Pavements Report_CA ERFO FS LSPDR 2023-1(1B) Black Mountain Rd.pdf

PAVEMENT REPORT

CA ERFO FS LSPDR 2023-1(1B)

Black Mountain Road

Los Padres National Forest, San Luis Obispo County, CA

Yeh Project No.: 222-381C

August 27, 2025

Prepared for:

Jacobs 6312 South Fiddlers Green Circle, Suite 300N

Greenwood Village, CO 80111 Attn: James Mills, P.E.

Prepared by:

Yeh and Associates, Inc.

391 Front Street, Suite D

Grover Beach, California 93433 Phone: 805-481-9590

391 Front Street, Suite D Grover Beach, CA 93433

(805) 481-9590 www.yeh-eng.com

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PAVEMENT REPORT

CA ERFO FS LSPDR 2023-1(1B)

Black Mountain Road

Los Padres National Forest, San Luis Obispo County, CA

Yeh Project No.: 222-381C

August 27, 2025

Prepared by:

Jason Frame, E.I.T. (CA) Staff Engineer

Independent Reviewer:

Judd King, P.E. (CA, AZ), G.E. (CA) Senior Geotechnical Engineer http://www.yeh-eng.com/ Judd King JJK GE Stamp

Pavement Report Yeh Project No. 222-381C Black Mountain Road – CA ERFO FS LSPDR 2023-1(1B) August 27, 2025 i

TABLE OF CONTENTS

1. PURPOSE AND SCOPE OF STUDY

2. PROJECT UNDERSTANDING

3. EXISTING CONDITIONS

4. GEOTECHNICAL EXPLORATION AND TESTING

4.1 EXPLORATORY DRILLING

4.2 LABORATORY TESTING

5. SITE CONDITIONS

5.1 TERRAIN AND VEGETATION

5.2 CLIMATE

5.3 EXISTING ROADWAY AND SURFACE PAVEMENT CONDITIONS

6. PAVEMENT AND SUBGRADE CONDITIONS

7. CONCLUSIONS AND RECOMMENDATIONS

7.1 EARTHWORK FACTORS

7.2 SUBEXCAVATION

7.3 PAVEMENT DESIGN RECOMMENDATIONS

7.3.1 SUBGRADE

7.3.2 DESIGN TRAFFIC VOLUME

7.3.3 STRUCTURAL SECTION

7.3.4 BINDER AND MIX RECOMMENDATIONS

7.3.5 PAVEMENT MAINTENANCE

7.4 CORROSION CONSIDERATIONS

7.5 SLOPE REPAIR AT STATION 144+00

8. CONSTRUCTION CONSIDERATIONS

8.1 EXCAVATION CONSIDERATIONS

8.2 MATERIAL SOURCES

8.2.1 CONCRETE, ASPHALT CONCRETE AND AGGREGATE

8.2.2 GENERAL BORROW

9. LIMITATIONS

10. REFERENCES

ii

List of Figures

FIGURE 1: PROJECT LOCATION MAP

FIGURE 2: TYPICAL PAVEMENT DISTRESS

List of Tables

TABLE 1: EXISTING PAVEMENT CONDITIONS ENCOUNTERED

TABLE 2: SUBGRADE LABORATORY TEST SUMMARY

TABLE 3: ESTIMATED SHRINKAGE FACTORS

List of Plates

Boring Location Map

List of Appendices

Page Appendix A – Boring Logs

Legend for Soil Classification .................................................................................................................. A-1 Boring Logs for 25P-01 to 25P-07 ................................................................................................... A-2 to 8 Drill Rig Set Up Photos .................................................................................................................. A-9 to 10

Appendix B – Results of Laboratory Testing Summary of Laboratory Results ............................................................................................................. B-1 Sieve Analysis ......................................................................................................................................... B-2 Corrosivity Tests Summary ..................................................................................................................... B-3 Proctor Compaction ............................................................................................................................... B-4 R-Value ............................................................................................................................................ B-5 to 7

Appendix C – Pavement Patching Areas Table ................................................................................................................................................ C-1 to 2

Appendix D – Pavement Design Calculations AASHTO Pavement Design Calculations .......................................................................................... D-1 to 2

1. PURPOSE AND SCOPE OF STUDY

Yeh and Associates was retained by Jacobs to provide pavement design recommendations for the design of the Federal Highway Administration, Central Federal Lands Highway Division (FHWA- CFLHD) Black Mountain Road project in Los Padres National Forest, California. The project is located on a 7-mile-segment of Navajo Road (Forest Service ‐ FS Route 29S02) and Black Mountain Road (FS Route 29S10) in Los Padres National Forest, California. The site location is shown on Figure 1.

The geotechnical evaluation consisted of a program of project coordination, field exploration, data review, laboratory testing, and engineering analyses as a basis for providing the recommendations in this report. This report provides recommendations and geotechnical considerations for earthwork, pavement design, corrosion, construction, and material sources.

2. PROJECT UNDERSTANDING

The project generally consists of the rehabilitation of an approximately 7-mile segment of the Navajo and Black Mountain Roads. The route is referred to as Black Mountain Road for the purposes of this project. The project limits extend from Milepost 0.297 of Navajo Road (Station 100+00) and continues for approximately 3.1 miles where Black Mountain Road connects and heads up to an FAA radar facility located an additional 3.9 miles up the road (Station 463+00) (Jacobs 2025). The proposed improvements along Black Mountain Road generally include new structural roadway sections for Black Mountain Road and drainage/culvert repairs and/or replacements. One contractor designed mechanically stabilized earth wall is also planned at Station 144+00 to 144+40 where the downhill side of the road has failed.

3. EXISTING CONDITIONS

The project site is located in Los Padres National Forest approximately 15 miles east of Santa Margarita, California with elevations along the roadway ranging from approximately elevation 1,850

Figure 1: Project Location Map to 3,570 feet and with grades along the roadway ranging from approximately 0 to 22 percent (CalTopo 2023). Black Mountain Road is a side‐hill, cut and fill, single‐lane road that was constructed over 50 years ago to provide access to the FAA radar facility located on the mountain top at the end of the road. The majority of road benches were made in cut; however, a layer of side‐cast fill is commonly present within the outer 3 to 6 feet of the roadbed that overlies the downhill side of the road. The side‐cast fill appears to be poorly compacted and was likely made without keying and benching into the hillside below the fill. Upslope cuts are up to approximately 60 feet high with inclinations that vary from 45 to 75 degrees.

The fill slopes on the downslope side of the road are estimated to range from approximately 4 to 30 feet high within the locations that we assessed. Fill slopes and failures descend off the roadway at inclinations of 40 to 45 degrees. The road is paved with asphalt concrete, has a typical paved width of 11 to 13 feet, a 1‐ to 4‐foot‐wide outside shoulder along the downhill side of the road, and 0.5‐ to 4‐ foot‐wide ditches along the base of the cuts. Overside drains are provided by corrugated metal open channel drainage flumes. Surface water is directed to drainage flumes with transverse asphalt mounds constructed in the roadway and earth berms constructed along the roadway shoulder

The road became unsafe after heavy rains impacted the road and caused embankment slope failures in the winter of 2022/2023. Damaged sections were repaired in the summer of 2024 using mechanically stabilized earth walls and replacement of drainage flumes. Jacobs (2023) and Yeh (2023) provided plans and specifications for an emergency reopening project. New pavement sections consisting of 3 inches of HMA over 6 inches of aggregate base were constructed at these locations.

