Pavement and Materials Report .pdf

WY FLAP 740(1) Skyline Drive and Lower Fremont Lake Road

PAVEMENT AND MATERIALS REPORT

January 2022

Report Prepared By

U.S. Department of Transportation Federal Highway Administration

Central Federal Lands Highway Division Lakewood, Colorado ii

Written by: ________________________________________________________ Marty Fey, Pavements & Materials Engineer

Reviewed and approved for distribution by:

Mike Voth, Pavements and Materials Team Lead

Distribution:

Project Development Project Management Construction Materials Pavements Geotech iii

TABLE OF CONTENTS

I. INTRODUCTION

II. CLIMATE

III. EXPLORATION

IV. EXISTING PAVEMENT & SOILS

V. PAVEMENT DESIGN CALCULATION INPUTS

VI. PAVEMENT RECOMMENDATIONS & DISCUSSION

VII. MATERIALS RECOMMENDATIONS

APPENDICES

A – Location Map B – Laboratory Reports and Boring Log C – Photographs D – AASHTO ’93 Flexible Pavement Design E – PG LTPPBIND Software F – Preliminary Pavement Recommendation Memo

I. INTRODUCTION

This report is written to provide pavement and materials recommendations for Skyline Drive and Lower Fremont Lake Road project located in Sublette County, north of Pinedale, WY. See Appendix A for location map.

Lower Fremont Lake Road, also known as FS 111, begins at the intersection with Skyline Drive and leads to the boat ramp and parking area for Fremont Lake. Proposed improvements for Lower Fremont Lake Road include rehabilitation of the existing gravel roadway to provide 24’ uniform roadway width including paving for 1.47 miles and approach road realignment at two locations.

Skyline Drive is a continuation of a previous CFLHD FLAP project. The project resumes work on Skyline Drive just north of the turnoff to the ski area and ends at the top where the route meets with the parking lots and camping loop. For Skyline Drive, proposed improvements include rehabilitation of the existing roadway to provide 22’ uniform roadway width, spot widening to provide pull out areas and minor flattening of S-curves where terrain allows widening without significant earthwork. The project also includes full depth reclamation and paving of Skyline Drive from the end of the previous project (Sta. 366+21) north for 4.2 miles to the parking area for the Elkhart Park Trailhead.

The Preliminary Pavement Recommendations Memo was issued in September 2021. The memo provided the pavement recommendations as well as the proposed pay items. This memo is found in Appendix F. The pavement recommendations have been finalized and are discussed in Part VI of this report.

II. CLIMATE

Climate data was obtained from noaa.gov. This data is summarized in Table 1 below.

The average annual precipitation for this area is approximately 11.70 inches. The project is in a mountainous area and at an elevation that receives both snow and rain, dependent upon the time of year.

Table 1: Weather Data

Month Average

HIGH (°F)

Average

LOW (°F)

Average

MEAN (°F)

Average PRECIP. (in)

January 26.7 2.2 14.4 0.57 February 28.6 1.8 15.2 0.64

March 37.8 11.8 24.8 0.53 April 49.5 21.0 35.3 0.76 May 59.4 27.5 43.4 1.66 June 69.0 34.4 51.7 1.26 July 77.8 39.4 58.6 0.96

August 76.8 37.7 57.3 1.22 September 67.0 30.1 48.5 1.74

October 53.8 22.5 38.1 0.84 November 36.7 11.2 24.0 0.77 December 26.2 2.2 14.2 0.75

III. EXPLORATION

On October 13th, 2020 CFLHD pavement & material engineer Marty Fey completed a field investigation which included boring and subgrade sampling. Vine Laboratories was hired through the CFLHD BPA to assist with the field investigation. A CME 55 truck-mounted drill rig with a 6” O.D. auger was used to complete the borings. Pavement borings were logged at 18 locations and subgrade samples were collected and tested in the laboratory. CFL personnel logged the borings; this included depth of boring, visual soil classification, and pavement thickness when applicable. Boring locations, test results, and other information is shown in Appendix B.

