6706-A - CAPE BLANCO RUNWAY PAVEMENT REPORT .pdf

Pavement Design Report

Runway 14/32 Rehabilitation Cape Blanco State Airport (5S6)

Sixes, Oregon

December 9, 2022

(REVISED: 01/26/2023)

Prepared for

Century West Engineering 5500 Meadows Road, Suite 250

Lake Oswego, OR 97035

Prepared by

16520 SW Upper Boones Ferry Road, Suite 100 Tigard, OR 97224

(503) 641-3478 | www.gri.com

GRI 6706-A – Cape Blanco Airport Runway 14/32 Pavement Report Page i December 9, 2022 (Revised: 01/26/2023)

EXECUTIVE SUMMARY

I PROJECT DESCRIPTION

GRI completed a pavement investigation for the proposed improvements to Runway 14/32 at Cape Blanco State Airport (5S6) in Sixes, Oregon. Runway 14/32 is surfaced with asphalt concrete (AC) and is approximately 150 feet wide and 5,100 feet long. The purpose of our investigation was to evaluate the existing pavement condition, subsurface conditions, and pavement structural capacity along Runway 14/32 and provide design recommendations for rehabilitation and, if necessary, reconstruction. Our methodology and design recommendations are summarized in this report.

II PAVEMENT-DESIGN APPROACH AND METHODOLOGY

We completed our evaluation and the design analysis for pavement rehabilitation and reconstruction in general accordance with Federal Aviation Administration (FAA) Advisory Circulars 150/5370-11B, Use of Nondestructive Testing in the Evaluation of Airport Pavements, and 150/5320-6G, Airport Pavement Design and Evaluation. The pavement design analysis was conducted using Version 2.0.7 of the FAARFIELD (FAA Rigid and Flexible Iterative Elastic Layered Design) pavement-design software program. In accordance with the FAA guidelines, the structural analysis was conducted based on a minimum-20-year design period.

II.I Structural Life of Existing Pavement The structural life of existing pavement is calculated by the FAA design procedure based on the traffic-loading forecast, including growth rates, the structural properties of the existing pavement (thickness and modulus), and subgrade strength, as determined from investigation and testing of the pavement materials and subgrade soils. The structural life calculated in this manner only applies to the amount of time the existing pavement could support the forecasted traffic loading until its structural capacity decreases to the extent strengthening or reconstruction is required in order to avoid significant risk of structural damage to heavily loaded aircraft. Our analysis indicates that Runway 14/32 does not require structural strengthening to support the anticipated 20-year future traffic loading.

Since structural life does not account for deterioration in surface condition, pavement structures can have calculated structural lives exceeding 20 years, even though such life is not realistic from a surface-degradation standpoint.

In addition to a structural life evaluation using the proposed traffic mix, we also investigated the number of annual operations that can occur from some of the most damaging aircraft before the structural life is reduced to less than 20 years. We conducted three separate analyses to determine the maximum number of operations for the Cessna

GRI 6706-A – Cape Blanco Airport Runway 14/32 Pavement Report Page ii

Citation X, the Fokker 70, and the C-130. The results of our analyses indicate that the maximum number of operations that can occur before the structural life is reduced to 20 years are more than 50,000 operations for the Cessna Citation X, approximately 268 operations for the Fokker 70, or approximately 24 operations for the C-130.

III PAVEMENT-DESIGN RECOMMENDATIONS

As mentioned above, our analysis indicates that Runway 14/32 does not require structural strengthening to support the anticipated 20-year future traffic loading. Based on the type and frequency of surface distress we observed, we recommend at a minimum replacing the AC surfacing on the runway to improve the functional life and reduce the likelihood of foreign object debris (FOD) causing aircraft damage.

We have provided recommendations for performing partial-depth reconstruction (e.g., constructing a new pavement surface above the existing aggregate base) and full-depth reconstruction on Runway 14/32. We have also provided recommendations for rehabilitation with an overlay; however, this option carries a higher level of risk, as discussed within the report.

Our pavement recommendations are provided in Tables III-1 and III-2.

Table III-1: PAVEMENT DESIGN ALTERNATIVES FOR REHABILITATION

Design Thickness, inches

Cold Milling Pavement Removal(a) New AC (P-401) Surface (c)

Runway 14/32 – Overlay 0 2

Notes:

a. Pavement removal should be performed with a fine-toothed milling drum.

b. Use Oregon Department of Transportation (ODOT) Level 3, ½-inch dense asphalt concrete pavement with Performance Grade (PG) 64-22 binder.

c. Rehabilitation will result in a 2-inch grade increase.

d. Tack coat should be placed on a cleaned surface prior to the AC overlay.

e. This option carries significant risks associated with premature reflective cracking.

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Table III-2: PAVEMENT DESIGN ALTERNATIVES FOR PARTIAL- AND FULL-DEPTH RECONSTRUCTION

Design

Thickness, inches

AC (P-

401)

AC Stabilization Layer (P-403)

Aggregate Base

(AB) (P-209)

Approximate Remaining Existing AB

3-Inch Thick Partial-Depth Reconstruction 3 -- -- 15¾

4-Inch Thick Partial-Depth Reconstruction 4 -- -- 14¾

Full-Depth Reconstruction with Stabilized Base 4 5 6 --

Full-Depth Reconstruction without Stabilized Base 4 -- 12½ --

Notes:

a. A 3-inch partial-depth reconstruction provides structural capacity to accommodate the expected traffic loading for approximately 17 years.

b. Approximate remaining existing AB represents the average existing AB thickness remaining after removing the upper 4 inches of existing material.

c. Minimum and maximum lift thicknesses for AC placement should be 2 inches and 3 inches, respectively.

d. Use ODOT Level 3, ½-inch dense asphalt concrete pavement with Performance Grade (PG) 64-22 binder.

e. We recommend placing a non-woven Class 2 geotextile between the existing soil and an AB layer.

f. Exposed subgrade material should be compacted to meet FAA requirements prior to placement of AB.