An additional slope failure at approximately Station 144+00 to 144+40 was noted during the 30 percent design review held on April 29-30, 2025. The travel width in this location has been reduced from 13 feet to 10.5 feet with a nearly vertical eroded slope and a drainage flume detached from the road and washed down the fill slope. The slope failure has a 6-to-8-foot scarp immediately adjacent to the roadway. The failure appears to be similar to the slope failures repaired in 2024 which required the design and construction of MSE walls with new drainage flumes. A contractor-designed MSE wall was selected by CFL to restore the roadway width at this location and repair the drainage flume.

4. GEOTECHNICAL EXPLORATION AND TESTING

Geotechnical exploration consisted of a program of exploratory drilling and laboratory testing. The locations of the borings are shown on Plate 1. The boring logs are presented in Appendix A.

Laboratory test results are presented in Appendix B.

4.1 EXPLORATORY DRILLING

The drilling subcontractor for this project was Bryer Carlson Drilling Contractor (BCDC) of Morro Bay, California. BCDC drilled a total of seven borings on June 6, 2025. The borings were drilled using a truck-mounted CME-55 drill rig equipped with 8-inch hollow stem augers. The borings were drilled to depths up to 6.5 feet below the ground surface. Yeh personnel logged the subgrade conditions encountered and secured samples for subsequent laboratory testing. All holes were backfilled with the native soil and topped with rapid set concrete dyed black.

Sampling within the borings was performed by driving either a modified California or standard penetration test (SPT) split spoon sampler at depths of 1-foot and 5-feet. Bulk samples were also collected from the auger flights within the upper 5 feet of the boring. The SPT sampler has a 2-inch outside diameter, 1-3/8-inch inside diameter and is equipped for but was used without liners. The modified California sampler has a 3-inch outside diameter, 2-3/8-inch inside diameter and was used with 1-inch-high brass liners. The drive samples were collected using a 140-pound manual donut hammer using a cathead hoist in accordance with ASTM D1586, Standard Penetration Test, procedures. The sampling depth, selected lab test results, recorded blow counts (N-values) for the driven samples, and a description of subsurface conditions encountered are presented on the boring logs in Appendix A.

4.2 LABORATORY TESTING

The results of laboratory tests are presented in Appendix B. Laboratory tests were performed on selected samples recovered from the field exploration program. Tests for moisture content, unit weight, sieve analysis, percent passing the 200 sieve, Proctor Compaction, and pH and resistivity were performed at our laboratory in Grover Beach, California. Tests for soluble sulfates and soluble chlorides as well as R-Value were performed by Cooper Testing Labs in Palo Alto, California. Testing was performed in accordance with American Society for Testing and Materials (ASTM) and American Association of State Highway and Transportation Officials (AASHTO) methods as noted on the lab reports. After the completion of the laboratory testing, the field descriptions were confirmed or modified as necessary and boring logs were completed.

5. SITE CONDITIONS

5.1 TERRAIN AND VEGETATION

The project site is located on a windy west facing slope, approximately 15 miles east of Santa Margarita, California, within the Central Coast Range foothills. The Black Mountain Road project site begins at the Turkey Flat recreational OHV staging area used year-round. Elevations along Black Mountain Road vary between approximately 1800 and 3500 feet (Google Earth 2025). Vegetation is sparse at the highest points along the ridge and includes thicker vegetation of trees and shrubbery at lower elevations.

5.2 CLIMATE

The local climate is characterized by moderately hot, dry summers and moderately cool, low precipitation winters. Climate data from World Weather Online (WWO 2025) for Santa Margarita, CA, reports an average annual rainfall of about 15 inches. Most of the rainfall is reported to occur during the winter months between November and March. Monthly average temperatures range from a low of 45 degrees Fahrenheit in December to February and a high of 83 degrees Fahrenheit in August (WWO 2025).

5.3 EXISTING ROADWAY AND SURFACE PAVEMENT CONDITIONS

Black Mountain Road is a single-lane road with asphalt pavement and an average paved width of approximately 12 feet (Jacobs 2025). The road provides access to recreational day use areas, multiple communications towers, and an FAA radar facility. The road includes several drainage flumes some of which require maintenance and/or replacement. Extensive portions of the roadway are in poor condition with areas of intense fatigue cracking, block cracking, edge cracking, and potholes. High severity fatigue (left photo) and block cracking with complete erosion of the pavement surface at some points (right photo) are shown in Figure 2. Yeh catalogued recommended patch areas during the April 29-30, 2025 site visit. Pavement areas were measured and graded as low, medium and high severity. Those data are included in Appendix C.

6. PAVEMENT AND SUBGRADE CONDITIONS

The approximate boring locations are shown on Plate 1. Logs of the borings and photographs of the drill rig are included in Appendix A. The existing structural section encountered in the borings

Figure 2: Typical Pavement Distress generally consisted of 2 to 4 inches of asphalt concrete (AC) with no aggregate base (AB). Pavement was generally placed over subgrade soil. The pavement thicknesses encountered in each boring are shown in Table 1 below. The subgrade conditions encountered below the pavement generally consisted of medium dense to very dense clayey sand (SC) and dense to very dense well-graded sand with varying amounts of clay (SW-SC). R-Values of 16 and 78 were obtained from tests performed on samples of the subgrade. The dry unit weights of the subgrade samples vary from 102 to 118 pounds per cubic foot and the moisture contents vary from 2 to 10 percent. A summary of the existing structural section thickness encountered is presented on Table 1. A summary of the laboratory test results for the subgrade samples is presented in Table 2. Areas indicating subgrade distress were generally not observed.

Table 1: Existing Pavement Conditions Encountered

Boring No. Station

Asphalt Thickness (inches)1

Base Thickness (inches)

Subgrade AASHTO1 Comment

25P-01 106+10 2.0 0 Well-Graded SAND with CLAY (SW-SC) A-2 West Center

25P-02 144+40 4.0 0 CLAYEY SAND (SC)

A-3 Center

25P-03 198+00 4.0 0 CLAYEY SAND (SC)

A-4 Center

25P-04 267+30 1.0 0 Well-Graded SAND with CLAY (SW-SC) A-5 East Center

25P-05 361+50 3.0 0 CLAYEY SAND (SC)

A-6 Center

25P-06 424+50 2.5 0 CLAYEY SAND (SC)

A-7 Center

25P-07 454+10 2.5 0 CLAYEY SAND (SC)

A-8 West Center

1. Borings 25P-02 and 25P-03 drilled in patch areas and asphalt concrete thickness not necessarily indicative of the majority of the roadway.

Table 2: Subgrade Laboratory Test Summary2

Geologic Unit Dry Unit Wt.

Particle Size

Analyses Atterberg

Limits Proctor Results R-value

Asphalt Cuttings N/A N/A N/A N/A 78

1 AASHTO symbol may be based on manual classification of soil.

2 Geotechnical properties are noted for dry unit weight (γd) and moisture content (wo); particle size as percent gravel (G), sand sizes (S) and fines content (F); Atterberg limits for liquid limit (LL) and plasticity index (PI); maximum dry unit weight (γd,MAX) and optimum moisture content (wOPT).

Geologic Unit Dry Unit Wt.