IV. EXISTING PAVEMENT & SOILS

The existing roadway of Skyline Drive was observed to consist of old, oxidized asphalt pavement with high severity fatigue cracking extending throughout the length of the project. Full depth reclamation is recommended for this portion of the project. Pavement thickness was found to be 2 to 4 inches in depth at the locations drilled, supported by 0 to 3 inches of aggregate road base.

Lower Fremont Lake Road consists of a gravel roadway surface with 3.5 to 4 inches of pulverized asphalt and aggregate surfacing on top of native subgrade. The structure of the roadway is holding up well but suffers from severe wash boarding and other surface issues.

Drilling efforts were relatively easy. The subgrade materials encountered are of moderate quality. The subgrade soils encountered consisted primarily of silty sands to sandy clays and were classified primarily as A-2-4(0) and A-1-b(0). Subgrade soils exhibited low plasticity and had R-values of 29 to 72. Resistivity values were found to be moderate and indicate a lower risk of sulfate and chloride attack. See the laboratory reports and boring logs in Appendix B for more information.

Because this project is located in a mountainous area, boulders and cobbles may be encountered during construction.

V. PAVEMENT DESIGN CALCULATION INPUTS

Design Parameters

Traffic counts for both roadways were provided with the FLAP application and were used to develop ESAL estimates.

For Skyline Drive, an average daily traffic (ADT) of 200 and a truck factor of 20% class 5, resulted in a calculated cumulative equivalent single axel load (ESALs) of 91,000 for a 20-year period.

For Lower Fremont Road, an average daily traffic (ADT) of 300 and a truck factor of 20% class 5, resulted in a calculated cumulative equivalent single axel load (ESALs) of 155,000 for a 20-year period.

The assumptions made in the ESAL calculations as well as related design factors are included in Appendix D. Design factors used in the ESALs calculations as well as the structural coefficients were taken from the CFLHD Project Development Design Manual (PDDM), Chapter 11.

Roadbed Soil Resilient Modulus

The soil resilient modulus was converted from R-Values, AASHTO T 190, using the following equation:

Resilient Modulus (psi) = 10[ ( S

+ 18.72 ) / 6.24 ] where S1 = [(R-Value – 5) / 11.29] + 3

The average R-value on Skyline drive was found to be 51. However, due to high variability in in the subgrade, a lower R-value was selected to generate a design resilient modulus of 8,000 psi.

Lower Fremont Lake Road was found to have relatively high R-values resulting in a resilient modulus of 21,000. For design purposes the AASHTO recommended maximum resilient modulus of 15,000 was used.

VI. PAVEMENT RECOMMENDATIONS & DISCUSSION

Utilizing AASHTO 93 Flexible Pavement Design (Appendix D), a 20-year pavement design required a Calculated Design Structural Number (SN) of 2.04 and 1.75, for Skyline Drive and Lower Fremont Lake Road respectively. After evaluating alternatives and performing various iterations, the following are the recommended pavement structural sections:

Table 2: Recommended Pavement Section, Skyline Drive Layer Thickness

HACP 3 inches (two lifts) Full Depth Reclamation (FDR) or Aggregate Base Course in widened/reconstructed areas

6 inches

SN = 2.04

Table 3: Recommended Pavement Section, Lower Fremont Lake Road

HACP 3 inches (two lifts) Aggregate Base Course 4 inches

SN = 1.80

Existing surfacing aggregate on Lower Fremont Lake Road may be reused as aggregate base course to reduce imported aggregate quantities.

VII. MATERIALS RECOMMENDATIONS

Selection of Asphalt Binder

LTPPBind software was utilized to assist in the selection of asphalt binder. The information presented in LTPPBind is shown in Appendix E. LTPPBind indicated that a PG 58-34 binder should be used. Consideration was given to the location of the project as well as performance of past projects in similar conditions.

