geotechnical engineering pavement section thickness...

GEOTECHNICAL ENGINEERING PAVEMENT SECTION THICKNESS DESIGN

RECOMMENDATIONS

For The

Third Street Extension portion of the Montezuma-Cortez High School Project

Prepared For: Mr. Alex Carter, Superintendent

Montezuma County School District RE-1, and, Mr. Jim Ketter, PE, KPMC

Project Number: 53088GE July 15, 2013

PN: 53088GE

July 15, 2013

1

1.0 REPORT INTRODUCTION ................................................................................................ 2

1.1 Scope of Project ................................................................................................................... 3

2.0 GEOTECHNICAL ENGINEERING STUDY .................................................................... 3

2.1 Geotechnical Engineering Study Scope of Service .............................................................. 3

3.0 FIELD STUDY....................................................................................................................... 5

3.1 Project location.................................................................................................................... 5

3.2 Site Description and Geomorphology.................................................................................. 5

3.3 Subsurface Soil and Water Conditions ................................................................................ 5

4.0 LABORATORY STUDY ...................................................................................................... 7

5.0 ASPHALT PAVEMENT RECOMMENDATIONS ........................................................... 8

6.0 CONSTRUCTION MONITORING AND TESTING ...................................................... 11

7.0 CONCLUSIONS AND CONSIDERATIONS ................................................................... 11

FIELD TEST RESULTS………………………………………………………….…Appendix A

Logs of Test Borings

LABORATORY TEST RESULTS………………………………………………….Appendix B

Sieve Analysis and Atterberg Test Limits Results

Dry Density/Moisture Content (Proctor) Results

California Bearing Ration Test Results

PN: 53088GE

July 15, 2013

2

1.0 REPORT INTRODUCTION

This report presents our geotechnical engineering recommendations for the proposed

3rd Street Pavement Study Phase 2, Design Level Geotechnical Engineering Study for

the proposed Montezuma-Cortez High School in Cortez, Colorado. This report was requested by

Mr. Jim Ketter, PE, KPMC, Owners Representative, Project Manager. The field study was

completed on July 2, 2013. The laboratory study was completed on July 15, 2013.

The information provided in this report is used to help develop a design and subsequently

implement construction strategies that are appropriate for the subsurface soil and water

conditions encountered. It is important that the geotechnical engineer be consulted throughout

the design and construction process to verify the implementation of the geotechnical engineering

recommendations provided in this report. Generally the recommendations and technical aspects

of this report are intended for design and construction personnel who are familiar construction

concepts and techniques, and understand the terminology presented below. We should be

contacted if any questions or comments arise as a result of the information presented below.

The following outline provides a synopsis of the various portions of this report;

� Sections 1.0 and 2.0 provide an introduction and an establishment of our scope of

service.

� Sections 3.0 and 4.0 of this report present our geotechnical engineering field and

laboratory studies

� Sections 5.0 presents our geotechnical engineering design data and subsequent

recommendations which are based on our engineering analysis of the data obtained for

the project.

� Section 6.0 provides a brief discussion of construction sequencing and strategies which

may influence the geotechnical engineering characteristics of the site.

The discussion and construction recommendations presented in Section 6.0 are intended to

help develop site soil conditions that are consistent with the geotechnical engineering

recommendations presented previously in the report. The construction considerations section is

not intended to address all of the construction planning and needs for the project site, but is

intended to provide an overview to aid the owner, design team, and contractor in understanding

some construction concepts that may influence some of the geotechnical engineering aspects of

the site and proposed development.

The data used to generate our recommendations are presented throughout this report and in the

attached figures.

PN: 53088GE

July 15, 2013

3

1.1 Scope of Project

We understand that the proposed project will consist of designing and constructing and

extension of 3rd Street adjacent to the north of the proposed Montezuma-Cortez High School site.

We understand the portion of 3rd Street that will be constructed is located east of South Sligo

Street and will end at the east side of the proposed school development. We understand the

current grade within this section of the 3rd Street right-of-way is currently at the approximate

proposed top of subgrade elevation for the street construction. The new roadway extension will

consist of asphalt pavement supported by aggregate base course material.

2.0 GEOTECHNICAL ENGINEERING STUDY

This section of this report presents the results of our field and laboratory study and our

geotechnical engineering recommendations based on the data obtained.

Our services include a geotechnical engineering study of the subsurface soil and water

conditions of the project sites for the proposed roadway project.