Particle Size

Analyses Atterberg

Limits Proctor Results R-value

Quaternary Alluvium

(Qa) γd =111-118 pcf wo = 2-6%

0-2% G 82-89% S 9-18% F

N/A γd,MAX. = 126 pcf

WOPT. = 8%

Decomposed Granite

(Gr) γd =102-117 pcf wo = 6-10%

0-2% G 52-88% S 11-46% F

N/A γd,MAX. = 126-

127pcf

WOPT. = 8-9%

7. CONCLUSIONS AND RECOMMENDATIONS

The recommendations of this report are for use with the FHWA Standard Specifications FP-24 where Standard Specifications are referenced. Compliance with those specifications is needed for the recommendations in this report to remain applicable.

7.1 EARTHWORK FACTORS

The subgrade generally consisted of medium dense to very dense clayey sand and dense to very dense well-graded sand with clay. Drive samples had dry unit weights that ranged from approximately 102 to 118 pounds per cubic foot. The maximum dry unit weight of the subgrade estimated from Proctor tests was approximately 126 pounds per cubic foot.

It is recognized that disturbance to drive samples occurs due to compaction of samples during driving, loosening of the soil when recovering the sampler from the boring and during trimming in the laboratory. Differences in the in-situ soil density likely occur in areas where the existing pavement subgrade and embankment fill materials were compacted as opposed to where the roadway was constructed in surficial sediments.

Estimated earthwork factors for onsite material are presented in Table 3 for recommended relative compaction values. The estimated earthwork factors3 do not account for losses for removal of vegetation or unsuitable material. The earthwork factors are approximate and based on limited number of tests and may vary based on conditions encountered during construction. Pulverization of the existing pavement for full depth reclamation (FDR) typically results in an earthwork factor of 1.1 (approximately 10% swell) from the in-place existing pavement to the compacted FDR material.

3 The earthwork factor represents the ratio of the existing in-situ unit weight of the soil before construction to the unit weight of the same soil after compaction. For example, an earthwork factor of 0.95 represents a 5 percent loss in the volume of soil following compaction. An earthwork factor of 1.05 represents a 5 percent gain in volume of the soil or pavement following compaction due to bulking of a relatively dense material.

Table 3: Estimated Shrinkage Factors

Relative Compaction Estimated Shrinkage

Factor

90% 0.99

95% 0.94

7.2 SUBEXCAVATION

Depending on the time of year and moisture condition of subgrade soil, subgrade stabilization may be needed in areas where unsuitable, wet, or soft subgrade conditions are encountered during construction that will not allow for proper compaction of the subgrade or roadway base materials.

Subexcavation should be performed in accordance with CFL Standard Plan C204-51 and FP-24 Section

204.07 for areas where unstable conditions are encountered during construction. While we did not observe areas where subexcavation was needed, there might be conditions encountered during construction. Contract documents should provide for an option to provide subexcavation at the discretion of the Contracting Officer.

7.3 PAVEMENT DESIGN RECOMMENDATIONS

Pavement areas were documented and areas with low, medium and high severity were catalogued during the April 29-30, 2025 site visit. FHWA and FAA had initially planned a patching and pavement preservation method to restore the roadway. A scrub seal (chip seal with a high rejuvenating asphalt emulsion) would be applied over areas with less severe cracking and distress and over the patched areas documented in April 2025. This option (Option 3 in preliminary planning) would provide temporary surface restoration and likely need additional treatment and rehabilitation within 5 to 9 years. Additional funding was allocated and a more robust and longer life-span method of Full-Depth Reclamation (FDR) with HMA overlay was selected as the preferred option after our site visit and assessment.

The new structural section for design of the Black Mountain Road improvements was estimated based on Chapter 11 of the FHWA (2018) Federal Lands Highway Project Development and Design Manual (PDDM), the AASHTO (1993) Guide for the Design of Pavement Structures, traffic loads were estimated based on the road’s usage, and the subgrade conditions encountered. The new structural section should consist of hot mix asphalt concrete pavement (HMA) over full depth reclamation (FDR) material as recommended in the Preliminary Pavement Recommendations (Yeh 2025) memorandum.

The spreadsheet calculations for our recommended structural section, traffic loading and thickness recommendations are presented in Appendix D.

7.3.1 SUBGRADE

The subgrade encountered along the Black Mountain Road was predominantly classified as clayey sand (A-2 and A-7) and is generally considered fair to moderate support for the roadway. R-value testing was performed on two subgrade samples which resulted in 16 and 78 for two clayey sand samples. The lower result appears to be skewed due to mechanical weathering of the clayey sand (decomposed granite). An R-value of 45 was selected for design based on the subgrade materials. The recommended structural section thicknesses were estimated considering a resilient modulus (Mr) of 25,975 psi corresponding to the R-value of 45.

7.3.2 DESIGN TRAFFIC VOLUME

The design traffic volume was estimated (using traffic information provided in the Scoping Report (FHWA 2024)) and procedures in the PDDM (FHWA 2018). Average daily traffic (ADT) for current conditions (ADT < 500 vehicles per day) was considered for 1-percent growth conditions. A mix of 38-percent passenger cars (Class 2), 56-percent pickup trucks/vans (Class 3), 1 percent 3-axle trucks (Class 6), and 5 percent 2-axle tricks (Class 5) was used for design. A design life of 20 years was used in estimating the proposed structural sections for a 3R type project. The structural number needed for the pavement design was estimated to be 1.12 and is based on the subgrade conditions encountered and an estimated 50,000 equivalent single axle loads (ESALs) which is the minimum design per the PDDM.

7.3.3 STRUCTURAL SECTION

The recommended structural section for road rehabilitation is to provide a surface course consisting of a minimum of 2 inches of hot mix asphalt (HMA) pavement over a base course consisting of a minimum 4 inches of full depth reclamation (FDR per FP-24 Section 304). Pulverization for FDR can incorporate existing asphalt pavement and existing subgrade material. Note that areas paved in 2024 as part of the emergency repair project (Jacobs 2023) that are in good condition would not require FDR and HMA overlay.

Pulverizing should extend to a depth of at least 4 inches below the surface of the existing pavement.

The FDR material may then be harvested, windrowed, and regraded as-needed to provide material for reshaping the road cross section, widening, or grade adjustments (if needed). The final grading should provide at least 4 inches of compacted FDR material for the structural section prior to placing the HMA surface course. Imported Aggregate Base Course material can be added to supplement the FDR if needed and depending on the final quantity of base course material needed for design. It should be anticipated that the FDR and any supplemental base course material will need to be compacted in a maximum 6-inch lift to achieve compaction. The FDR material should be moisture conditioned and compacted to at least 95 percent relative compaction in accordance with FP-24.

Subgrade below areas outside the existing pavement areas that will be paved (such as roadside parking areas) should be prepared in accordance with FP-24 Specifications.

7.3.4 BINDER AND MIX RECOMMENDATIONS

The State of California (Caltrans 2023) has adopted a program of Asphalt Binder Grade Selection. The climate at the project site classifies as an Inland Valley Region. The recommended binder for this climate based on the Caltrans data is PG 64-10 for typical dense graded asphalt pavements.

7.3.5 PAVEMENT MAINTENANCE

The pavement condition should be periodically reviewed to evaluate the need for maintenance and rehabilitation following the initial construction and during the life of the pavement. Maintenance of asphalt concrete pavements should typically include periodic fog, chip, or slurry seals to reduce the potential for weathering, as well as overlaying with additional HMA when needed to strengthen and further the life of the pavement. Deflection surveys can be performed to evaluate the structural capacity of pavements and the need for future overlays.