Prime and Tack Coats, Blotter and Fog Seal

Prime Coat and Blotter are recommended for this project. A tack coat applied between pavement lifts is recommended. It is also recommended that a fog seal be applied to the final surfacing.

Drainage and Subexcavation

During the field investigation, areas of pavement distress were present. Most appeared to be caused due to fatigue and age. Two areas of moderate distress were observed and are addressed in a separate geotech report. No major water damage or drainage problems pertaining to the existing traveled way were observed. If any drainage issues are encountered, the scope of the project allows for partial reconstruction. A quantity of 500 cubic yards of subexcavation should be included in the contract. This quantity should remain in the Contract in the event that areas in need of repair are encountered.

Bid Items

Suggested FP-14 pay items for the proposed structural section are shown in Table 4 below.

Table 4: Recommended Pay Items Item Number Item Description Unit

20402-0000 Subexcavation CUYD

30202-2000 Roadway Aggregate, Method 2 TON

30401-5300 Full Depth Reclamation, Method 2, 6-inch SQYD

40101-0600 Asphalt Concrete Pavement, Gyratory Mix, ½” Nominal Max Size Aggregate, 0.3 to < 3 Million ESAL

TON

40105-3000 Antistrip Additive, Type 3 TON

40601-0000 Fog Seal SQYD

41101-1000 Prime Coat, Method 1 SQYD

41105-0000 Blotter TON

41201-0000 Tack Coat SQYD

APPENDICES

A – Location Map

B – Laboratory Reports and Boring Log

C – Photographs

D – AASHTO ’93 Flexible Pavement Design

E – PG LTPPBind Software

F – Preliminary Pavement Recommendation Memo

Appendix A: Location Map

Appendix B: Laboratory Reports and Boring Logs

Project:

Sample Number

Station or Location

Offset from CL

Date Sampled

Depth of Bore

Container Type

Pavement/ABC Thickness R-Value Class Liquid

Limit/PI Resistivity, ohm.cm pH Sulfate % Chloride %

0 to 4"

4" to 7" SM / A-2-4(0) 7" to 5'

0 to 3"

3" to 5"

5" to 3'

3' to 5' Sand Silty, Dark Brown 0 to 3"

3" to 5"

5" to 5'

0 to 2"

2" to 3.5" SM / A-1-b(0) 3.5" to 3.5'

3.5' to 5'

0 to 2.5"

2.5" to 5.5" SM / A-2-4(0) 5.5" to 5'

0 to 2"

2" to 4.5" 61 SM / A-1-b(0) 4.5" to 5'

0 to 2"

2" to 4"

4" to 5'

0 to 2.5"

2.5" to 4" 66 SM / A-2-4(0) 4" to 5'

0 to 2.5"

2.5" to 5' SM / A-2-4(0)

0 to 3"

3" to 5.5' 70 SP-SM / A-1-b(0) 5.5' to 20'

0 to 3"

3" to 4'

4' to 5'

0 to 3"

3" to 4.5'

4.5' to 9.5'

9.5' to 15.5'

0 to 3"

3" to 5'

0 to 4"

4" to 5' 72 SM / A-1-b(0)

54 NV / NP

17 / 1

NV / NP

NV / NP

NV / NP

NV / NP

NV / NP

SM / A-2-4(0)

SM / A-2-4(0)

Sand Silty, Brown NV / NP

B-1 5' 5-gal bucket

10/13/2020 5' 5-gal bucket Classification, R-Value4' Rt

Asphalt

Asphalt

Sand to Sand Silty, Brown Sand Silty, Brown

Asphalt Sand Silty, Brown

Aggregate Base Course, Brown

2' Rt Clay Sandy, Brown

B-12

3' Lt 10/13/2020 5'

15.5' 5-gal bucket 10/13/2020

Sand Silty, Brown

Sand Silty, Brown

Classification, R-Value

5' Lt 10/13/2020 5' 5-gal bucket

Asphalt

4" / 3"