2.1 Geotechnical Engineering Study Scope of Service

The scope of our study which was delineated in our proposal for services, and the order of

presentation of the information within this report, is outlined below.

Field Study

• We advanced five (5) test borings at select locations on the proposed alignment for the

extension of 3rd Street within the City of Cortez Limits.

• Select driven sleeve and bulk soil samples were obtained from the test borings and

returned to our laboratory for testing.

PN: 53088GE

July 15, 2013

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Laboratory Study

• The laboratory testing and analysis of the samples obtained for the project portion of the

roadway included;

� Moisture content of select samples obtained from the field study,

� One (1) Atterberg Limits test, and one (1) sieve analysis test for classification of

he sample tested,

� One (1) moisture content/dry density (Modified Proctor ASTM D1157) test on a

bulk sample of the subgrade soil materials, and,

� One (1) California Bearing Ratio (CBR) test performed on the subgrade soil

materials.

Geotechnical Engineering Recommendations

• This report addresses the geotechnical engineering aspects of the site and provides

recommendations including;

Geotechnical Engineering Section(s)

� Subsurface soil and water conditions that may influence the project design

and construction considerations

� Geotechnical engineering design data and recommendations that may be

used for the roadway design project.

Construction Consideration Section

� Compaction recommendations for the subgrade soils, aggregate base

course materials, and asphalt pavement materials proposed at the site.

• This report provides design parameters, but does not provide civil engineering design.

The project civil engineer may be contacted to provide a design based on the

information presented in this report.

• Our subsurface exploration, laboratory study and engineering analysis do not address

environmental or geologic hazard issues

PN: 53088GE

July 15, 2013

5

3.0 FIELD STUDY

3.1 Project location

The portion of the proposed road extension project that this report addresses, initiates at the east

side of South Sligo Street and ends at the east side of the proposed school development. The

project site is located in the City of Cortez Limits.

3.2 Site Description and Geomorphology

The proposed road extension will traverse a previously excavated and graded roadway

alignment, which we suspect was completed during the construction of Walmart, located

adjacent and to the north of the 3rd Street project. We observed aggregate road base material on

the ground surface along the 3rd Street road alignment from South Sligo Street east

approximately two hundred and fifty (250) feet. We understand the existing elevation is near

proposed subgrade elevation.

The subsurface soil and rock materials encountered in the vicinity of the project consist of a

variable depth, but generally shallow, sandy clay soil mantle overlying the Dakota Sandstone

Formation. The sandy clay soil materials encountered in the vicinity of the project typically

provide low to moderate strength characteristics for support of flexible asphalt pavement. The

formational material consists of inter-bedded layers of sandstone, shale, and claystone materials.

The sandstone materials encountered are often very hard and may require blasting or other

aggressive techniques for excavation.

3.3 Subsurface Soil and Water Conditions

We advanced five (5) shallow test borings in select areas of the proposed road alignment within

the City of Cortez Limits. The approximate location of the test borings are shown on the figure

below obtained from The City of Cortez. The subsurface conditions encountered in our test

borings are tabulated below.

PN: 53088GE

July 15, 2013

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The approximate test boring location shown above were prepared using Google Earth and notes

taken during the field work and is intended to show the approximate test boring locations for

reference purposes only.

In Test Boring One, we encountered ten (10) inches of a three-quarter inch minus aggregate

base course material, over a sandy clay soil material. In Test Borings Two through Five, we

encountered slightly moist and medium stiff sandy clay soil material to depths ranging from

about one (1) to one and two (2) feet where we encountered the weathered Dakota Sandstone.

The formational sandstone material encountered was medium hard to hard. The test borings

were advanced to a depth of four (4) feet below the ground surface elevation adjacent to our test

borings.

3RD

TB-1 3RD

TB-2 3RD

TB-3 3RD

TB-4 3RD

TB-5

PN: 53088GE

July 15, 2013

7

The logs of the subsurface soil conditions encountered in our test borings are presented in

Appendix A. The logs present our interpretation of the subsurface conditions encountered

exposed in the test borings at the time of our field work. Subsurface soil and water conditions

are often variable across relatively short distances. It is likely that variable subsurface soil and

water conditions will be encountered during construction. Laboratory soil classifications of

samples obtained may differ from field classifications.

4.0 LABORATORY STUDY

The laboratory study included tests to estimate the strength, swell and consolidation potential of

the soils tested. We performed the following tests on select samples obtained from the test

borings.