IV DURATION OF REHABILITATION RECOMMENDATIONS

If the recommended rehabilitation or reconstruction work is not accomplished prior to the year 2026, our recommendations should be reevaluated to determine if modifications are necessary to account for additional deterioration of the pavement condition and the increase in traffic loading over the design period.

GRI 6706-A – Cape Blanco Airport Runway 14/32 Pavement Report

TABLE OF CONTENTS

I PROJECT DESCRIPTION ..................................................................................................... I II PAVEMENT-DESIGN APPROACH AND METHODOLOGY ................................................ I

II.I Structural Life of Existing Pavement .......................................................................................................... i III PAVEMENT-DESIGN RECOMMENDATIONS ................................................................... II IV DURATION OF REHABILITATION RECOMMENDATIONS ............................................. III

1 INTRODUCTION AND PROJECT DESCRIPTION

1.1 General

1.2 Project Description

2 SITE CONDITIONS

2.1 General

2.2 Subsurface Conditions

2.3 Dynamic Cone Penetration Testing

2.4 Groundwater

2.5 Existing Pavement Conditions

2.6 Falling Weight Deflectometer

3 PAVEMENT DESIGN AND RECOMMENDATIONS

3.1 Design Methodology and Input Parameters

3.2 Structural Life

3.3 Pavement Design Results

3.4 Pavement Design Recommendations

3.5 Pavement Classification Rating

4 CONSTRUCTION CONSIDERATIONS

4.1 General

4.2 Discussion of Subgrade Conditions

4.3 Subgrade Preparation and Parameters for New Pavement Design

4.4 Frost Considerations

4.5 General Construction Considerations

5 DESIGN REVIEW AND CONSTRUCTION SERVICES

6 LIMITATIONS

7 REFERENCES

TABLES

Table III-1: Pavement Design Alternatives for Rehabilitation ................................................................. ii Table III-2: Pavement Design Alternatives for Partial- And Full-Depth Reconstruction .............. iii Table 3-1: Structural Life Evaluation for Cessna Citation X Table 3-2: Structural Life Evaluation for Fokker 70 Table 3-3: Structural Life Evaluation for C-130 Table 3-4: Pavement Design Alternatives For Partial- and Full-Depth Reconstruction Table 3-5: Pavement Classification Rating Results Table 4-1: Recommended Material Specifications

FIGURES

Figure 1: Vicinity Map Figure 2: Site Plan

APPENDICES

Appendix A: Field Explorations and Laboratory Testing Appendix B: Falling Weight Deflectometer Test Results Appendix C: Aircraft Traffic Analysis Appendix D: Pavement Design Analysis and Calculation Worksheets Appendix E: Pavement Classification Rating Analysis

GRI 6706-A – Cape Blanco Airport Runway 14/32 Pavement Report Page 1

1 INTRODUCTION AND PROJECT DESCRIPTION

1.1 General

As requested, GRI completed a pavement investigation for Runway 14/32 at Cape Blanco State Airport (5S6) in Sixes, Oregon. The general location of the site is shown on the Vicinity Map, Figure 1.

1.2 Project Description

Runway 14/32 at Cape Blanco Airport is currently surfaced with asphalt concrete (AC) and is approximately 150 feet wide and 5,100 feet long. The airport is mainly utilized by general aviation aircraft; however, it is anticipated that larger aircraft may utilize the airport in the future. We understand that improvements are planned at the Cape Blanco Airport that includes rehabilitation or reconstruction of Runway 14/32 using AC, with the goal of improving the structural condition of the runway to support the projected aircraft operations for the next 20 years. The project limits include the full length and width of Runway 14/32, as presented on the Site Plan, Figure 2.

We based the structural analysis on our field explorations described in Appendix A, falling weight deflectometer (FWD) deflection testing summarized in Appendix B, traffic-loading analysis presented in Appendix C, pavement-design calculations in Appendix D, and pavement classification rating (PCR) calculations in Appendix E.

2 SITE CONDITIONS

2.1 General

Subsurface materials and conditions at the site were investigated on August 18, 2022, with eight full-depth pavement boring explorations, designated B-1 through B-8. Full-depth pavement cores were advanced to depths of approximately 7½ feet below ground surface (BGS). We retained the pavement core samples, collected disturbed samples of the aggregate material, and collected soil material samples using a standard split-spoon sampler within our pavement borings for further examination and testing in our laboratory.

Our explorations were conducted at the approximate locations shown on Figure 2. A discussion of the field-investigation and laboratory-testing programs completed for this investigation is provided in Appendix A. A summary of pavement core thickness and condition from our boring explorations is provided on Figure 1A. Logs of the explorations are provided on Figures 2A through 9A. Photographs of the pavement cores are shown on Figures 10A through 17A. The terms used to describe the materials encountered in the borings are defined in Table 1A and the symbols shown on the boring logs are defined on the attached legend. A summary of the lab testing results from our subsurface explorations is also provided in Table 2A in Appendix A.

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2.2 Subsurface Conditions

Results of our subsurface explorations suggest the existing AC thickness ranges from approximately 2¼ inches to 3¼ inches on Runway 14/32. Aggregate base (AB) was encountered at each full-depth exploration with thicknesses ranging from approximately 13½ inches to 18¾ inches. We encountered subgrade soils that generally consist of medium-dense silty sands with trace amounts of clay. Additional details of subsurface conditions encountered can be found on the boring logs in Appendix A.

2.3 Dynamic Cone Penetration Testing

GRI conducted dynamic cone penetration (DCP) testing along with the boring explorations on at all locations shown on Figure 2. Additional details regarding the DCP results are provided in Figures 18A through 25A in Appendix A.

