than 50% retained on No. 200 sieve.)

Density determined by Standard Penetration Resistance

Includes gravels, sands and silts.

Percent of Dry Weight

Major Component of Sample

Water Level After a Specified Period of Time

Water Initially Encountered

Descriptive Term(s) of other constituents

< 15 15 - 29 > 30

Term

PLASTICITY DESCRIPTION

8 - 15

Rock Core

Split SpoonShelby Tube

W A

T E

R L

E V

E L

30 - 50

5 - 9Medium-Stiff

3 - 42 - 44 - 9

< 30 - 1

Very Dense

Dense

Medium Dense

Ring Sampler Blows/Ft.

Ring Sampler Blows/Ft.

Standard Penetration or N-Value

Blows/Ft.

Very Stiff

Loose

Descriptive Term (Consistency)

Standard Penetration or N-Value

Blows/Ft.

Trace With Modifier

RELATIVE PROPORTIONS OF SAND AND GRAVEL GRAIN SIZE TERMINOLOGY

Water Level After a Specified Period of Time

Trace With Modifier

Bulk

Soil classification is based on the Unified Soil Classification System. Coarse Grained Soils have more than 50% of their dry weight retained on a #200 sieve; their principal descriptors are: boulders, cobbles, gravel or sand. Fine Grained Soils have less than 50% of their dry weight retained on a #200 sieve; they are principally described as clays if they are plastic, and silts if they are slightly plastic or non-plastic. Major constituents may be added as modifiers and minor constituents may be added according to the relative proportions based on grain size. In addition to gradation, coarse-grained soils are defined on the basis of their in-place relative density and fine-grained soils on the basis of their consistency.

Unless otherwise noted, Latitude and Longitude are approximately determined using a hand-held GPS device. The accuracy of such devices is variable. Surface elevation data annotated with +/- indicates that no actual topographical survey was conducted to confirm the surface elevation. Instead, the surface elevation was approximately determined from topographic maps of the area.

> 8,000

DESCRIPTIVE SOIL CLASSIFICATION

(50% or more passing the No. 200 sieve.)

Consistency determined by laboratory shear strength testing, field visual-manual procedures or standard penetration resistance

(HP)

(T)

(b/f)

N

(PID)

(OVA)

Hand Penetrometer

Torvane

Standard Penetration Test (blows per foot)

N value

Photo-Ionization Detector

Organic Vapor Analyzer

CONSISTENCY OF FINE-GRAINED SOILS

> 42> 30

19 - 4215 - 30> 50

10 - 18

Boulders Cobbles Gravel Sand Silt or Clay

Non-plastic Low Medium High

Descriptive Term (Density)

DESCRIPTION OF SYMBOLS AND ABBREVIATIONS

F

IE

L D

T E

S T

S

Exhibit A-4

UNIFIED SOIL CLASSIFICATION SYSTEM

Criteria for Assigning Group Symbols and Group Names Using Laboratory Tests A

Soil Classification

Group

Symbol Group Name

B

Coarse Grained Soils:

More than 50% retained on No. 200 sieve

Gravels:

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

Clean Gravels:

Less than 5% fines C

Cu 4 and 1 Cc 3 E

GW Well-graded gravel F

Cu 4 and/or 1 Cc 3

GP Poorly graded gravel

Gravels with Fines:

More than 12% fines C

Fines classify as ML or MH GM Silty gravel F,G,H

Fines classify as CL or CH GC Clayey gravel F,G,H

Sands:

50% or more of coarse fraction passes No. 4 sieve

Clean Sands:

Less than 5% fines D

Cu 6 and 1 Cc 3

SW Well-graded sand I

Cu 6 and/or 1 Cc 3

SP Poorly graded sand I

Sands with Fines:

More than 12% fines D

Fines classify as ML or MH SM Silty sand G,H,I

Fines classify as CL or CH SC Clayey sand G,H,I

Fine-Grained Soils:

50% or more passes the

No. 200 sieve

Silts and Clays:

Liquid limit less than 50

Inorganic:

PI 7 and plots on or above “A” line

J CL Lean clay

K,L,M

PI 4 or plots below “A” line J ML Silt

Organic:

Liquid limit - oven dried

0.75 OL

Organic clay

K,L,M,N

Liquid limit - not dried Organic silt K,L,M,O

Silts and Clays:

Liquid limit 50 or more

Inorganic:

PI plots on or above “A” line CH Fat clay

PI plots below “A” line MH Elastic Silt

Organic:

Liquid limit - oven dried

0.75 OH

Organic clay

K,L,M,P

Liquid limit - not dried Organic silt K,L,M,Q

Highly organic soils: Primarily organic matter, dark in color, and organic odor PT Peat

A Based on the material passing the 3-inch (75-mm) sieve

B If field sample contained cobbles or boulders, or both, add “with cobbles or boulders, or both” to group name.

C

Gravels with 5 to 12% fines require dual symbols: GW-GM well-graded gravel with silt, GW-GC well-graded gravel with clay, GP-GM poorly graded gravel with silt, GP-GC poorly graded gravel with clay.

