A17_-_Geotechnical_Report.pdf

G E O T E C H N I C A L R E P O R T

MULCAHEY DRIVE AND POL ROAD ROADWAY

REPAIR AND MAIN ENTRANCE UPGRADE PROJECT

AIR NATIONAL GUARD BASE FACILITY

CHANNEL ISLANDS, CALIFORNIA

Prepared for

California Air National Guard 146th Airlift Wing Channel Islands, CA

Project No. 60439605

May 26, 2017

May 26, 2017

Major Shane Patty Contracting Office Representative Channel Islands Air National Guard Base Facility Channel Islands, CA

Subject: Geotechnical Report Mulcahey Drive and Pol Road Roadway Repair and Main Entrance Upgrade Project Air Nation Guard Base Facility Channel Islands, California

Major Patty, AECOM is pleased to present the results of our preliminary geotechnical investigation performed for the Air National Guard Base Roadway Repair and Main Entrance Upgrade project located in Channel Islands, California.

The scope of work included performing site-specific subsurface exploration, geotechnical laboratory testing, engineering analyses, and preparation of this report. This report presents the findings from our subsurface exploration, our interpretation of the subsurface conditions encountered, and conclusions and recommendations pertaining to design and construction of the proposed roadway improvements and canopy structure. Based on the results from our geotechnical investigation, the project is feasible from a geotechnical standpoint, provided the recommendations in this report are followed. Please contact us if you have any questions.

Sincerely, AECOM

Praveen Yerra, P.E. Paul A. Salter, P.G., C.H.G, C.E.G.

Senior Project Engineer Senior Engineering Geologist CE 81209 Exp. 9/30/17 CEG 2298 Exp. 01/31/17

AECOM

999 Town and Country Road Orange, CA 92868 Tel: 714-567-2400 Fax: 714-567-2441

Table of Contents

1.0 INTRODUCTION ...................................................................................................................................... 1-1

1.1 OBJECTIVES OF INVESTIGATION................................................................................................................ 1-1

1.2 PROJECT DESCRIPTION.............................................................................................................................. 1-1

1.3 SCOPE OF WORK ....................................................................................................................................... 1-1

2.0 GEOTECHNICAL INVESTIGATION AND LABORATORY TESTING.......................................... 2-1

2.1 REVIEW OF EXISTING DATA...................................................................................................................... 2-1

2.2 FIELD INVESTIGATION .............................................................................................................................. 2-1

2.2.1 General ................................................................................................................................................ 2-1

2.2.2 Exploratory Borings ............................................................................................................................ 2-1

2.2.3 Soil Logging......................................................................................................................................... 2-2

2.2.4 Sampling and Field Tests..................................................................................................................... 2-2

2.3 LABORATORY TESTING............................................................................................................................. 2-2

3.0 GEOLOGY AND SUBSURFACE CONDITIONS.................................................................................. 3-1

3.1 REGIONAL GEOLOGIC SETTING................................................................................................................. 3-1

3.2 LOCAL GEOLOGIC SETTING ...................................................................................................................... 3-2

3.3 SUBSURFACE CONDITIONS........................................................................................................................ 3-2

3.4 GROUNDWATER ........................................................................................................................................ 3-2

4.0 PAVEMENT RECOMMENDATIONS.................................................................................................... 4-1

4.1 SUMMARY OF FINDINGS............................................................................................................................ 4-1

4.2 SUBGRADE CONDITIONS ........................................................................................................................... 4-1

4.3 PAVEMENT DESIGN RECOMMENDATIONS ................................................................................................. 4-1

4.3.1 Methodology ........................................................................................................................................ 4-2

4.3.2 Reconstruction ..................................................................................................................................... 4-3

4.3.3 Alternative............................................................................................................................................ 4-3

5.0 CONSTRUCTION REQUIREMENTS.................................................................................................... 5-1

5.1 MATERIALS AVAILABLE ........................................................................................................................... 5-1

5.2 GENERAL EARTHWORK REQUIREMENTS................................................................................................... 5-1

5.2.1 Site Preparation and Earthwork.......................................................................................................... 5-1

5.2.2 Compaction.......................................................................................................................................... 5-1

5.2.3 Demolition ........................................................................................................................................... 5-1

5.2.4 Excavations.......................................................................................................................................... 5-2

5.2.5 Material Specifications ........................................................................................................................ 5-2

5.3 SITE DRAINAGE ........................................................................................................................................ 5-2

5.4 SPECIFICATIONS........................................................................................................................................ 5-3

6.0 FOUNDATION RECOMMENDATIONS ............................................................................................... 6-1

6.1 SHALLOW FOUNDATIONS.......................................................................................................................... 6-1

6.1.1 Spread Footing Foundations ............................................................................................................... 6-1