2.4 Groundwater

The presence of groundwater was encountered at borings B-5 through B-8 at depths ranging from about 5¾ feet to 7½ feet BGS. A review of well logs in the vicinity of Cape Blanco Airport indicate groundwater levels at depths ranging from 6¾ feet to 13¾ feet BGS. Based on our current observations and understanding of the project site, we anticipate seasonal groundwater levels fluctuate, with shallower groundwater typically encountered during the wetter winter and spring months.

2.5 Existing Pavement Conditions

Based on our visual observations, the pavement on Runway 14/32 is in fair condition and exhibits widespread low-severity block cracking and longitudinal and transverse cracking, with some medium severity block cracking and longitudinal and transverse cracking. Many of the cracks appear to have been previously crack sealed, however there are numerous areas where the cracks have propagated through the crack seal.

2.6 Falling Weight Deflectometer

GRI conducted FWD testing on August 17, 2022, along the entire length of Runway 14/32.

The testing was conducted in accordance with Federal Aviation Administration (FAA) Advisory Circular 150/5370-11B, Use of Nondestructive Testing in the Evaluation of Airport Pavements, using our KUAB 2m Model 150 FWD device.

FWD testing was completed on Runway 14/32 along four test lines located at 7 feet east and west of the runway centerline and 40 feet east and west of the runway centerline. The tests were completed at approximately 200-foot intervals along the runway. The FWD test procedures are described in Appendix B, and the FWD deflection data is shown in Table 1B. The data were normalized to a 30,000-pound load basis.

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3 PAVEMENT DESIGN AND RECOMMENDATIONS

3.1 Design Methodology and Input Parameters

3.1.1 General

The design analysis for pavement rehabilitation and reconstruction was accomplished in general accordance with FAA Advisory Circulars 150/5370-11B and 150/5320-6G, Airport Pavement Design and Evaluation. The Advisory Circulars list a recommended design period for rehabilitation and reconstruction of 20 years.

The structural analysis was conducted using Version 2.0.7 of the FAARFIELD (FAA Rigid and Flexible Iterative Elastic Layered Design) pavement design software program. The input parameters used in the program were developed based on pavement boring explorations, summarized in Appendix A; FWD deflection test results, summarized in Appendix B; traffic-loading estimates, summarized in Appendix C; and the backcalculation analysis results, summarized in Appendix D.

3.1.2 Delineation of Analysis Units

We used the test results from our FWD test lines on Runway 14/32 to subdivide the data into four analysis units. Analysis units 1 through 4 correspond to the FWD test lines 7 feet east of the runway centerline, 7 feet west of centerline, 40 feet east of centerline, and 40 feet west of centerline, respectively.

3.1.3 Aircraft Traffic Mix

We used the aircraft fleet mix information provided by the project team for Cape Blanco Airport to formulate our aircraft traffic-loading estimate for use in our designs. The aircraft fleet mix was provided to us along with the annual operations for each aircraft in the fleet mix. The FAARFIELD program uses annual aircraft departures as the design input for analysis, consequently we assumed that annual departures are equal to 50% of the total annual operations for each aircraft provided to us by the project team. We forecasted the aircraft traffic mix over a 20-year design period according to FAA Advisory Circular 150/5320-6G and used an aircraft traffic growth rate of 0.5% based on discussions with the project team. The aircraft traffic mix used in our designs is provided in Table 1C of Appendix C. Additional details regarding our methodology to generate the aircraft traffic loading estimate is provided in Appendix C.

3.1.4 Backcalculation Analysis of FWD Test Data

We analyzed the FWD deflection data to backcalculate the equivalent elastic moduli of the pavement layers and subgrade soils at each test location. The moduli from the backcalculation were calculated using PAVBACK, our iterative, layered-elastic backcalculation analysis software. Details of the backcalculation procedure and a summary of results are presented in Table 1D in Appendix D.

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3.1.5 Design Subgrade Resilient Modulus Value for Reconstruction The subgrade resilient modulus used for design of rehabilitation and reconstruction options was estimated based on the backcalculation results from our FWD tests. In accordance with the procedures of FAA Advisory Circular 150/5320-6G, we developed the design resilient moduli for Runway 14/32 based on the average subgrade moduli minus one standard deviation for each analysis unit from the FWD backcalculation results. We used the backcalculated values from the FWD results to represent the upper subgrade modulus, which generally consists of medium-dense silty sands with trace amounts of clay.

Based on the backcalculation results and in accordance with the FAA design procedures, we determined the design moduli of the pavement layers for each analysis unit and converted those values to California bearing ratio (CBR) values. In general, we observed that the average moduli values for the AC and AB layers and the average minus one standard deviation moduli values for the subgrade for each analysis unit are consistent.

Due to the low variability across our results, we used the average or average minus one standard deviation of all the data points to determine our design moduli and CBR values.

We used a subgrade modulus value of 10,700psi for our design analyses, equivalent to a CBR of approximately 7.16. The design moduli of the pavement layers for each analysis unit are shown at the bottom of Table 1D in Appendix D. Further discussion of the methodology is provided in Appendix D.

3.2 Structural Life

The remaining pavement life of the existing airfield pavements, also referred to as “remaining structural life,” was estimated by the FAA evaluation procedure. The results are based on the current traffic loading, growth rates, structural properties of the existing pavement (thickness and modulus), and subgrade stiffness determined from investigation and testing of the pavement materials and subgrade soils and backcalculation analysis.

The FAARFIELD model used in our analysis and the calculated structural life of the pavement is presented on Figure 1D in Appendix D. Our results indicate the remaining structural life is approximately 23 years, which is more than the minimum-20-year structural life required by the FAA. Thus, structural strengthening is not required for Runway 14/32. Since structural life does not account for deterioration in surface condition, pavement structures can have calculated structural lives exceeding 20 years, even though such life is not realistic from a surface-degradation standpoint. As mentioned in this report, we observed widespread low- to medium-severity cracking that has a high potential for causing foreign object debris (FOD) damage to an aircraft; therefore, we recommend performing rehabilitation to improve the functional condition of the pavement.