D

Sands with 5 to 12% fines require dual symbols: SW-SM well-graded sand with silt, SW-SC well-graded sand with clay, SP-SM poorly graded sand with silt, SP-SC poorly graded sand with clay

E Cu = D60/D10 Cc =

DxD

)(D

If soil contains 15% sand, add “with sand” to group name.

G If fines classify as CL-ML, use dual symbol GC-GM, or SC-SM.

H If fines are organic, add “with organic fines” to group name.

I If soil contains 15% gravel, add “with gravel” to group name.

J If Atterberg limits plot in shaded area, soil is a CL-ML, silty clay.

K If soil contains 15 to 29% plus No. 200, add “with sand” or “with gravel,” whichever is predominant.

L

If soil contains 30% plus No. 200 predominantly sand, add “sandy” to group name.

M

If soil contains 30% plus No. 200, predominantly gravel, add

“gravelly” to group name.

N

PI 4 and plots on or above “A” line.

O

PI 4 or plots below “A” line.

P

PI plots on or above “A” line.

Q

PI plots below “A” line.

Exhibit A-5

1228-19-9

POORLY GRADED SAND WITH CLAY AND GRAVEL (SP-SC), fine to coarse sand, fine to coarse gravel, low plasticity, brown, hand auger at planned location on top of slope approximately 5 feet above roadway elevation hand auger refusal at a depth of 3 feet, remainder of boring to pavement subgrade elevation logged from side of slope boring continued at roadway elevation with drill rig as Boring C-1B

Boring Terminated at 5 Feet 5.0

Stratification lines are approximate. In-situ, the transition may be gradual.

T H

IS

B

O R

IN

G

L O

G

IS

N O

T V

A

LI

D

IF

S E

P A

R A

T E

D F

R O

M O

R

IG

IN

A

L R

E P

O R

T

G E

O S

M A

R T

L O

G -N

O W

E

LL

P

R O

P O

S E

D M

C D

O T

.G P

J T

E R

R A

C O

N _D

A T

A T

E M

P

LA

T E

.G D

T

/1 2/

W A

T E

R L

E V

E L

O B

S E

R V

A T

IO

N

S

D E

P T

H

F t.)

F

IE

LD

T

E S

T R

E S

U

LT

S

Tonto Hills Subdivision Scottsdale, Arizona

SITE:

Advancement Method:

4" Hand Auger

Abandonment Method:

Boring backfilled with auger cuttings upon completion.

Notes:

Project No.: 65205289

Drill Rig: Hand Auger

Boring Started: 02-04-2021

BORING LOG NO. C-1A

Maricopa County DOTCLIENT:

Phoenix, Arizona

Driller: J&R

Boring Completed: 02-04-2021

PROJECT: Proposed MCDOT - Tonto Hills Low Volume Roads

4685 S Ash Ave, Ste H-4 Tempe, AZ

WATER LEVEL OBSERVATIONS

Groundwater not encountered

P E

R C

E N

T F

IN

E

S

W A

T E

R C

O N

T E

N T

D R

Y U

N

IT

W E

IG

H

T pc f)

ATTERBERG

LIMITS

LL-PL-PI

LOCATION

Latitude: 33.8770° Longitude: -111.8375°

G R

A P

H

IC

L O

G

DEPTH

S A

M P

LE

T

Y P

Exhibit A-6

3-4

6-6

21-34-22 N=56

50/4"

6.6

8.7

3.8

CLAYEY SAND WITH GRAVEL (SC), fine to coarse sand, fine to coarse gravel, low plasticity, brown, loose, continuation of Boring C-1A adjacent to slope

POORLY GRADED SAND WITH SILT AND GRAVEL (SP-SM), fine to coarse sand, fine to coarse gravel, low plasticity, brown, loose very dense

Boring Terminated at 9.5 Feet

3.0

9.5

Hammer Type: AutomaticStratification lines are approximate. In-situ, the transition may be gradual.

T H

IS

B

O R

IN

G

L O

G

IS

N O

T V

A

LI

D

IF

S E

P A

R A

T E

D F

R O

M O

R

IG

IN

A

L R

E P

O R

T

G E

O S

M A

R T

L O

G -N

O W

E

LL

P

R O

P O

S E

D M

C D

O T

B .G

P J

T E

R R

A C

O N

_D A

T A

T E

M P

LA

T

E .G

D T

/1

/2

W A

T E

R L

E V

E L

O B

S E

R V

A T

IO

N

S

D E

P T

H

F t.)

F

IE

LD

T

E S

T R

E S

U

LT

S

Tonto Hills Subdivision Scottsdale, Arizona

SITE:

Advancement Method:

8" Hollow-Stem Auger

Abandonment Method:

Boring backfilled with auger cuttings upon completion.

Notes:

Project No.: 65205289

Drill Rig: CME 75

Boring Started: 02-04-2021

BORING LOG NO. C-1B

Maricopa County DOTCLIENT:

Phoenix, Arizona

Driller…