6.1.2 Resistance to Lateral Loads................................................................................................................. 6-1

6.1.3 Site Preparation and Grading ............................................................................................................. 6-1

6.1.4 Fill and Backfill ................................................................................................................................... 6-2

7.0 CONSTRUCTION CONSIDERATIONS ................................................................................................ 7-1

7.1 CONSTRUCTION ADVISORIES .................................................................................................................... 7-1

7.2 PRECONSTRUCTION SURVEY AND CONSTRUCTION MONITORING ............................................................. 7-1

7.3 CONTAMINATED SOIL CONSIDERATIONS .................................................................................................. 7-1

7.4 CUTS AND EXCAVATIONS ......................................................................................................................... 7-1

7.5 TEMPORARY EXCAVATIONS...................................................................................................................... 7-1

7.6 SITE DEWATERING AND CONTROL OF WATER DURING CONSTRUCTION ................................................... 7-2

Table of Contents

8.0 UNCERTAINTIES AND LIMITATIONS............................................................................................... 8-1

List of Tables, Figures and Appendices

FIGURES

Figure 1 Site Location Map Figure 2 Geotechnical Exploration Plan Figure 3 Regional Geologic Map Figure 4 Historically Highest Ground Water Map

APPENDICES

Appendix A Field Exploration Appendix B Laboratory Testing Appendix C Analyses and Calculations Appendix D References

Geotechnical Report Air National Guard Base Facility

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1.0 INTRODUCTION

1.1 OBJECTIVES OF INVESTIGATION

This report presents the results of AECOM preliminary geotechnical investigation performed for the proposed roadway improvements at the Channel Islands Air National Guard Base facility located at 100 Mulcahey Drive, Port Hueneme, California. The location of the project is shown on Figure 1. The proposed work includes 1) rehabilitation of the existing roadway on Mulcahey Drive and POL Road 2) reconfiguring and upgrading the main gate entrance, and 3) constructing a new vehicle/truck inspection area that includes an overhead canopy structure near the existing guard shack. This report provides findings from our subsurface explorations, geotechnical laboratory testing, the geologic, and pavement and soil conditions, and presents our geotechnical recommendations for rehabilitation of the roadway and recommendations for the proposed vehicle inspection structure adjacent to the existing guard shack.

Conclusions and recommendations presented in this report are based on subsurface conditions encountered at our exploration locations. As subsurface conditions may vary at different locations, these conclusions and recommendations should not be extrapolated to other areas, or used for other facilities, without our prior review.

1.2 PROJECT DESCRIPTION

The site is located at the 146th Airlift wing Channel Islands Air National Guard Station (CIANGS), adjacent to the Point Mugu Naval Air Station in Port Hueneme, California. The major cross streets in the vicinity of the project site are East Hueneme Road and Pacific Coast Highway, as shown on Figure 2.

The approximate site coordinates are 34.141925° N and 119.112720° W. The primary access to CIANGS is obtained via Mulcahey Drive. POL Road provides a secondary access to the base facility but is not frequently used due to security concerns. Primary vehicular traffic consists of light duty trucks and maintenance vehicles. The roadways were initially constructed in the late 1980s and have had several phases of repairs. The client has requested an evaluation of the existing roadways and recommendations to provide a longer-term pavement design life, assumed to be 20 years.

1.3 SCOPE OF WORK

The following tasks were included in this preliminary investigation:

1. Prepared of a project specific Health and Safety Plan (HASP).

2. Coordinated field work with representatives from the Air National Guard Base Facility.

3. Notified Underground Service Alert (USA) in advance of field work.

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4. No permits were necessary as it is a private property.

5. Explored subsurface conditions by drilling five (5) hollow-stem auger (HSA) borings to a maximum depth of 25.5 feet below ground surface (bgs), logged the subsurface strata, and collected soil samples for laboratory analyses.

6. Backfilled the HSA boreholes with soil cuttings/bentonite chips/cement grout after completion of explorations.

7. Soil samples collected during drilling were transported to AECOM’s laboratory for geotechnical testing and soil classification.

8. Performed engineering analyses to evaluate pavement structure section material and thickness;

and

9. Prepared this report presenting our findings and recommendations.

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2.0 GEOTECHNICAL INVESTIGATION AND LABORATORY TESTING

The preliminary geotechnical investigation included a review of available geotechnical and geologic information, completion of subsurface explorations, and laboratory testing on selected soil samples to evaluate physical properties.

2.1 REVIEW OF EXISTING DATA

The site has been characterized by previous subsurface investigations performed during original construction of the base facility starting in the late 1980s. The preparation of this report relied on available geological and geotechnical documents as well as the geotechnical exploration conducted during the current phase of preliminary design.