7.4 CORROSION CONSIDERATIONS

Drainage structures should be designed with consideration for corrosion. The AASHTO (2024) Bridge Design Specifications define potentially corrosive soil and water conditions as the following:

• pH is less than 5.5,

• Resistivity is less than 2,000-ohm-cm,

• The soluble sulfate concentration exceeds 1,000 parts-per-million (ppm) for soil or exceeds

500 ppm for water,

• The soluble chloride concentrations exceed 500 ppm for water.

• Soils with resistivity greater than 5,000 ohm-cm are considered non-aggressive towards concrete and steel.

Tests for pH, electrical resistivity, as well as water soluble chlorides and sulfates were performed on four selected samples from the field exploration program. The test results are presented in Appendix B. The pH for the samples tested ranged from 5.83 to 6.86 and the soil resistivity ranged from 25 to 8,112 ohm-centimeters. The water-soluble chloride content for the samples tested were <2 to 48 ppm. The water-soluble sulfate content for the samples tested was 27 to 111 ppm. The samples tested are considered corrosive towards concrete and steel based on AASHTO (2024) standards;

specifically the sample from Boring 25P-01 which was located in the alluvium. Preventative measures to reduce the potential for corrosion and account for metal losses that may need to be considered for ferrous metal materials such as spillway inlet assemblies.

7.5 SLOPE REPAIR AT STATION 144+00

An MSE retaining wall is recommended to establish a minimum paved width of 13 feet and at least a 1‐foot‐wide dirt outside shoulder above the failed embankment between approximate stations 144+00 to 144+40. A contractor designed welded‐wire mechanically stabilized earth (MSE) retaining walls (per CFL Standard Drawing C257‐50) to stabilize the road at this location was selected by CFL as the preferred delivery method. This same approach was used in 2024 to repair several areas along the roadway (Yeh 2023); however, the vertical spacing of the reinforcing mats can be adjusted to 24 inches instead of 18 inches. Surficial soils sampled from the site can be considered suitable for reuse as Select Granular Backfill per FP-24 Section 704.03.

Yeh estimated the approximate wall height needed for design at this location based on existing site geometry and preferred roadway width. The wall should be approximately 40 feet long, have a minimum height of 9 feet and a minimum embedment of 2 feet below the adjacent ground surface in front of the wall. A 2-foot minimum wide bench should be provided in front of the wall. All other details should meet the requirements of CFL Standard Drawing C257‐50 and FP-24.

8. CONSTRUCTION CONSIDERATIONS

8.1 EXCAVATION CONSIDERATIONS

The existing embankment fill was likely derived from local soil and rock material taken from the nearby hillsides and road cuts where similar materials were observed. Excavation for culverts that will extend below the roadway will likely encounter bedrock, cobbles, and boulders derived from these local rocks. These materials can likely be excavated with conventional heavy construction equipment such as excavators equipped with carbide teeth and hoe rams for breaking boulders or zone of hard rock that may interfere with culvert or MSE wall excavations. Blasting for rock excavation is not anticipated for this project.

8.2 MATERIAL SOURCES

8.2.1 CONCRETE, ASPHALT CONCRETE AND AGGREGATE

The main material requirements for this project are likely to include asphalt concrete and aggregates that are available from commercial suppliers in the vicinity of Santa Margarita, California such as CalPortland, Sierra Pacific, and Martin Marietta. Haul times to the site from commercially available supplier yards should not exceed 1 hour. This report is not a statement that these potential suppliers or proposed borrow sources are pre-approved nor implies that the plants will meet quality control and material compliance for the project or materials to be placed at the site.

8.2.2 GENERAL BORROW

General borrow may be needed for trench backfill above the pipe zone for culverts, and as embankment fill if needed for grade corrections and widening. Sandy excavated onsite soil and excess material from the project area should be suitable for reuse as general borrow. Excavated onsite soil and rock may contain large particles that will need to be broken down or segregated from the fill to make the material suitable for compaction. Control of moisture content, compaction layer thickness, and selecting suitable equipment will be necessary to achieve the relative compaction for compacted fill.

9. LIMITATIONS

This study has been conducted in general accordance with currently accepted geotechnical practices in this area for use by the client for design purposes. The conclusions and recommendations submitted in this report are based upon the data obtained from drilling and sampling and our understanding of the proposed project and type of construction described in this report. If there are any changes in the project or site conditions, Yeh should review those changes and provide additional recommendations, if needed. Any modifications to the recommendations of this report or approval of changes made to the project should not be considered valid unless they are made in writing. The report and drawings contained in this report are intended for design-input; and are not intended to act as construction drawings or specifications.

Site conditions will vary between points of observation or sampling, seasonally, and with time. The nature and extent of subsurface variations across the site may not become evident until excavation is performed. If during construction, fill, soil, or water conditions appear to be different from those described herein, Yeh should be advised and provided the opportunity to evaluate those conditions and provide additional recommendations, if necessary. The geotechnical professional should observe portions of the construction and site conditions, such as excavations, exposed subgrades and earthwork, to evaluate whether or not the conditions encountered are consistent with those assumed for design, and to provide additional recommendations during construction, if needed.

10. REFERENCES

American Association of State Highway and Transportation Officials (AASHTO 2024), LRFD Bridge

Design Specifications, Tenth Edition, dated 2024.

American Association of State Highway and Transportation Officials (AASHTO 1993), AASHTO Guide for Design of Pavement Structures, dated 1993.

CalTopo (2023), Slope and Aspect Data for Santa Margarita – California, retrieved from https://caltopo.com, accessed August 16, 2023.

https://caltopo.com/

Jacobs (Jacobs 2023), Black Mountain Road – ERFO Repairs, Los Padres National Forest, San Luis Obispo County, California, 100% Plans, dated August 8, 2023.

Jacobs (Jacobs 2025), Black Mountain Road, Los Padres National Forest, San Luis Obispo County, California, 100% Plans, dated August 26, 2025.

United States Department of Transportation – Federal Highway Administration (FHWA 2018), Federal Lands Highway Project Development and Design Manual (PPDM), issued July 2012 (with July 2018 revisions).

U.S. Department of Transportation, Federal Highway Administration. Standard Specifications for Construction of Roads and Bridges on Federal Highway Projects FP-24, U.S.

Wiegers, Mark O., Earl W. Hart, and Marc Delattre., 2015 (Wiegers 2015), Preliminary Geologic Map of the Santa Margarita 7.5' Quadrangle, San Luis Obispo County, California. Version 1.0. California Geological Survey, Scale 1:24,000.

World Weather Online (2025), Climate Santa Margarita – California and Weather averages Santa Margarita, www.worldweatheronline.com, accessed July 8, 2025.

Yeh and Associates, Inc. (Yeh 2023), Geotechnical Memorandum for ERFO Repairs for Black Mountain Road, CA ERFO FS LSPDR 2023-1(1B), Los Padres National Forest, San Luis Obispo County, California, date August 16, 2023.

Yeh and Associates, Inc. (Yeh 2025), Preliminary Pavement Structural Sections for Black Mountain Road, CA ERFO FS LSPDR 2023-1(1B), Los Padres National Forest, San Luis Obispo County, California, date June 18, 2025.

http://www.worldweatheronline.com/

PLATEPROJECT NAME:

PROJECT NUMBER: REVISION DATE:

Geotechnical • Geological • Construction Services

Parkhill Road

Begin Project StaƟon 100+00

CA ERFO FS LSPDR 2023-1(1B)

BLACK MOUNTAIN ROAD

LOS PADRES NATIONAL FOREST, CA

222-381C 7/7/2025

BORING LOCATION MAP

North

22000 feet

LEGEND:

No.