3" / 2"

Classification, R-Value

Classification, Resistivity and pH

Cobbles @ 2 to 3.5'

Aggregate Base Course, Brown Sand Silty, Light Brown

5-gal bucket

10/13/2020

Asphalt

5' 2" / 1.5"

2.5" / 3"

5' 5-gal bucket Classification, R-Value

Aggregate Base Course, Brown

Sand Silty, Light Brown

Cobbles @ 1 to 2' and 4 to 5' 3" / 2"

Sand Silty, Brown

Comments

Cobbles @ 2.5 to 4'

Testing Requested

WY FLAP 704(1) Skyline Drive and Lower Fremont Road Contractor:

Logged By: Equipment:Sampled By:Marty Fey Marty Fey

10/13/20204' Rt

Boring Observations (grey = sample depth )

Asphalt Aggregate Base Course, Brown Sand Silty, Brown

Asphalt B-3 3' Lt 10/13/2020

B-4 3.5' Rt 10/13/2020

Asphalt Classification

Very Moist and Soft, Water @ 18'

5'

B-6

B-5

5-gal bucket

4' Lt

Asphalt

ClassificationSand Silty, Brown

Sand Silty, Light Brown

B-7 2.5' Lt 10/13/2020

B-2 4' Lt 10/13/2020 5' 5-gal bucket

Asphalt

Classification Aggregate Base Course, Brown Sand Silty, Brown

5' 5-gal bucket

Asphalt ClassificationAggregate Base Course, Brown

Sand Silty, Brown

5-gal bucket

Asphalt Classification

5-gal bucket

Classification, R-Value20'

B-11

B-9 3' Lt 10/13/2020 5' 5-gal bucket

Asphalt

Sand Silty, Brown Gravel Sandy, Brown

B-10 10/13/20204' Rt

B-13 4' Lt 10/13/2020 5' 5-gal bucket Classification, Resitivity and pH Cobbles @ 1 to 2' and 3 to

3.5'

B-14 Classification, R-Value

2" / 2.5"

2" / 2"

2.5" / 0"

3" / 0"

3" / 0"

3" / 0"

3" / 0" 12,600

SM / A-1-b(0)

SM / A-4(0)

SM / A-2-4(0)

4" / 0"

19 / 2

13,260 7.1

CME 55 truck mounted (6"O.D. SSA)

Vine

Pavement Investigation - Shallow Borings and Cores - Log & Sampling Summary

B-8 3.5' Rt 10/13/2020 5' 5-gal bucket

Asphalt Classification, R-ValueAggregate Base Course, Brown

Sand Silty, Brown

6.1

Aggregate Base Course, Brown Sand Silty, Brown

2.5" / 1.5"

58 SM / A-2-4(0)

Cobbles @ 2.5 to 5'

Cobbles @ 4.5 to 13'

NV / NP

NV / NP

29 20 / 3

19 / 3

Sample Number

Station or Location

Offset from CL

Date Sampled

Depth of Bore

Container Type

Pavement/ABC Thickness R-Value Class Liquid

Limit/PI Resistivity, ohm.cm pH Sulfate % Chloride %CommentsTesting RequestedBoring Observations (grey = sample depth )

0 to 3.5"

3.5" to 5' 67 SM / A-2-4(0)

0 to 4"

4" to 5' SM / A-2-4(0)

0 to 4"

4" to 5' 64 SP / A-1-b(0)

0 to 4"

4" to 5'

650 6.1 0.009 0.0631Sand Silty, Brown

B-103 2' Rt 10/13/2020 5' 5-gal bucket

Aggregate Base Course, Brown Classification, R-Value 0" / 4" NV / NPSand, Brown

NV / NPSW-SM / A-1-b(0)