Atterberg Limits and Sieve Analysis; the plastic limit, liquid limit and plasticity index of some

of the soil samples was determined in accordance with ASTM D4318. In conjunction with the

Atterberg Limits tests, sieve analysis tests were performed in accordance with ASTM D422 and

D1140. The results of the sieve analysis and Atterberg Limits testing performed are provided in

Appendix B.

Moisture content-dry density relationship (Proctor) tests; We performed laboratory moisture

content-dry density tests to assess the relationship between the soil moisture content and dry

density. The Proctor tests were performed in accordance with ASTM D1557. We obtained a

maximum dry density ranging of 129.0 pounds per cubic foot at an optimum moisture content of

9.0 percent for the subgrade soil materials encountered in our test borings. The results of the

laboratory Proctor tests are presented in Appendix B.

California Bearing Ratio (CBR) Tests; We assessed the pavement section support

characteristics of select composite soil samples of the subgrade materials in general accordance

with ASTM D1883. We obtained a CBR value of about 6.5 assuming the subgrade soil materials

are compacted to at least ninety (90) percent of the maximum dry density as defined by the

Modified Proctor (ASTM D1557). The results of the CBR tests are presented in Appendix B.

PN: 53088GE

July 15, 2013

8

5.0 ASPHALT PAVEMENT RECOMMENDATIONS

We performed a California Bearing Ratio (CBR) test on a composite sample of soil obtained

from the project site. Based on the results of the CBR test we used an R-Value of 15 in our

analysis for the pavement section thickness design.

The existing aggregate base course material encountered in Test Boring One and observed along

the western 250 feet of the road alignment may be used to establish roadway subgrade elevations.

We do not believe that it will be feasible to adequately excavate remove and stockpile this

materials without significant contamination of the material with fine grained clay material.

However, if it is desirable to utilize the existing aggregate materials within the pavement sections

provided below, the material should be removed and stockpiled prior to reuse. We should be

contacted to observe and perform additional tests on the stockpiled material to provide additional

pavement section thickness recommendations. This material is suitable for incorporation into the

subgrade soils, and may be particularly useful for stabilizing any subgrade soil areas where soft

or yielding conditions are encountered.

We recommend that the subgrade soils be proof-rolled prior to the scarification and processing

operations. Any soft areas observed during the proof-rolling operations should be removed and

replaced with properly processed materials and/or granular aggregate materials as part of the

subgrade preparation.

The site subgrade pavement section support soils must be scarified to a depth of twelve (12)

inches, moisture conditioned and compacted prior to placement of the overlying aggregate

pavement section materials. The material should be moisture conditioned to within about two (2)

percent of the optimum moisture content and compacted to at least ninety (90) percent of

maximum dry density as determined by the modified Proctor test, ASTM D1557. In areas where

hard formational material is encountered, the scarification process is not necessary.

The surface of the subgrade soil should be graded and contoured to be approximately parallel to

the finished grade of the asphalt surface.

The aggregate materials used within the pavement section should conform to the requirements

outlined in the current Specifications for Road and Bridge Construction, Colorado Department of

Transportation (CDOT). The aggregate base material should be a three-quarter (3/4) inch minus

material that conforms to the CDOT Class 6 aggregate base course specifications and have an R-

value of at least 78. The aggregate sub-base course should conform to the CDOT specifications

for Class 2 material and should have a minimum R-value 70. Other material may be suitable for

PN: 53088GE

July 15, 2013

9

use in the pavement section, but materials different than those listed above should be tested and

observed by us prior to inclusion in the project design or construction. Aggregate sub-base and

base-course materials should be compacted to at least ninety-five (95) percent of maximum dry

density as defined by the modified Proctor test, ASTM D1557.

We recommend that the asphalt concrete used on this project be mixed in accordance with a

design prepared by a licensed professional engineer, or an asphalt concrete specialist. We should

be contacted to review the mix design prior to placement at the project site. We recommend that

the asphalt concrete be compacted to between ninety-two (92) and ninety-six (96) percent of the

maximum theoretical density.

We have provided several pavement section design thicknesses below. The structural support

characteristics of each section are approximately equal. The project civil engineer, or contractor

can evaluate the best combination of materials for economic considerations.