Boring LocaƟon (Yeh 2025)

Base Maps: Google Earth (2025).

Note: All locaƟons are approximate

25P-01

25P-06

25P-04

25P-05

25P-03

25P-07

25P-02

APPENDIX A – BORING LOGS AND DRILL RIG PHOTOS

DATE

7/1/2025

PROJECT NAME

CFL-Paso Robles Radar Road

Shrinkage Limit (ASTM D427)

Swell Potential (ASTM D4546)

Unconfined Compression - Soil (ASTM D2166) Unconfined Compression - Rock (ASTM D7012)

Unconsolidated Undrained Triaxial

(ASTM D2850)

Vane Shear (AASHTO T 223-96 [2004])

-200

VS

UW

UU

UC

Permeability (ASTM 5084)

Unit Weight (ASTM D4767, ASTM D7263)

200 Wash (ASTM D1140)

SILTY, CLAYEY SAND

Group Names

SC-SM

Graphic / Symbol Graphic / Symbol Group Names

Standard California Sampler (2.5" O.D.)

C

CL

CP

CR

CU

Corrosion, Sulfates, Chlorides (CTM 643; ASTM

D4972, ASTM G187, ASTM D4327)

Compaction Curve (ASTM D1557)

Direct Shear (ASTM D3080)

Expansion Index (ASTM D4829)

PP

PM

PL

PI

PA

P

OC

M

GRAVELLY ORGANIC SILT

GRAVELLY ORGANIC SILT with SAND

ORGANIC SILT

Well-graded SAND with CLAY and GRAVEL (or SILTY CLAY and GRAVEL)

SILTY, CLAYEY SAND with GRAVEL

CLAYEY SAND with GRAVEL

SILTY SAND with GRAVEL

GROUP SYMBOLS AND NAMES

DRILLING METHOD SYMBOLS

OL

EI

GC

GP

GC-GM

SANDY ORGANIC SILT

Lean CLAY with SAND Lean CLAY with GRAVEL

SANDY lean CLAY with GRAVEL

ORGANIC lean CLAY

GRAVELLY ORGANIC lean CLAY GRAVELLY ORGANIC lean CLAY with SAND

Fat CLAY

Elastic SILT with GRAVEL SANDY elastic SILT

SANDY elastic SILT with GRAVEL GRAVELLY elastic SILT GRAVELLY elastic SILT with SAND

ORGANIC elastic SILT

SANDY ORGANIC SILT with GRAVEL

CH

MH

OH

OL/OH

Rock Core Grab Sample

TV

SW

SL

SG

SE

R

Poorly graded SAND with SILT and GRAVEL

SANDY lean CLAY

GRAVELLY lean CLAY

ORGANIC lean CLAY with SAND ORGANIC lean CLAY with GRAVEL SANDY ORGANIC lean CLAY

SANDY ORGANIC lean CLAY with GRAVEL

Fat CLAY with SAND Fat CLAY with GRAVEL SANDY fat CLAY

SANDY fat CLAY with GRAVEL GRAVELLY fat CLAY GRAVELLY fat CLAY with SAND

ORGANIC fat CLAY ORGANIC fat CLAY with SAND ORGANIC fat CLAY with GRAVEL SANDY ORGANIC fat CLAY

Elastic SILT with SAND

Well-graded GRAVEL

Poorly graded GRAVEL with SILT

GRAVELLY lean CLAY with SAND

DS

SP-SC

SW

SP

Piston Sampler

SW-SM

SILTY, CLAYEY GRAVEL with SAND

CLAYEY GRAVEL with SAND

SILTY GRAVEL with SAND

Modified California Sampler (3" O.D.)

GRAVELLY SILT with SAND

SILT

ORGANIC SILT with SAND ORGANIC SILT with GRAVEL

Liquid Limit, Plastic Limit, Plasticity Index

(ASTM D4318)

Consolidation (ASTM D2435)

Collapse Potential (ASTM D5333)

Consolidated Undrained Triaxial (ASTM D4767)

Moisture Content (ASTM D2216)

Organic Content (ASTM D2974)

Particle Size Analysis (ASTM D422-63 [2007])

Point Load Index (ASTM D5731)

Standard Penetration Test (SPT) (2" O.D.)

OL

SC

GW

GW-GM

CL

CL-ML

ML

COBBLES and BOULDERS

BOULDERS

PT

SILTY GRAVEL

CLAYEY GRAVEL

SILTY, CLAYEY GRAVEL

SILTY SAND

CLAYEY SAND

SILTY CLAY

SILTY CLAY with SAND SILTY CLAY with GRAVEL

SANDY SILTY CLAY

SANDY SILTY CLAY with GRAVEL

GRAVELLY SILTY CLAY

GRAVELLY SILTY CLAY with SAND

SILT with SAND SILT with GRAVEL

SANDY SILT

SANDY SILT with GRAVEL

SANDY ORGANIC fat CLAY with GRAVEL GRAVELLY ORGANIC fat CLAY GRAVELLY ORGANIC fat CLAY with SAND

Elastic SILT

ORGANIC elastic SILT with GRAVEL SANDY elastic ELASTIC SILT

COBBLES

Well-graded GRAVEL with SAND

Well-graded GRAVEL with SILT

Well-graded GRAVEL with CLAY and SAND (or SILTY CLAY and SAND)

Well-graded SAND with CLAY (or SILTY CLAY)

Poorly graded GRAVEL

Poorly graded GRAVEL with CLAY (or SILTY CLAY)

Poorly graded SAND with SILT

Poorly graded SAND with CLAY (or SILTY CLAY)

Poorly graded SAND with CLAY and GRAVEL (or SILTY CLAY and GRAVEL)

Lean CLAY

ORGANIC elastic SILT with SAND

SANDY ORGANIC elastic SILT with GRAVEL GRAVELLY ORGANIC elastic SILT GRAVELLY ORGANIC elastic SILT with SAND

GW-GC

GP-GM

GP-GC

GM

Well-graded SAND with SILT

SW-SC

SP-SM

GRAVELLY SILT

ORGANIC SOIL

ORGANIC SOIL with SAND ORGANIC SOIL with GRAVEL

SANDY ORGANIC SOIL

SANDY ORGANIC SOIL with GRAVEL

GRAVELLY ORGANIC SOIL

GRAVELLY ORGANIC SOIL with SAND

OH

SM

Auger Drilling

FIELD AND LABORATORY TESTS

WATER LEVEL SYMBOLS

Dynamic Cone or Hand Driven Diamond CoreRotary Drilling

Static Water Level Reading (long-term)

Bulk Sample Other (see remarks)

Static Water Level Reading (short-term)

First Water Level Reading (during drilling)

SHEET

SAMPLER GRAPHIC SYMBOLS

PEAT

Well-graded GRAVEL with SILT and SAND

Well-graded GRAVEL with CLAY (or SILTY CLAY)

Well-graded SAND

Well-graded SAND with GRAVEL

Well-graded SAND with SILT and GRAVEL

Poorly graded GRAVEL with SAND

Poorly graded GRAVEL with SILT and SAND

Poorly graded GRAVEL with CLAY and SAND (or SILTY CLAY and SAND)

Poorly graded SAND

Poorly graded SAND with GRAVEL

Pressure Meter

Pocket Penetrometer

Pocket Torvane

R-Value (CTM 301)

Sand Equivalent (CTM 217)

Specific Gravity (AASHTO T 100)

REPORT TITLE

LEGEND FOR SOIL CLASSIFICATION

Thin-Walled Tube

A1 of 10

6 11813

CR (pH = 6.37, r = 8,112 ohm-cm, SO4

2- = 27 mg/kg, Cl- = <2 mg/kg) CP ( D, MAX = 126 pcf, wOPT = 8%)

PA (2% G, 89% S, 9% F)

2'' ASPHALT CONCRETE.