NV / NP

B-102 1' Rt 10/13/2020 5' 5-gal bucket

Aggregate Base Course, Brown Classification, Resitivity and pH, Sulfates and

Chlorides

0" / 4" NV / NP

B-101 1' Rt 10/13/2020 5' 5-gal bucket

Aggregate Base Course, Brown Classification, R-Value 0" / 3.5"Sand Silty, Brown

10/13/2020 5' 5-gal bucket

Aggregate Base Course, Brown ClassificationSand, Brown B-104 1' Lt 0" / 4"

Appendix C: Photographs

Photo 1: View of Fremont Lake from Skyline Drive

Photo 2: Drilling, B-1

Photo 3: Drilling, B-3

Photo 4: B-10, moderate roadway damage

Photo 5: B-12, moderate roadway damage

Photo 6: Lower Fremont Lake Road

Photo 7: Washboarding

Photo 8: Fremont Lake Road

Appendix D: AASHTO ’93 Flexible Pavement Design

AASHTO FLEXIBLE PAVEMENT DESIGN Skyline Drive Layer Thickness Determination Using Trial and Error

Layer Drainage Layer Layer No. Description Coefficient, ai Coefficient, mi Thickness, in SN

(topmost) Layer 1 AC Layer 0.44 1.00 3.00 1.32 Layer 2 FDR 0.12 1.00 6.00 0.72 Layer 3 Gran. Subbase 0.12 1.00 0.00 0.00 Layer 4 Select Borrow 0.08 0.90 0.00 0.00 Layer 5 0.00 Layer 6 0.00 Layer 7 0.00

(bottommost) Layer 8 0.00 Subgrade Subgrade N/A N/A N/A N/A

AC Layer 401 = 0.44 Trial SN 2.04 403 = 0.40

CAB 301 = 0.14 Design SN to Match 2.04 Subbase/Minor agg 302 = 0.12 FDR 304 = 0.12 Design is sufficient Select borrow 204 = 0.06 to 0.08 (Refer to Exhibit 11.2-C in Chapter 11 of PDDM for additional guidance on coefficients)

AASHTO FLEXIBLE PAVEMENT DESIGN Skyline Drive SN Determination

Design Inputs W18 = 91,000 ESALs Applications Over Design Period Typ. Range 50k to 10 million

R = 75 % Reliability Typ. Range 75 to 95%

So = 0.49 Standard Deviation AASHTO Standard

MR = 8,000 psi Subgrade Resilient Modulus Typ. Range 3000 to 15000 psi

Pi = 4.2 Initial Serviceability Typ. Range 4.2 to 4.4

Pt = 2 Terminal Serviceability Typ. Range 2.0 to 3.0

DESIGN SN = 2.04

Skyline Dri

R-Value = 72 S1 = 8.934 MR = 27027 R-Value = 29 S1 = 5.126 MR = 6629

R‐Value Correlation to Resilient Modulus*

Only change the R-values in C4 or C5. The rest is automatically calculated.

*CDOT method. Similar to results from Figure FF.6 in Volume 2 of AGDPS and used by CFLHD.

Skyline Drive

AADT 200 Annual Growth 0.02 Design Years 20

Directional Distribution

0.5

Lane Distribution

Classification Percent Truck

Factor Growth Factor ADT Yr 1

Design Lane

ESALs ADT at N

Autos 65.0% 0.0006 130 0 193 Values Pickups, Vans 14.9% 0.004 24.29737 30 529 44

297 (calculated) Class 4 buses 0.0% 1.5 24.29737 0 0 0 200 Class 5 trucks/RVs 20.0% 0.5 24.29737 40 88685 59 2019 Class 6 0.0% 1 24.29737 0 0 0 2039 Class 8 0.1% 1.5 24.29737 0 1330 0

2 Class 9 0.0% 2 24.29737 0 0 0 100.00% 90544 297

(refer to Exhibit 11.2‐A in the PDDM for additional guidance on truck factors)

GR = Growth Rate (%)

Future ADT Calculation ADTf = ADTi (1 + GR)(F‐I)

ADTf = Average daily traffic for future year ADTi = Average daily traffic for initial year