We have provided pavement section thicknesses for 100,000 to 500,000 - 18,000 pound

equivalent single axle loads (18k ESAL). We are available to provide additional design sections,

if these are desired. We recommend that a relatively detailed attempt be made to project the

potential type and frequency of traffic use for the roadway.

Pavement Section Design Thickness

100,000 18k ESAL

Pavement Section Component Alternative Thicknesses of Each Component

(inches)

Asphalt Concrete 3 3 3.5 3.5 4

Class 6 6 11 4 10 8

Class 2 7 0 8 0 0

Reconditioned Subgrade 12 12 12 12 12


150,000 18k ESAL


(inches)

Asphalt Concrete 3 3 3.5 3.5 4 4

Class 6 6 13 4 6 4 9

Class 2 9 0 9 6 6 0

Reconditioned Subgrade 12 12 12 12 12 12

PN: 53088GE

July 15, 2013

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250,000 18k ESAL


(inches)

Asphalt Concrete 3 3 3 3.5 3.5 4 4 4

Class 6 6 8 15 6 14 4 6 12

Class 2 12 10 0 10 0 11 8 0

Reconditioned Subgrade 12 12 12 12 12 12 12 12


500,000 18k ESAL


(inches)

Asphalt Concrete 4 4 4.5 4.5 4.5 5 5

Class 6 6 8 4 6 8 6 12

Class 2 13 10 13 11 8 8 0

Reconditioned Subgrade 12 12 12 12 12 12 12

The pavement section thicknesses tabulated above are appropriate for the post-construction

traffic use. Heavy construction equipment traffic will have a significant influence on the quality,

character, and design life of the pavement sections tabulated above. If possible we recommend

that a partial section be constructed followed by construction of an overlay after completion of

the construction operations. If portions of the roadway will have repetitive truck traffic, we

recommend the asphalt concrete layer be a minimum of four (4) inches in these areas. We are

available to discuss this with you as the project progresses.

Although structural numbers for twenty (20) year design life calculations were used in our

analysis, our experience in the area indicates that an overlay or other roadway reconditioning

strategy will likely be required in ten (10) to fifteen (15) years after the initial pavement

construction date. This is in part due to the very high rate of freeze-thaw cycles and high

ultraviolet exposure that southwestern Colorado receives.

PN: 53088GE

July 15, 2013

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6.0 CONSTRUCTION MONITORING AND TESTING

Construction monitoring including engineering observations and materials testing during

construction is a critical aspect of the geotechnical engineering contribution to any project.

Unexpected subsurface conditions are often encountered during construction. If the subsurface

conditions encountered during construction are different than those that were the basis of the

geotechnical engineering report then modifications to the design may be implemented prior to

placement of asphalt pavement materials.

Compaction testing of fill material should be performed throughout the project construction so

that the engineer and contractor may monitor the quality of the fill placement techniques being

used at the site. We are available to monitor compaction of the pulverized roadway section,

provide unconfined compressive strength tests of samples from the pulverized and treated

section, and perform asphalt testing during placement of the asphalt mat. We are available to

develop a testing program for soil, aggregate materials, and asphaltic concrete for this project.

7.0 CONCLUSIONS AND CONSIDERATIONS

The information presented in this report is based on our understanding of the proposed

construction that was provided to us and on the data obtained from our field and laboratory

studies. We recommend that we be contacted during the design and construction phase of this

project to aid in the implementation of our recommendations. Please contact us immediately if

you have any questions, or if any of the information presented above is not appropriate for the

proposed site construction.

The recommendations presented above are intended to be used only for this project site and the

proposed construction which was provided to us. The recommendations presented above are not

suitable for adjacent project sites, or for proposed construction that is different than that outlined

for this study.

Our recommendations are based on limited field and laboratory sampling and testing.

Unexpected subsurface conditions encountered during construction may alter our

recommendations. We should be contacted during construction to observe the exposed

subsurface soil conditions to provide comments and verification of our recommendations.

We are available to review and tailor our recommendations as the project progresses and

additional information which may influence our recommendations becomes available.

PN: 53088GE

July 15, 2013

12

Please contact us if you have any questions, or if we may be of additional service.

Respectfully submitted, TRAUTNER GEOTECHTRAUTNER GEOTECHTRAUTNER GEOTECHTRAUTNER GEOTECH LLC LLC LLC LLC

Thomas R. Harrison II, P.E.