Well-graded SAND with CLAY (SW-SC), medium dense, dark brown, moist, coarse grained sand, trace fine gravel (Alluvium).

Fine subangular to subrounded gravel. Chert, quartz?.

Bottom of borehole at 6.5 ft bgs

This Boring Record was developed in accordance with the FHWA Description and Identification Guidelines (2017) and FHWA Rock Characterization Guidelines (2017) except as noted on the Soil or Rock Legend or below.

G

TOTAL DEPTH OF BORING

6.5 ft

GROUNDWATER

READINGS N/A

FINAL BY

J. Frame

DRILL RIG

CME 55

WEATHER NOTES

Sunny, cool, breezey

BORING NUMBER

25P-01

SURFACE ELEVATION

1839.0 ft

LOGGED BY

J. Frame

DRILLER

BC/DC

BEGIN DATE

6-6-25

COMPLETION DATE

6-6-25

DRILLING METHOD

8" Hollow-Stem Auger

HAMMER TYPE

140 lb donut at 30" drop BOREHOLE LOCATION (Lat/Long or North/East and Datum)

35.349447°/-120.350989°

DURING DRILLING

N/A

AFTER DRILLING (DATE)

BOREHOLE LOCATION (Offset, Station, Line)

Sta. 106+10

LOCATION DESCRIPTION

Roadway

BACKFILLED WITH

cuttings, capped with quickrete.

M at er ia l G ra ph ic s

PROJECT NUMBER

222-381C

SHEET

M oi st ur e C on te nt

D E

P T

H ft)

BORING NUMBER

25P-01

D ry

U ni t W ei gh t

(p cf

B lo w s pe r in

R ec ov er y

E

LE

V A

T

IO

N ft)

REVISION DATE

7/1/2025

D ril lin g

M et ho d

C as in g

D ep th

Remarks

S he ar S tr en gt h

(k sf

DESCRIPTION

S am pl e

Lo ca tio n

S am pl e

N um be r

B lo w s pe r fo ot

R Q

D

F F

(F ra ct ur es /F oo t)

PROJECT NAME

CFL-Paso Robles Radar Road

B

R

S T

A N

D A

R D

-3

1C -C

F L.

G P

J C

A

LI

F O

R N

IA

Y

E H

L

IB

R A

R Y

Y

E H

V

JA

N

U A

R Y

C

F L.

G

LB

/9

/2

A2 of 10

2 11149 50/3"

50/2"

-200 (1% G, 85% S, 14% F) R (R-Value = 78)

PA (0% G, 82% S, 18% F)

4'' ASPHALT CONCRETE.

CLAYEY SAND (SC), very dense, light to dark brown, dry, coarse SAND, (Alluvium).

Bottom of borehole at 5.7 ft bgs

This Boring Record was developed in accordance with the FHWA Description and Identification Guidelines (2017) and FHWA Rock Characterization Guidelines (2017) except as noted on the Soil or Rock Legend or below.

F

TOTAL DEPTH OF BORING

5.7 ft

GROUNDWATER

READINGS N/A

FINAL BY

J. Frame

DRILL RIG

CME 55

WEATHER NOTES

Sunny, warm

BORING NUMBER

25P-02

SURFACE ELEVATION

1979.0 ft

LOGGED BY

J. Frame

DRILLER

BC/DC

BEGIN DATE

6-6-25

COMPLETION DATE

6-6-25

DRILLING METHOD

8" Hollow-Stem Auger

HAMMER TYPE

140 lb donut at 30" drop BOREHOLE LOCATION (Lat/Long or North/East and Datum)

35.357706°/-120.345858°

DURING DRILLING

N/A

AFTER DRILLING (DATE)

BOREHOLE LOCATION (Offset, Station, Line)

Sta. 144+40

LOCATION DESCRIPTION

Roadway

BACKFILLED WITH

cuttings, capped with quickrete.

M at er ia l G ra ph ic s

PROJECT NUMBER

222-381C

SHEET

M oi st ur e C on te nt

D E

P T

H ft)

BORING NUMBER

25P-02

D ry

U ni t W ei gh t

(p cf

B lo w s pe r in

R ec ov er y

E

LE

V A

T

IO

N ft)

REVISION DATE

7/1/2025

D ril lin g

M et ho d

C as in g

D ep th

Remarks

S he ar S tr en gt h

(k sf

DESCRIPTION

S am pl e

Lo ca tio n

S am pl e

N um be r

B lo w s pe r fo ot

R Q

D

F F

(F ra ct ur es /F oo t)

PROJECT NAME

CFL-Paso Robles Radar Road

B

R

S T

A N

D A

R D

-3

1C -C

F L.

G P

J C

A

LI

F O

R N

IA

Y

E H

L

IB

R A

R Y

Y

E H

V

JA

N

U A

R Y

C

F L.

G

LB

/9

/2 ref 9" ref 8"

A3 of 10

10 11511

PA (2% G, 52% S, 46% F)

CR (pH = 5.83, r = 649 ohm-cm, SO4

2- = 111 mg/kg, Cl- = 48 mg/kg)

-200 (1% G, 61% S, 38% F)

4'' ASPHALT CONCRETE.

CLAYEY SAND (SC), medium dense, light brown, moist, (Decomposed Granite).

Dense, light brown, dry, white mottling.

Bottom of borehole at 6.5 ft bgs

This Boring Record was developed in accordance with the FHWA Description and Identification Guidelines (2017) and FHWA Rock Characterization Guidelines (2017) except as noted on the Soil or Rock Legend or below.

E

TOTAL DEPTH OF BORING

6.5 ft

GROUNDWATER

READINGS N/A

FINAL BY

J. Frame

DRILL RIG

CME 55

WEATHER NOTES

Sunny, warm

BORING NUMBER

25P-03

SURFACE ELEVATION

2403.0 ft

LOGGED BY

J. Frame

DRILLER

BC/DC

BEGIN DATE

6-6-25

COMPLETION DATE

6-6-25

DRILLING METHOD

8" Hollow-Stem Auger

HAMMER TYPE

140 lb donut at 30" drop BOREHOLE LOCATION (Lat/Long or North/East and Datum)

35.364890°/-120.337473°

DURING DRILLING

N/A

AFTER DRILLING (DATE)

BOREHOLE LOCATION (Offset, Station, Line)

Sta. 198+00

LOCATION DESCRIPTION

Roadway

BACKFILLED WITH

cuttings, capped with quickrete.

M at er ia l G ra ph ic s

PROJECT NUMBER

222-381C

SHEET

M oi st ur e C on te nt

D E

P T

H ft)

BORING NUMBER

25P-03

D ry

U ni t W ei gh t

(p cf

B lo w s pe r in

R ec ov er y

E

LE

V A

T

IO

N ft)

REVISION DATE

7/1/2025

D ril lin g

M et ho d

C as in g

D ep th

Remarks

S he ar S tr en gt h

(k sf

DESCRIPTION

S am pl e

Lo ca tio n

S am pl e

N um be r

B lo w s pe r fo ot

R Q

D

F F

(F ra ct ur es /F oo t)

PROJECT NAME

CFL-Paso Robles Radar Road

B

R

S T

A N

D A

R D

-3

1C -C

F L.