I = Initial year for ADT F = Future year for ADT

AASHTO FLEXIBLE PAVEMENT DESIGN Freemont Lake Road Layer Thickness Determination Using Trial and Error

Layer Drainage Layer Layer No. Description Coefficient, ai Coefficient, mi Thickness, in SN

(topmost) Layer 1 AC Layer 0.44 1.00 3.00 1.32 Layer 2 FDR 0.12 1.00 4.00 0.48 Layer 3 Gran. Subbase 0.12 1.00 0.00 0.00 Layer 4 Select Borrow 0.08 0.90 0.00 0.00 Layer 5 0.00 Layer 6 0.00 Layer 7 0.00

(bottommost) Layer 8 0.00 Subgrade Subgrade N/A N/A N/A N/A

AC Layer 401 = 0.44 Trial SN 1.80 403 = 0.40

CAB 301 = 0.14 Design SN to Match 1.75 Subbase/Minor agg 302 = 0.12 FDR 304 = 0.12 Design is sufficient Select borrow 204 = 0.06 to 0.08 (Refer to Exhibit 11.2-C in Chapter 11 of PDDM for additional guidance on coefficients)

AASHTO FLEXIBLE PAVEMENT DESIGN Freemont Lake Road SN Determination

Design Inputs W18 = 155,000 ESALs Applications Over Design Period Typ. Range 50k to 10 million

R = 75 % Reliability Typ. Range 75 to 95%

So = 0.49 Standard Deviation AASHTO Standard

MR = 15,000 psi Subgrade Resilient Modulus Typ. Range 3000 to 15000 psi

Pi = 4.2 Initial Serviceability Typ. Range 4.2 to 4.4

Pt = 2 Terminal Serviceability Typ. Range 2.0 to 3.0

DESIGN SN = 1.75

Freemont L

R-Value = 67 S1 = 8.492 MR = 22953 R-Value = 64 S1 = 8.226 MR = 20809

R‐Value Correlation to Resilient Modulus*

Only change the R-values in C4 or C5. The rest is automatically calculated.

*CDOT method. Similar to results from Figure FF.6 in Volume 2 of AGDPS and used by CFLHD.

Freemont Lake Road

AADT 300 Annual Growth 0.02 Design Years 20

Directional Distribution

0.5

Lane Distribution

Classification Percent Truck

Factor Growth Factor ADT Yr 1

Design Lane

ESALs ADT at N

Autos 54.0% 0.0006 162 0 241 Values Pickups, Vans 25.0% 0.004 24.29737 75 1330 111

446 (calculated) Class 4 buses 0.0% 1.5 24.29737 0 0 0 300 Class 5 trucks/RVs 20.0% 0.5 24.29737 60 133028 89 2019 Class 6 0.0% 1 24.29737 0 0 0 2039 Class 8 1.0% 1.5 24.29737 3 19954 4

2 Class 9 0.0% 2 24.29737 0 0 0 100.00% 154313 446

(refer to Exhibit 11.2‐A in the PDDM for additional guidance on truck factors)

GR = Growth Rate (%)

Future ADT Calculation ADTf = ADTi (1 + GR)(F‐I)

ADTf = Average daily traffic for future year ADTi = Average daily traffic for initial year

I = Initial year for ADT F = Future year for ADT

Appendix E: PG LTPPBind Software

BindReport-5Closest.txt

Five Closest Weather Stations For Latitude/Longitude= 42.884/110.029 Report Date: 9/13/2021 (LTPPBind V3.0 Alpha)

WY FLAP 740(1) Skyline Drive and Lower Fremont Lake Road

General A=6 km B=12 km C=27 km D=41 km E=47 km Station ID WY2054 WY7260 WY6165 WY0695 WY0865 County/District sublette sublette sublette sublette sublette Weather Station cora 4 n pinedale merna big piney bondurant Elevation, m 2079 2032 2181 1932 1875 Latitude, Longitude 42.93 ,110 42.87 ,109.87 42.95 ,110.37 42.55 ,110.12 43.2 ,110.4 Last Year Data Available 1994 1997 1987 1997 1996