Staff Geotechnical Engineer

PN: 53088GE May 6, 2013

APPENDIX A

Field Study Results

07-1

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LOG OF BORING 3RD TB-1

PN:53088GEMr. Jim Ketter, PE, KPMC

Mr. Alex Carter, SuperintendentPhase II, Design Level

Montezuma-Cortez High School

Depthin

feet

0

1

2

3

4

5

DESCRIPTION

Sample TypeMod. California Sampler

Bag Sample

Standard Split Spoon

Water LevelWater Level During Drilling

Water Level After Drilling

MAN-PLACED FILL MATERIAL, GRAVEL, CLAY, medium dense, brown to tan

CLAY, sandy, stiff, dry to slightly moist, brown to tan

Bottom of test boring at four (4) feet

US

CS

GC

CL

GR

AP

HIC

Sam

ples

Blo

w C

ount

Wat

er L

evel

REMARKS

Field Engineer : T. HarrisonHole Diameter : 6" solidDrilling Method : Continuous Flight AugerSampling Method : BulkDate Drilled : 07/02/2013Total Depth (approx.) : 4 feetLocation : See Figure in Report

07-1

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Depthin

feet

0

1

2

3

4

5

DESCRIPTION


Bag Sample




US

CS

GR

AP

HIC

Sam

ples

Blo

w C

ount

Wat

er L

evel

REMARKS

SAND, clayey, few gravels, medium dense, dry to slightly moist, brown to tan

WEATHERED FORMATIONAL MATERIAL, Dakota Sandstone Formation, medium hard, dry, tan


SC

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Depthin

feet

0

1

2

3

4

5

DESCRIPTION


Bag Sample




US

CS

GR

AP

HIC

Sam

ples

Blo

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ount

Wat

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REMARKS




SC

07-1

2-20

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Depthin

feet

0

1

2

3

4

5

DESCRIPTION


Bag Sample




US

CS

GR

AP

HIC

Sam

ples

Blo

w C

ount

Wat

er L

evel

REMARKS

SAND, clayey, few gravels, medium dense, slightly moist, brown to tan

WEATHERED FORMATIONAL MATERIAL, Dakota Sandstone Formation, medium hard, dry, brown to tan

FORMATIONAL MATERIAL, medium hard, dry, brown to tan


SC

PN: 53088GE May 6, 2013

APPENDIX B

Laboratory Test Results

Project No. :

Figure:Date:

DR

Y D

EN

SIT

Y (P

CF)

MOISTURE CONTENT (%)

0 5 10 15 20 25 30 3580

85

90

95

100

105

110

115

120

125

130

135

140

145

2.62.72.8

Zero Air Voids forSpecific Gravity

Project:

Sample Source:

Sample Description:

Test Method:

Maximum Dry Density:

Optimum Moisture Content:

Laboratory Number:

MCHS Pahse II-3rd Street Extension

Bulk - Subgrade

ASTM D1557 Method C

129.0 pcf

9.0 %

11295-A

53088GE

Bulk

7/3/13

(no specification provided)

PL= LL= PI=

USCS= AASHTO=

D85= D60= D50=D30= D15= D10=Cu= Cc=

*

SC - Clayey sand#4#10#40

#200

100969040

12 21 9

SC A-4(0)

0.3134 0.1305 0.0980

7-16-13 G. Jadrych

11295-A Bulk 7-3-13

R. Barrett Engineer Tech.

Mr. Jim Ketter Owners Rep.

Cortez High School District RE-1

53088GE

Material Description

Atterberg Limits (ASTM D 4318)

Classification

Coefficients

Date Tested: Tested By:

Remarks

Sample No.: Source of Sample: Date Sampled:Location: Elev./Depth:

Checked By: Title:

Client:

Project:

Project No: Figure

SIEVE PERCENT SPEC.* PASS?

SIZE FINER PERCENT (X=NO)

PE

RC

EN

T F

INE

R

0

10

20

30

40

50

60

70

80

90

100

GRAIN SIZE - mm.

0.0010.010.1110100

% +3"Coarse

% Gravel

Fine Coarse Medium

% Sand

Fine Silt

% Fines

Clay

0 0 0 4 6 50 40

6 in

.

3 in

.

2 in

.

1½

in.

1 in

.

¾ in

.

½ in

.

3/8

in.

#4

#1

0

#2

0

#3

0

#4

0

#6

0

#1

00

#1

40

#2

00

Particle Size Distribution Report

geotechnical engineering pavement section thickness...

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