In addition to a structural life evaluation using the proposed traffic mix, we also investigated the number of annual operations that can occur from some of the most

GRI 6706-A – Cape Blanco Airport Runway 14/32 Pavement Report Page 5 damaging aircraft before the structural life is reduced to less than 20 years. We conducted three separate analyses to determine the maximum number of operations for the Cessna Citation X, the Fokker 70, and the C-130. The results of our separate analyses for fleet mixes comprised of the Cessna Citation X, the Fokker 70, and the C-130 are presented in Tables 3-1 through 3-3, below.

Table 3-1: STRUCTURAL LIFE EVALUATION FOR CESSNA CITATION X

Aircraft Maximum Annual

Operations Calculated

Life Subgrade

CDF

HMA

CDF

Cessna Citation X >50,000 -- -- -- Abbreviations: CDF = Cumulative Damage Factor; HMA = Hot-Mix Asphalt

Table 3-2: STRUCTURAL LIFE EVALUATION FOR FOKKER 70

Aircraft Maximum Annual

Operations Calculated

Life Subgrade

CDF

HMA

CDF

Fokker 70 268 20.1 1.00 0.02

Table 3-3: STRUCTURAL LIFE EVALUATION FOR C-130

Aircraft Maximum Annual

Operations Calculated

Life Subgrade

CDF

HMA

CDF

C-130 24 20.6 0.97 0.00

3.3 Pavement Design Results

3.3.1 General

The FAARFIELD program was used to evaluate rehabilitation and reconstruction options for Runway 14/32 based on a 20-year design life using the aircraft traffic mix defined in Table 1C of Appendix C. Our rehabilitation and reconstruction analyses were performed based on the combined results from each analysis unit identified in the backcalculation results. The FAARFIELD outputs are provided in Appendix D.

3.3.2 Pavement Rehabilitation

Our pavement investigation indicated that the runway is comprised of approximately 2¾ inches of AC, on average. We observed full-depth cracking in six of our eight core explorations. Due to the thickness of AC and depth of cracking observed, we do not recommend a mill-and-inlay treatment on Runway 14/32, and the results of our investigation indicate that partial- or full-depth reconstruction are more feasible treatment options.

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Alternately, a 2-inch overlay can be used to improve the pavement surface and accommodate the expected traffic over the design life until more extensive rehabilitation or reconstruction can be implemented. This treatment option, however, necessitates a grade increase of the runway. Due to the extensive cracking present on the surface of the existing pavement, a 2-inch overlay treatment option carries an increased risk of reflective cracking and premature pavement failure and is not our preferred alternative recommendation. FAARFIELD results for a 2-inch overlay of Runway 14/32 are provided on Figure 2D in Appendix D.

3.3.3 Pavement Reconstruction

Our recommendations for reconstruction were controlled by the required minimum design thicknesses specified in FAA Advisory Circular 150/5320-6G. It should be noted that the minimum design thicknesses given in FAA Advisory Circular 150/5320-6G for an aircraft weight class of greater than 100,000 pounds specify the use of a stabilized base layer between the AC and AB layers. Our analysis indicates a stabilized base layer is not needed from a structural standpoint; however, we have included design alternatives for full-depth reconstruction both with and without a stabilized layer.

3.4 Pavement Design Recommendations

Our pavement design recommendations for Runway 14/32 at Cape Blanco Airport are based on the results of our structural analyses described above.

3.4.1 Pavement Partial-Depth Reconstruction

Partial-depth reconstruction involves removing the existing AC and a portion of the existing AB from Runway 14/32 and replacing it with new AC. The FAARFIELD analysis indicates that removing the upper 4 inches of existing AC and AB material from the runway and replacing it with 4 inches of Oregon Department of Transportation (ODOT) Level 3, ½-inch dense asphalt concrete pavement will provide adequate structural capacity to support the expected aircraft loading for the 20-year design life. The analysis indicates that removing the upper 3 inches of material and replacing it with 3 inches of ODOT Level 3, ½-inch dense AC pavement will provide enough structural capacity to support the expected aircraft loading for approximately 17 years. The FAARFIELD results are summarized in Table 3-4, and on Figure 3D in Appendix D.

3.4.2 Pavement Full-Depth Reconstruction

We provided recommendations for full-depth reconstruction of Runway 14/32 with and without a stabilization layer between the AC and AB layers. Pavement design recommendations for the full-depth reconstruction are provided in Table 3-4 and on Figure 4D in Appendix D.

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Table 3-4: PAVEMENT DESIGN ALTERNATIVES FOR PARTIAL- AND FULL-DEPTH RECONSTRUCTION

Design Alternative

Thickness, inches

AC (P-

401)

AC Stabilization Layer (P-403)

AB (P-

209)

Approximate Remaining Existing AB

3-Inch Thick Partial-Depth Reconstruction

3 -- -- 15¾

4-Inch Thick Partial-Depth Reconstruction

4 -- -- 14¾

Full-Depth Reconstruction with Stabilization

4 5 6 --

Full-Depth Reconstruction without Stabilization 4 -- 12½ --

Notes:

a. A 3-inch partial-depth reconstruction provides structural capacity to accommodate the expected traffic loading for approximately 17 years.

b. Existing AB represents the average existing AB thickness remaining after removing the upper 4 inches of existing material.

c. Minimum and maximum lift thicknesses for AC placement should be 2 inches and 3 inches, respectively.

d. Use ODOT Level 3, ½-inch dense asphalt concrete pavement with Performance Grade (PG) 64-22 binder.

e. We recommend placing a non-woven Class 2 geotextile between the existing soil and an AB layer.

f. Exposed subgrade material should be compacted to meet FAA requirements prior to placement of AB.