Air Temperature Mean ( Std, N ) Mean ( Std, N ) Mean ( Std, N ) Mean ( Std, N ) Mean ( Std, N ) High Temperature 27.3 (19,15) 28.2 (13,34) 25.9 (10,24) 29.1 (12,18) 28.8 (14,34) Low Temperature -34.5 (47,15) -34.8 (40,33) -31.8 (31,24) -36.2 (34,18) -41 (35,31) Low Temperature Drop 27.6 (29,15) 29.1 (29,33) 25.7 (22,24) 31.4 (34,18) 34.6 (30,31) Degree-Days > 10C 1627 (210,15) 1836 (166,34) 1401 (138,24) 1947 (192,18) 1877 (226,34)

PG High Low Rel. High Low Rel. High Low Rel. High Low Rel. High Low Rel.

Pavement Temperature, C 43.4 -25.0 45.7 -25.2 40.9 -23.1 46.8 -26.1 46.1 -29.8 50% Reliability PG 46-28 (98,77) 46-28 (61,78) 46-28 (98,94) 52-28 (98,72) 52-34 (98,90) >50% Reliability PG 46-34 (98,98) 52-28 (98,78) 46-34 (98,98) 52-34 (98,98) 52-40 (98,98) = 52-34 (98,98)

Appendix F: Preliminary Pavement Recommendation Memo

Subject: Preliminary Pavement & Materials Recommendations (V1)

From: Marty Fey Pavement & Materials Engineer, CFLHD

Through: Mike Voth Pavement & Materials Team Lead, CFLHD

To: Tom Sohn, Project Manager, CFLHD Jeff Felling, Design Engineer, CFLHD

INTRODUCTION

This memorandum provides preliminary pavement and material recommendations for the Skyline Drive and Lower Fremont Lake Road project located in Sublette County, north of Pinedale, WY.

Lower Fremont Lake Road, also known as FS 111, begins at the intersection with Skyline Drive and leads to the boat ramp and parking area for Fremont Lake. Proposed improvements for Lower Fremont Lake Road include rehabilitation of the existing gravel roadway to provide 24’ uniform roadway width including paving for 1.47 miles and approach road realignment at two locations.

Skyline Drive is a continuation of a previous CFLHD FLAP project. The project resumes work on Skyline Drive just north of the turnoff to the ski area and ends at the top where the route meets with the parking lots and camping loop. For Skyline Drive, proposed improvements include rehabilitation of the existing roadway to provide 22’ uniform roadway width, spot widening to provide pull out areas and minor flattening of S-curves where terrain allows widening without significant earthwork. The project also proposes paving of Skyline Drive from the end of the previous project (Sta. 366+21) north for 4.2 miles to the parking area for the Elkhart Park Trailhead.

CFLHD standards and guidelines were used to complete the pavement and materials recommendations.

Technical Memorandum

Date: September 13, 2021

FIELD INVESTIGATION

On October 13th, 2020 CFLHD pavement & material engineer Marty Fey completed a field investigation which included boring and subgrade sampling. Vine Laboratories was hired through the CFLHD BPA to assist with the field investigation. A CME 55 truck-mounted drill rig with an 6” O.D. auger was used to complete the borings. Pavement boring were logged at 18 locations, subgrade samples were collected and tested in the laboratory. See the attached boring and testing logs for more detailed information.

The primary objectives of this field investigation were as follows:

Measure and record existing pavement and subgrade layer depths;

Gather subgrade soil samples for follow-up testing to determine engineering properties;

Evaluate and record pavement distress conditions;

Evaluate roadway and project area for constructability concerns.

The existing roadway of Skyline Drive was observed to consist of old, oxidized asphalt pavement with high severity fatigue cracking extending throughout the length of the project. This roadway would be a good candidate for full depth reclamation.