G P

J C

A

LI

F O

R N

IA

Y

E H

L

IB

R A

R Y

Y

E H

V

JA

N

U A

R Y

C

F L.

G

LB

/9

/2

A4 of 10

6 11721

50/2"

50/6"

CP ( D, MAX = 126 pcf, wOPT = 8%)

-200 (0% G, 88% S, 11% F)

1'' ASPHALT CONCRETE.

Well-graded SAND with CLAY (SW-SC), very dense, yellowish brown, moist, trace GRAVEL, (Decomposed Granite).

Yellow, dry.

Bottom of borehole at 5.5 ft bgs

This Boring Record was developed in accordance with the FHWA Description and Identification Guidelines (2017) and FHWA Rock Characterization Guidelines (2017) except as noted on the Soil or Rock Legend or below.

D

TOTAL DEPTH OF BORING

5.5 ft

GROUNDWATER

READINGS N/A

FINAL BY

J. Frame

DRILL RIG

CME 55

WEATHER NOTES

Sunny, warm, breezey

BORING NUMBER

25P-04

SURFACE ELEVATION

2851.0 ft

LOGGED BY

J. Frame

DRILLER

BC/DC

BEGIN DATE

6-6-25

COMPLETION DATE

6-6-25

DRILLING METHOD

8" Hollow-Stem Auger

HAMMER TYPE

140 lb donut at 30" drop BOREHOLE LOCATION (Lat/Long or North/East and Datum)

35.371065°/-120.329232°

DURING DRILLING

N/A

AFTER DRILLING (DATE)

BOREHOLE LOCATION (Offset, Station, Line)

Sta. 267+30

LOCATION DESCRIPTION

Roadway

BACKFILLED WITH

cuttings, capped with quickrete.

M at er ia l G ra ph ic s

PROJECT NUMBER

222-381C

SHEET

M oi st ur e C on te nt

D E

P T

H ft)

BORING NUMBER

25P-04

D ry

U ni t W ei gh t

(p cf

B lo w s pe r in

R ec ov er y

E

LE

V A

T

IO

N ft)

REVISION DATE

7/1/2025

D ril lin g

M et ho d

C as in g

D ep th

Remarks

S he ar S tr en gt h

(k sf

DESCRIPTION

S am pl e

Lo ca tio n

S am pl e

N um be r

B lo w s pe r fo ot

R Q

D

F F

(F ra ct ur es /F oo t)

PROJECT NAME

CFL-Paso Robles Radar Road

B

R

S T

A N

D A

R D

-3

1C -C

F L.

G P

J C

A

LI

F O

R N

IA

Y

E H

L

IB

R A

R Y

Y

E H

V

JA

N

U A

R Y

C

F L.

G

LB

/9

/2 ref 14" ref 6"

A5 of 10

9 11714

CR (pH = 6.33, r = 5,949 ohm-cm, SO4

2- = 14 mg/kg, Cl- = <2 mg/kg)

-200 (0% G, 61% S, 39% F)

3'' ASPHALT CONCRETE.

CLAYEY SAND (SC), medium dense, dark yellowish brown, moist, coarse SAND, (Decomposed Granite).

Dense, light to yellowish brown, moist, trace GRAVEL, coarse SAND.

Bottom of borehole at 6.5 ft bgs

This Boring Record was developed in accordance with the FHWA Description and Identification Guidelines (2017) and FHWA Rock Characterization Guidelines (2017) except as noted on the Soil or Rock Legend or below.

C

TOTAL DEPTH OF BORING

6.5 ft

GROUNDWATER

READINGS N/A

FINAL BY

J. Frame

DRILL RIG

CME 55

WEATHER NOTES

Sunny, hot, breezey

BORING NUMBER

25P-05

SURFACE ELEVATION

2909.0 ft

LOGGED BY

J. Frame

DRILLER

BC/DC

BEGIN DATE

6-6-25

COMPLETION DATE

6-6-25

DRILLING METHOD

8" Hollow-Stem Auger

HAMMER TYPE

140 lb donut at 30" drop BOREHOLE LOCATION (Lat/Long or North/East and Datum)

35.383062°/-120.349831°

DURING DRILLING

N/A

AFTER DRILLING (DATE)

BOREHOLE LOCATION (Offset, Station, Line)

Sta. 361+50

LOCATION DESCRIPTION

Roadway

BACKFILLED WITH

cuttings, capped with quickrete.

M at er ia l G ra ph ic s

PROJECT NUMBER

222-381C

SHEET

M oi st ur e C on te nt

D E

P T

H ft)

BORING NUMBER

25P-05

D ry

U ni t W ei gh t

(p cf

B lo w s pe r in

R ec ov er y

E

LE

V A

T

IO

N ft)

REVISION DATE

7/1/2025

D ril lin g

M et ho d

C as in g

D ep th

Remarks

S he ar S tr en gt h

(k sf

DESCRIPTION

S am pl e

Lo ca tio n

S am pl e

N um be r

B lo w s pe r fo ot

R Q

D

F F

(F ra ct ur es /F oo t)

PROJECT NAME

CFL-Paso Robles Radar Road

B

R

S T

A N

D A

R D

-3

1C -C

F L.

G P

J C

A

LI

F O

R N

IA

Y

E H

L

IB

R A

R Y

Y

E H

V

JA

N

U A

R Y

C

F L.

G

LB

/9

/2

A6 of 10

8 11418

R (R-Value = 16)

-200 (1% G, 73% S, 26% F)

PA (0% G, 78% S, 21% F)

2.5'' ASPHALT CONCRETE.

CLAYEY SAND (SC), dense, brown, moist, (Decomposed Granite).

Very dense, dry.

Bottom of borehole at 6.5 ft bgs

This Boring Record was developed in accordance with the FHWA Description and Identification Guidelines (2017) and FHWA Rock Characterization Guidelines (2017) except as noted on the Soil or Rock Legend or below.

B

TOTAL DEPTH OF BORING

6.5 ft

GROUNDWATER

READINGS N/A

FINAL BY

J. Frame

DRILL RIG

CME 55

WEATHER NOTES

Sunny, hot, breezey

BORING NUMBER

25P-06

SURFACE ELEVATION

3400.0 ft

LOGGED BY

J. Frame

DRILLER

BC/DC

BEGIN DATE

6-6-25

COMPLETION DATE

6-6-25

DRILLING METHOD

8" Hollow-Stem Auger

HAMMER TYPE

140 lb donut at 30" drop BOREHOLE LOCATION (Lat/Long or North/East and Datum)

35.394723°/-120.360432°

DURING DRILLING

N/A

AFTER DRILLING (DATE)

BOREHOLE LOCATION (Offset, Station, Line)

Sta. 424+50

LOCATION DESCRIPTION

Roadway

BACKFILLED WITH

cuttings, capped with quickrete.

M at er ia l G ra ph ic s

PROJECT NUMBER

222-381C

SHEET

M oi st ur e C on te nt

D E

P T

H ft)

BORING NUMBER

25P-06

D ry

U ni t W ei gh t

(p cf

B lo w s pe r in

R ec ov er y

E

LE

V A

T

IO

N ft)

REVISION DATE

7/1/2025

D ril lin g

M et ho d

C as in g

D ep th

Remarks

S he ar S tr en gt h

(k sf

DESCRIPTION

S am pl e

Lo ca tio n

S am pl e

N um be r

B lo w s pe r fo ot

R Q

D

F F

(F ra ct ur es /F oo t)

PROJECT NAME

CFL-Paso Robles Radar Road

B

R

S T

A N

D A

R D

-3

1C -C

F L.