3.5 Pavement Classification Rating

We calculated the Pavement Classification rating (PCR) value for each pavement design alternative. We used FAARFIELD version 2.0.7 to compute the PCR. The results of the PCR are provided in Table 3-5 and graphs of the PCR analysis for each design alternative are provided in Figures 1E through 5E in Appendix E.

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Table 3-5: PAVEMENT CLASSIFICATION RATING RESULTS

Design Alternative PCR

2-Inch Overlay 419/F/C/X/T

3-inch Partial-Depth Reconstruction 304/F/C/X/T

4-inch Partial-Depth Reconstruction 324/F/C/X/T

Full-Depth Reconstruction with Stabilization 462/F/C/X/T

Full-Depth Reconstruction without Stabilization 314/F/C/X/T

4 CONSTRUCTION CONSIDERATIONS

4.1 General

Our design recommendations assume construction materials and methods will be based on applicable sections of the FAA Advisory Circular 150/5370-10H, Standard Specifications for Construction of Airports. The following provides a discussion of pertinent design construction considerations for the recommendations provided for Runway 14/32. Per FAA Advisory Circular 150/5370-10H, State highway specifications may be used for pavement projects at non-primary airports serving aircraft less than 60,000 pounds, in states where the state has received FAA approval. Equivalent specifications from the 2021 ODOT Oregon Standard Specifications for Construction (OSSC) are provided in Table 4-1, for each of the materials and activities discussed below.

Table 4-1: RECOMMENDED MATERIAL SPECIFICATIONS

Materials/Activity

FAA Advisory Circular

150/5370-10H

ODOT

OSSC Specification Modifications

Subgrade Preparation and Compaction

P-152

Section 00330 and

Section 00331

Subgrade Geosynthetics P-154 Section 00350

Cold Plane Pavement Removal

P-101 Section 00620

Subbase Course P-154 Section 00641

Cement-Treated Subgrade

P-156 -- --

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Materials/Activity

FAA Advisory Circular

150/5370-10H

ODOT

OSSC Specification Modifications

Crushed Aggregate Base Course

P-209 Section 00641

(¾-inch-0)

Use under AC for roadway and temporary pavement construction.

Asphalt Mix Pavement P-403 Section 00744

The minimum lift thickness is 2 inches, and the maximum lift thickness is 3 inches for dense AC.

Use ODOT Level 3, ½-inch dense ACP.

Asphalt Mix Pavement P-401 Section 00745

The minimum lift thickness is 2 inches, and the maximum lift thickness is 3 inches for dense AC.

Use ODOT Level 3, ½-inch dense ACP.

Asphalt Binder -- -- Use PG 64-22 Asphalt Cement.

4.2 Discussion of Subgrade Conditions

The subgrade underlying the project area typically consists of sand or sand with some silt.

USCS classifications for these soils include SW and SP. Appendix A of the 2021 FAA Airport Pavement Design and Evaluation Advisory Circular (FAA AC No.: 150/5320-6G) indicates that soils within this range of classifications can vary from “fair” to “good” as a foundation material. Appendix A also indicates the potential for frost action can range from none to very slight and drainage is typically excellent. Further discussion of frost considerations is provided below.

4.3 Subgrade Preparation and Parameters for New Pavement Design

4.3.1 Subgrade Preparation

Subgrade preparation should follow the requirements for Item P-152 as summarized in the current FAA Standard Specifications for Construction of Airports (FAA AC No.:

150/5370-10H). We recommend the earthwork and compaction criteria assume cohesive soils (i.e., Plasticity Index (PI) > 3) even where the subgrade is comprised of predominantly granular soils because of the prevalence of silt and clay within the subgrade.

Subgrade below existing pavements is expected to have variable composition and may include variable amounts of organic material and clay at varying depth. Compaction of the subgrade will not be practical if the soils are overly wet. Therefore, if construction during wet weather is necessary, it will likely require a thickened aggregate base, subbase course, and/or granular stabilization fill to reduce the potential for subgrade disturbance. A minimum of 18 inches to 24 inches of granular fill over a separation geotextile placed on firm subgrade is typically required to limit the risk of subgrade pumping during construction. Alternatively, cement treatment may be used following the requirements of Item P-156 (Cement-Treated Subgrade) in FAA AC No.: 150/5370-10H. For this option, a cement application rate of about 3% to 5% of the dry unit weight should be assumed. A

GRI 6706-A – Cape Blanco Airport Runway 14/32 Pavement Report Page 10 reduced subgrade design strength (i.e., lower design subgrade CBR or resilient modulus value) may also be necessary if subgrade compaction is not feasible and should be further evaluated by the project team if this option is selected.

4.4 Frost Considerations

The FAA frost group classification for the subgrade soils encountered during our explorations is FG-2 based on the classifications in FAA AC No.: 150/5320-6G Table 2-2, which indicates low to moderate frost susceptibility.

Complete mitigation of the risk of detrimental frost heave requires overexcavation and replacement of frost-susceptible soils below the depth of frost penetration. The local building code in Curry County indicates a frost penetration depth of 12 inches in the area that includes Cape Blanco Airport (referenced in Table R301.2(1) of the 2021 Oregon Residential Specialty Code (ORSC). Therefore, designing for frost mitigation is not a concern for new pavement sections thicker than 12 inches.

4.5 General Construction Considerations

4.5.1 Construction Timing

The soils underlying Runway 14/32 may be moisture sensitive. Therefore, it is our opinion earthwork can be completed most economically during the dry summer months, typically extending from July to mid-October.

4.5.2 Fill Materials and Compaction

The base aggregate for new pavements should consist of well-graded crushed gravel or rock conforming to FAA P-209 requirements. Subbase should consist of free-draining sand, gravel, rock, asphalt grindings, or mixtures of the above that conform to FAA P-154 requirements and are free of plastic clay and organic matter.