Lower Fremont Lake Road consists of a gravel roadway surface consisting of pulverized asphalt and aggregate surfacing. The structure of the roadway is holding up well but suffers from severe wash boarding and other surface issues.

The information gathered as described above was used to support pavement rehabilitation, structural design, and material recommendations.

Below are summary tables of data gathered and test results. For more complete and detailed results, see the attached logs and lab test reports.

Summary of Sampling & Test Results

Pavement Depth

Roadbase

Depth R-value, subbase

R-value, subgrade Comments

0 to 4 inches

0 to 4 inches

N/A 29 - 70

Subgrade material consists primarily of Silty

Sands, A-2-4(0) and A-1-b(0).

Resistivity values on Fremont road are low and indicate an increased risk of sulfate and chloride attack. Additional chloride and sulfate testing was performed.

TRAFFIC:

Traffic counts were provided with the FLAP application and used to developed estimates for ESALs. The road is primarily used for recreational and residential access with little commercial use. Truck counts were based on engineering judgement and are assumed to be very low. The counts appear generally consistent with other historical traffic data and they align with what was experienced during the field investigation. The following is a summary of traffic data as well as the estimated ESALs used for design:

Skyline Drive Lower Fremont Road

2019 ADT 200 300

2039 ADT (2% growth) 297 446 2019 % Trucks 20% Class 5, 0.1% Class 8 20% Class 5, 1% Class 8 Directional Factor 50% 50% Design ESALs 91,000 155,000

DESIGN RECOMMENDATIONS

The pavement design, rehabilitation method, and other recommendations are included below.

In developing the pavement structural and rehabilitation recommendations the following criteria was used:

Design Criteria Skyline Drive Lower Freemont Lake

Road Initial Serviceability 4.2 4.2 Terminal Serviceability 2.0 2.0 Design Reliability Level 75% 75% Overall Standard Deviation 0.49 0.49 Soil Resilient Modulus 8,000 psi 15,000 psi Performance Period (4R) 20 years 20 years 20-year ESAL 91,000 155,000 Existing Borrow Material R-Value 30 65 Calculated Structural Number (SN) 2.04 1.75

The following are the recommended pavement structural sections:

Skyline Drive, Pulverize and Overlay

HACP 3 inches (two lifts) Full Depth Reclamation (FDR) or Aggregate Base Course in widened/reconstructed areas

6 inches

SN = 2.04

Lower Fremont Lake, Recondition and Overlay

Layer Thickness HACP 3 inches (two lifts) Aggregate Base Course 4 inches

SN = 1.75

Existing surfacing aggregate on Lower Fremont Lake Road may be reused as aggregate base course to reduce imported aggregate quantities.

The project is located in a mountainous area and numerous cobles were encountered during exploration. Cobbles and/or boulders will likely be encountered during construction.

ADDITIONAL RECOMMENDATIONS:

The asphalt binder grade should be PG 64-28. This aligns with recommendations from LTPPBind and local standards.

Include a nominal amount of subexcavation (~500 cu yd) to be used at discretion of the

CO.

Recommend the following bid items.

Item Number Item Description Unit 20402-0000 Subexcavation CUYD 30202-2000 Roadway Aggregate, Method 2 TON 30401-5300 Full Depth Reclamation, Method 2, 6-inch SQYD

40101-0600 Asphalt Concrete Pavement, Gyratory Mix, ½” Nominal Max Size Aggregate,

0.3 to < 3 Million ESAL

TON

40601-0000 Fog Seal TON 40605-0000 Blotter TON 41101-0000 Prime Coat TON 41201-0000 Tack Coat TON

CONSTRUCTION CONSIDERATIONS & SPECIAL CONTRACT PROVISIONS

CFLHD standard SCR’s related to pavements & materials will be used. If the decision is made to use a local borrow source and/or develop a source, an SCR may need to be developed.

Attachments:

Lab Test Reports Boring Logs & Charts LTPPBind Report Pavement Design