G P

J C

A

LI

F O

R N

IA

Y

E H

L

IB

R A

R Y

Y

E H

V

JA

N

U A

R Y

C

F L.

G

LB

/9

/2

A7 of 10

6 10219

CR (pH = 6.86, r = 25 ohm-cm, SO4

2- = 64 mg/kg, Cl- = 3 mg/kg) CP ( D, MAX = 127 pcf, wOPT = 9%) -200 (2% G, 72% S, 25% F)

PA (2% G, 72% S, 25% F)

2.5'' ASPHALT CONCRETE.

CLAYEY SAND (SC), dense, light brown, dry, rounded GRAVEL, (Decomposed Granite).

Cobbles.

Very dense, brown, moist to dry, fine GRAVEL, white mottling.

Bottom of borehole at 6.5 ft bgs

This Boring Record was developed in accordance with the FHWA Description and Identification Guidelines (2017) and FHWA Rock Characterization Guidelines (2017) except as noted on the Soil or Rock Legend or below.

A

TOTAL DEPTH OF BORING

6.5 ft

GROUNDWATER

READINGS N/A

FINAL BY

J. Frame

DRILL RIG

CME 55

WEATHER NOTES

Sunny, hot, breezey

BORING NUMBER

25P-07

SURFACE ELEVATION

3537.0 ft

LOGGED BY

J. Frame

DRILLER

BC/DC

BEGIN DATE

6-6-25

COMPLETION DATE

6-6-25

DRILLING METHOD

8" Hollow-Stem Auger

HAMMER TYPE

140 lb donut at 30" drop BOREHOLE LOCATION (Lat/Long or North/East and Datum)

35.394228°/-120.351840°

DURING DRILLING

N/A

AFTER DRILLING (DATE)

BOREHOLE LOCATION (Offset, Station, Line)

Sta. 454+10

LOCATION DESCRIPTION

Roadway

BACKFILLED WITH

cuttings, capped with quickrete.

M at er ia l G ra ph ic s

PROJECT NUMBER

222-381C

SHEET

M oi st ur e C on te nt

D E

P T

H ft)

BORING NUMBER

25P-07

D ry

U ni t W ei gh t

(p cf

B lo w s pe r in

R ec ov er y

E

LE

V A

T

IO

N ft)

REVISION DATE

7/1/2025

D ril lin g

M et ho d

C as in g

D ep th

Remarks

S he ar S tr en gt h

(k sf

DESCRIPTION

S am pl e

Lo ca tio n

S am pl e

N um be r

B lo w s pe r fo ot

R Q

D

F F

(F ra ct ur es /F oo t)

PROJECT NAME

CFL-Paso Robles Radar Road

B

R

S T

A N

D A

R D

-3

1C -C

F L.

G P

J C

A

LI

F O

R N

IA

Y

E H

L

IB

R A

R Y

Y

E H

V

JA

N

U A

R Y

C

F L.

G

LB

/9

/2

A8 of 10

DRAFT Geotechnical and Pavement Report Yeh Project No. 222-381C Black Mountain Road – CA ERFO FS LSPDR 2023-1(1B) July 8, 2025

25P-01

Black Mountain Road St 106+10 25P-02

Black Mountain Road St 144+40

25P-03

Black Mountain Road St 198+00 25P-04

Black Mountain Road St 267+30

<<A-1 of n>>

A9 of 10

DRAFT Geotechnical and Pavement Report Yeh Project No. 222-381C Black Mountain Road – CA ERFO FS LSPDR 2023-1(1B) July 8, 2025

25P-05

Black Mountain Road St 361+50 25P-06

Black Mountain Road St 424+50

25P-07 Black Mountain Road St 454+10

<<A-1 of n>>

A10 of 10

APPENDIX B – RESULTS OF LABORATORY TESTING

25P-01 G 0.0 BULK -- -- -- -- -- -- -- -- 6.37 8,112 27 <2 126 8 -- -- -- Well-graded SAND with CLAY (SW-SC)

25P-01 13 1.0 MCAL 125 118 6 -- -- -- -- -- -- -- -- -- -- -- -- -- -- Well-graded SAND with CLAY (SW-SC)

25P-01 14 5.0 SPT -- -- -- 2 89 9 -- -- -- -- -- -- -- -- -- -- -- Well-graded SAND with CLAY (SW-SC)

25P-02 F 0.0 BULK -- -- -- 1 85 14 -- -- -- -- -- -- -- -- 78 -- -- CLAYEY SAND (SC)

25P-02 11 1.0 MCAL 113 111 2 -- -- -- -- -- -- -- -- -- -- -- -- -- -- CLAYEY SAND (SC)

25P-02 12 5.0 SPT -- -- -- 0 82 18 -- -- -- -- -- -- -- -- -- -- -- CLAYEY SAND (SC)

25P-03 E 0.0 BULK -- -- -- 2 52 46 -- -- 5.83 649 111 48 -- -- -- -- -- CLAYEY SAND (SC)

25P-03 9 1.0 MCAL 126 115 10 -- -- -- -- -- -- -- -- -- -- -- -- -- -- CLAYEY SAND (SC)

25P-03 10 5.0 SPT -- -- -- 1 61 38 -- -- -- -- -- -- -- -- -- -- -- CLAYEY SAND (SC)

25P-04 D 0.0 BULK -- -- -- -- -- -- -- -- -- -- -- -- 126 8 -- -- -- Well-graded SAND with CLAY (SW-SC)

25P-04 7 1.0 MCAL 125 117 6 -- -- -- -- -- -- -- -- -- -- -- -- -- -- Well-graded SAND with CLAY (SW-SC)

25P-04 8 5.0 SPT -- -- -- 0 88 11 -- -- -- -- -- -- -- -- -- -- -- Well-graded SAND with CLAY (SW-SC)

25P-05 C 0.0 BULK -- -- -- -- -- -- -- -- 6.33 5,949 14 <2 -- -- -- -- -- CLAYEY SAND (SC)

25P-05 5 1.0 MCAL 128 117 9 -- -- -- -- -- -- -- -- -- -- -- -- -- -- CLAYEY SAND (SC)

25P-05 6 5.0 SPT -- -- -- 0 61 39 -- -- -- -- -- -- -- -- -- -- -- CLAYEY SAND (SC)

25P-06 B 0.0 BULK -- -- -- -- -- -- -- -- -- -- -- -- -- -- 16 -- -- CLAYEY SAND (SC)

25P-06 3 1.0 MCAL 123 114 8 1 73 26 -- -- -- -- -- -- -- -- -- -- -- CLAYEY SAND (SC)

25P-06 4 5.0 SPT -- -- -- 0 78 21 -- -- -- -- -- -- -- -- -- -- -- CLAYEY SAND (SC)

25P-07 A 0.0 BULK -- -- -- -- -- -- -- -- 6.86 25 64 3 127 9 -- -- -- CLAYEY SAND (SC)

25P-07 1 1.0 MCAL 108 102 6 2 72 25 -- -- -- -- -- -- -- -- -- -- -- CLAYEY SAND (SC)

Sample Information

SUMMARY OF LABORATORY TEST RESULTS

Boring No.

Sample No.

USCS…