Granular stabilization fill, if required to mitigate soft and/or overly wet soil conditions, should consist of 3-inch-minus, clean (i.e., less than 5% passing the No. 200 sieve), well-graded, angular, crushed (quarry) rock. Stone Embankment Fill, as defined in the Oregon Standards Specification for Construction; Section 00330.16 (ODOT 2021), may be specified with the alteration that a maximum particle size of 3 inches is required. The gradation of the Stabilization Fill meets the requirements for Subbase Course (Item P-154) and may be substituted for subbase where overexcavation is required. The percent fractured faces for the angular material should meet the requirements for Item P-209 but may be confirmed by visual observation.

A separation geotextile placed over the finished subgrade will facilitate placement of the base materials and limit migration of fine-grained subgrade into the aggregate base or subbase for long-term protection. The separation geotextile should consist of a woven or

GRI 6706-A – Cape Blanco Airport Runway 14/32 Pavement Report Page 11 non-woven geotextile with Mean Average Roll Value (MARV) strength properties meeting the requirements of an AASHTO M 288-17 Class 2 geotextile. The geotextile should have MARV hydraulic properties meeting the requirements of AASHTO M 288-17, Table 3 with a permittivity greater than 0.05 sec.-1 and an Apparent Opening Size (AOS) less than

0.6 mm (max average roll value).

All fills should be placed in level lifts and compacted based on FAA requirements for the selected material type, as defined in FAA AC No.: 150/5370-10H. The moisture content of the fill should be adjusted to within about 2% of its optimum value prior to compaction.

Field-density tests should be run frequently to confirm adequate compaction of the aggregate base, subbase, and subgrade. Adequate compaction of fill materials, which are too coarse or too variable for density testing, should be evaluated by observation of the compaction method and proof-rolling with a loaded dump truck or other approved heavy construction vehicle.

5 DESIGN REVIEW AND CONSTRUCTION SERVICES

We welcome the opportunity to review and discuss construction plans and specifications for these projects as they are being developed. In addition, GRI should be retained to review all pavement-related portions of the plans and specifications to evaluate whether they are in conformance with the recommendations provided in our report. To maintain GRI as the engineer of record for pavement-related components of this project, a GRI representative shall be retained to observe compliance with the intent of our recommendations, the design concepts, and the plans and specifications. Our construction-phase services will allow for timely design changes if site conditions are encountered that are different from those described in our report. If we do not have the opportunity to confirm our interpretations, assumptions, and analyses during construction, we cannot be responsible for the application of our recommendations to subsurface conditions different from those described in this report.

6 LIMITATIONS

This report summarizes the results of subsurface explorations completed for the project, our pavement design analysis, and pavement design recommendations. The scope of this report is limited to the specific project and location described herein, and our description of the project represents our current understanding of the significant aspects of the proposed runway rehabilitation project. The data provided in this report were obtained from the subsurface explorations made at the locations indicated on Figure 2, and other sources of information as discussed in this report. In the performance of subsurface investigations, specific information is obtained at specific locations at specific times.

However, it is acknowledged that variations in soil conditions may exist between exploration locations, and this report does not necessarily reflect these potential variations.

GRI 6706-A – Cape Blanco Airport Runway 14/32 Pavement Report Page 12

RENEWS: 06/2023

Please contact the undersigned if you have any questions regarding this report.

Submitted for GRI, Lindsi A. Hammond, PE Matthew A. Haynes, PE Principal Project Engineer

This document has been submitted electronically.

GRI 6706-A – Cape Blanco Airport Runway 14/32 Pavement Report Page 13

7 REFERENCES

FAA, 2021, Airport pavement design and evaluation advisory circular: AC No.: 150/5320- 6G, Federal Aviation Administration.

FAA, 2018, Standards for specifying construction of airports advisory circular: AC No.:

150/5370-10H, Federal Aviation Administration.

ODOT, 2021, Oregon standard specifications for construction, Oregon Department of Transportation.

ORSC, 2021, Oregon residential specialty code (ORSC): based on 2018 International residential code (IRC), International Code Council, Inc., ISBN: 978-1-60983-736-5.

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APPENDIX A

Field Explorations and Laboratory Testing

GRI 6706-A – Cape Blanco Airport Runway 14/32 Pavement Report Page A-1

APPENDIX A

FIELD EXPLORATIONS AND LABORATORY TESTING

A.1 FIELD EXPLORATIONS

A.1.1 General Subsurface materials and conditions at the site were evaluated on August 18, 2022, with eight full-depth pavement boring explorations, designated B-1 through B-8. A GRI representative directed the subsurface exploration program and maintained a log of the materials and conditions disclosed during the course of the work.

The pavement borings were advanced to depths of about 7½ feet below ground surface with solid-stem auger techniques using a trailer-mounted drill rig provided and operated by Pacific Pole Base & Drilling, LLC, of Molalla, Oregon. Continuous disturbed soil samples were obtained from the borings using a standard split-spoon sampler. The standard penetration test (SPT) was completed while obtaining disturbed soil samples. This test is performed by driving a 2-inch-diameter, split-spoon sampler into the soil a distance of 18 inches using the force of a 140-pound hammer dropped 30 inches. The number of blows required to drive the sampler the last 12 inches is known as the Standard Penetration Resistance, or SPT N-value. The SPT N-values provide a measure of the relative density of granular soils and the relative consistency of cohesive soils. Our staff examined the soil samples in the field and saved portions in sample jars for further examination and physical testing in our laboratory.

A.1.2 Exploration Logs The approximate locations of the explorations completed for this project are shown on the Site Plan, Figure 2. A summary of pavement core thickness and condition from each boring is provided on Figure 1A. Logs of the borings are provided on Figures 2A through 9A. Each log presents a descriptive summary of the various types of materials encountered in the boring and notes the approximate depth where the materials and/or characteristics of the materials change. To the right of the descriptive summary, the numbers and types of samples that were taken during the drilling operation are indicated. Farther to the right, field-measured blow counts and moisture contents are shown graphically. Photographs of the pavement cores retained from our pavement boring explorations are shown on Figures 10A through 17A. Using the terms and symbols defined in Table 1A, a summary of our observations from the explorations is presented in Table 2A.

GRI 6706-A – Cape Blanco Airport Runway 14/32 Pavement Report Page A-2

A.1.3 Dynamic Cone Penetrometer Tests During the boring explorations, GRI completed eight dynamic cone penetrometer (DCP) test probes (B-1 DCP through B-8 DCP). We advanced the DCP test probes to depths ranging from about 21 inches to about 33 inches into the aggregate base and subgrade soils below the AC.

We used our Kessler DCP manufactured by KSE Testing Equipment to complete the tests in general accordance with ASTM International (ASTM) D6951 by driving a ⅝-inch-diameter steel rod with a cone tip into the soil using a 17.6-pound sliding hammer dropped a fixed height of 22.6 inches. We recorded the number of hammer drops (blows) required to drive the probe in increments of approximately 2 inches or the penetration depth for each blow in soft subgrade soils.

Using the recorded test data, we plotted cumulative blows against cumulative penetration depths and visually assessed the resulting curve to delineate regions with approximately linear slopes. We then used least square regression to calculate the slope of the approximately linear regions along the curve and used the procedures described by Chen et al. (1999) to approximate the resilient modulus for each region. Where a curve exhibited more than one slope within the subgrade layers, we used Odemark’s Method of Equivalent Thickness described by Ullidtz (1998) to calculate an equivalent modulus value for the entire data set of similar soil types.

Cumulative blows versus cumulative penetration depths are listed and presented graphically on Figures 18A through 25A in this appendix. Also shown on the figures are the approximated resilient modulus values and the equivalent modulus value if the data exhibits more than one approximately linear region for a given soil type.

A.2 LABORATORY TESTING

A.2.1 General The samples obtained from the full-depth pavement borings were examined in our laboratory, where the physical characteristics of the samples were noted, and the field classifications were modified where necessary. At the time of classification, the natural moisture content of each sample was determined. Additional testing included grain-size analysis on select soil samples.

The following sections describe the typical laboratory testing program in more detail.

A.2.2 Natural Moisture Contents Natural moisture content determinations were made in conformance with ASTM International (ASTM) D2216. The results are summarized in Table 2A and on Figures 2A through 9A.

GRI 6706-A – Cape Blanco Airport Runway 14/32 Pavement Report Page A-3

A.2.3 Grain-Size Analysis To assist in classification of the soils, select samples with known dry weight were washed over a No. 200 sieve. The material retained on the sieve was oven-dried and weighed. The percentage of material passing the No. 200 sieve was then calculated. The results are summarized on Figures 2A, 4A, 6A, and 8A, and in Table 2A.

Table 1A

GUIDELINES FOR CLASSIFICATION OF SOIL

Description of Relative Density for Granular Soil

Relative Density Standard Penetration Resistance

(N-values) blows/ft

Very Loose 0 - 4

Loose 4 - 10

Medium Dense 10 - 30

Dense 30 - 50

Very Dense over 50

Description of Consistency for Fine-Grained (Cohesive) Soils

Consistency

Standard Penetration Resistance (N-values) blows/ft

Torvane or Undrained Shear

Strength, tsf

Very Soft 0 - 2 less than 0.125

Soft 2 - 4 0.125 - 0.25

Medium Stiff 4 - 8 0.25 - 0.50

Stiff 8 - 15 0.50 - 1.0

Very Stiff 15 - 30 1.0 - 2.0

Hard over 30 over 2.0

Description of Consistency for Coarse-Grained (Non-Cohesive) Soils

Grain-Size Classification Modifier for Subclassification

Boulders:

>12 in.

Cobbles:

3-12 in.

Gravel:

¼ - ¾ in. (fine) ¾ - 3 in. (coarse) Sand:

No. 200 - No. 40 sieve (fine) No. 40 - No. 10 sieve (medium) No. 10 - No. 4 sieve (coarse) Silt/Clay:

Pass No. 200 sieve

Adjective

Primary Constituent SAND or GRAVEL

Primary Constituent SILT or CLAY

Percentage of Other Material (By Weight) trace: 5 - 15 (sand, gravel) 5 - 15 (sand, gravel) some: 15 - 30 (sand, gravel) 15 - 30 (sand, gravel) sandy, gravelly: 30 - 50 (sand, gravel) 30 - 50 (sand, gravel) trace: <5 (silt, clay) Relationship of clay and silt determined by plasticity index test some: 5 - 12 (silt, clay) silty, clayey: 12 - 50 (silt, clay)

0.0

1.0

2.0

3.0

4.0

11+06 18+07 25+84 30+56 39+98 45+96 53+67 59+83

7 feet East 7 feet West 40 feet East 7 feet East 7 feet West 7 feet West 40 feet East 7 feet West B-1 B-2 B-3 B-4 B-5 B-6 B-7 B-8

Y axis = Depth, inches | X Axis = Core No. / Test Line / Approximate Station

Good AC Fair AC Delamination and Stripping Delamination Crack

CORE SUMMARY CHART

Runway 14/32

JAN. 2023 JOB NO. 6706-A FIG. 1A

Note: Test Line indicates distance from Runway 14/32 centerline

GRAVEL; clean to some silt, clay, and sand

Sandy GRAVEL; clean to some silt and clay

Silty GRAVEL; up to some clay and sand

Clayey SAND; up to some silt and gravel

Gravelly CLAY; up to some silt and sand

Sandy CLAY; up to some silt and gravel

Silty CLAY; up to some sand and gravel

Symbol Description

Flush-mount monument set in concrete

Concrete, well casing shown where applicable

Filter pack, machine-slotted well casing shown where applicable

1-in.-diameter solid PVC

FIELD MEASUREMENTS

Typical Description

Groundwater level after drilling and date measured

Symbol Typical Description

BASALT

MUDSTONE

SILTSTONE

PEAT

Symbol

FILL

Clayey GRAVEL; up to some silt and sand

SAND; clean to some silt, clay, and gravel

SILT; up to some clay, sand, and gravel

Gravelly SILT; up to some clay and sand

Sandy SILT; up to some clay and gravel

Clayey SILT; up to some sand and gravel

CLAY; up to some silt, sand, and gravel

Grab Sample

Rock core sample interval

Sonic core sample interval

INSTALLATION SYMBOLS

Symbol

Bentonite seal, well casing shown if applicable

Vibrating-wire pressure transducer

SymbolBEDROCK SYMBOLS

SOIL SYMBOLS

Typical Description

SAMPLER SYMBOLS

Sampler DescriptionSymbol

LANDSCAPE MATERIALS

Gravelly SAND; clean to some silt and clay

Silty SAND; up to some clay and gravel

Shelby tube sampler with recovery

(ASTM D1587)

Grout, vibrating-wire transducer cable shown where applicable

1-in.-diameter hand-slotted PVC

Grout, inclinometer casing shown where applicable

Groundwater level during drilling and date measured

SANDSTONE

SURFACE MATERIAL SYMBOLS

Symbol Typical Description

BORING AND TEST PIT LOG LEGEND

Rock quality designation (RQD, %)

Asphalt concrete PAVEMENT

Portland cement concrete PAVEMENT

Crushed rock BASE COURSE

2.0 in. O.D. split-spoon sampler and Standard Penetration Test with recovery (ASTM D1586)

3.0 in. O.D. split-spoon sampler with recovery

(ASTM D3550)

Push probe sample interval

Rock/sonic core or push probe recovery (%)

B O

R

IN

G A

N D

T E

S T

P

IT

L O

G L

E G

E N

D G

R I D

A T

A T

E M

P

LA

T E

.G D

T

/7 /2

JAN. 2023

BORING LOCATION AND

PAVEMENT CORE PHOTOGRAPHS

JAN. 2023 JOB NO. 6706-A FIG. 10A

Boring B-1 Location

Core B-1 Sample

JAN. 2023 JOB NO. 6706-A FIG. 11A

Boring B-2 Location

Core B-2 Sample

JAN. 2023 JOB NO. 6706-A FIG. 12A

Boring B-3 Location

Core B-3 Sample

JAN. 2023 JOB NO. 6706-A FIG. 13A

Boring B-4 Location

Core B-4 Sample

JAN. 2023 JOB NO. 6706-A FIG. 14A

Boring B-5 Location

Core B-5 Sample

JAN. 2023 JOB NO. 6706-A FIG. 15A

Boring B-6 Location

Core B-6 Sample

JAN. 2023 JOB NO. 6706-A FIG. 16A

Boring B-7 Location

Core B-7 Sample

JAN. 2023 JOB NO. 6706-A FIG. 17A

Boring B-8 Location

Core B-8 Sample

APPENDIX B

Falling Weight Deflectometer Test Results

GRI 6706-A – Cape Blanco Airport Runway 14/32 Pavement Report Page B-1

APPENDIX B

FALLING WEIGHT DEFLECTOMETER TEST RESULTS

B.1 GENERAL

GRI conducted falling weight deflectometer (FWD) deflection tests within the project limits on August 17, 2022, using our KUAB 2m Model 150 FWD, which generally complies with ASTM D4694. We conducted FWD testing at approximately 200-foot intervals along four test lines on Runway 14/32. Additional details are provided below.

B.2 TEST PROCEDURE

The FWD test sequence consisted of applying a seating impact load followed by recording the surface deflections generated by two impact loads at nominally 32,000 pounds each.

The FWD load is generated by a two-mass/two-buffer falling-weight system that produces a nearly haversine-shaped, load-pulse waveform. The buffer and weight combination used for these tests produces a load rise time of approximately 14 milliseconds with an equivalent haversine frequency of approximately 32 Hertz. The FWD applies the load pulse to the pavement surface through a 450-millimeter-diameter (8.86-inch-radius), four-part, segmented plate designed to apply uniform surface-pressure distribution despite irregularities in the pavement surface. The FWD measures pavement-surface deflections using seismometers (absolute deflection sensors) positioned, with respect to the center of the load plate, at distances of 0 inches, 12 inches, 18 inches, 24 inches, 36 inches, 48 inches, 60 inches, and 72 inches. The FWD also records air temperature and pavement-surface temperature (the latter measured by infrared thermometer) for each test.

B.3 TEST DATA

B.3.1 General We linearly normalized the deflections generated by each applied load to a 30-kip (30,000-pound) load and calculated the average value at each sensor location. The normalized deflections, mid-depth AC temperature, and deflection under the load plate (D0) at each FWD test location conducted are listed in Table 1B of this appendix. The measurement units for the test data are distance in feet, deflections in mil units (1 mil = 0.001 inch), load in pounds, sensor distance in inches, load-plate radius in inches, and temperature in degrees Fahrenheit.

B.3.2 Impulse Stiffness Modulus (ISM) The Impulse Stiffness Modulus (ISM) shown in units of kips per inch is the composite stiffness, or dynamic plate bearing modulus, of all the materials beneath the pavement

GRI 6706-A – Cape Blanco Airport Runway 14/32 Pavement Report Page B-2 surface. It is computed using the Boussinesq formula for surface deflection beneath the center of a uniformly loaded circular area on a linear-elastic half space, with a Poisson’s ratio of 0.40.