2.2 FIELD INVESTIGATION

2.2.1 General

The field investigation, performed on November 12, 2015, consisted of drilling four geotechnical borings to explore subsurface conditions and to collect samples for laboratory testing. An additional boring was drilled to a maximum depth of 25.5 feet below ground surface on May 4th, 2017 accommodating the revision in planned location of the proposed vehicle inspection structure. The locations of the borings are shown on Figure 2. The boring locations were selected based on the proposed roadway improvements as well as to supplement the existing geotechnical borings that were performed by others in the recent past.

Details of the field investigation, including sampling procedures are presented in Appendix A.

2.2.2 Exploratory Borings

Five exploratory borings (designated B-15-001 through B-15-004 and B-17-005) were drilled at the locations shown on Figure 2.

The HSA borings were drilled using a CME 75 drill rig, advancing hollow stem augers with an 8-inch diameter bullet-tooth bit. Borings B-15-001 through B-15-003 were drilled to a maximum depth of 5 feet bgs, boring B-15-004 was drilled to a maximum depth of 21.5 feet bgs and boring B-17-005 was drilled to a maximum depth of 25.5 feet bgs. The upper 2.5 feet of subgrade was hand augured to clear for possible utilities. The soils encountered during drilling were visually classified in accordance with the Unified Soil Classification System (USCS).

The borings were backfilled using soil cuttings and bentonite chips up to 1 foot bgs. The upper 1 foot was backfilled with cement grout to the existing ground surface for locations that were drilled within the

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2-2 pavement section. The most recent boring B-17-005 was backfilled with bentonite slurry for the entire depth of the boring. The surface was reinstated to match existing ground conditions.

2.2.3 Soil Logging

AECOM’s field representative visually classified the soil samples and cuttings and maintained a record of subsurface materials encountered in the exploratory borings. A description of the field program, different soil types encountered during drilling, and other information are shown on the boring logs presented in Appendix A.

2.2.4 Sampling and Field Tests

Where subsurface conditions permitted, relatively undisturbed drive sampling and standard penetration tests (SPT) were performed in an alternating order at 5 foot vertical intervals in borings B-15-004 and B- 17-005. Drive samples were obtained using a modified California soil sampler (2.42-inch inside diameter, 3.0-inch outside diameter) that contained three 6-inch long liners. The SPTs were performed with an SPT sampler (1.4 inch inside diameter), without liners, in accordance with ASTM D1586 guidelines. Both SPT and California samplers were driven 18 inches into the subsurface soils using a 140-pound automatic hammer with successive 30-inch drops. The number of blows (the “N” value) required to drive the last 12 inches of the sampler are recorded on the boring logs. Bulk samples were collected from the shallow borings (5 feet) for evaluating the characteristics of the soil necessary for pavement design.

2.3 LABORATORY TESTING

Soil samples obtained from the borings were carefully sealed and packaged in the field to reduce moisture loss and disturbance. The samples were then delivered to AECOM’s geotechnical laboratory, located in Santa Ana, California where they were further examined and classified. Laboratory testing was performed on selected samples to confirm the field visual classification of the soils, and to evaluate their physical properties. Tests performed by AECOM included:

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Soil classification (ASTM D2487);

Moisture content and dry unit weight test (ASTM D2216 and D7263);

Atterberg limits for fine-grained materials (ASTM D4318);

Grain size analysis (ASTM D422, D1140);

Direct shear test (ASTM D3080);

Consolidation test (ASTM D2435);

Unconfined Compression (ASTM D2166); and, Expansion Index (ASTM D4829).

A description of the laboratory testing and the test results are presented in Appendix B. For reference, results from moisture content and dry density tests, plasticity index tests, and percent fines analyses of soils are also shown on the boring logs, presented in Appendix A.

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3.0 GEOLOGY AND SUBSURFACE CONDITIONS

The site geology and subsurface conditions have been characterized based on review of the published geologic literature, previous site investigations (Ninyo & Moore (N&M), 2010) and the field and laboratory programs undertaken for the current investigation.

3.1 REGIONAL GEOLOGIC SETTING

The project site is situated within the Santa Clara River flood plain, about 6 miles south of the river channel, within the Transverse Ranges geomorphic province. The Transverse Ranges are characterized by a complex series of mountain ranges, intervening valleys, and active faults with dominant east-west trends. The nearest hills are the Santa Monica Mountains, rising above the flood plain about 2 miles southeast of the project site, where the underlying rocks are predominantly early to mid-Miocene age interbedded siltstone, sandstone and shale of the Topanga Formation, overlain and intruded by Conejo Volcanics (principally basalt, andesite and dacite).

The project site is located in a seismically active area dominated by numerous active faults that have formed along a tectonic plate boundary known as the San Andreas transform zone. The San Andreas transform zone, which separates the North American plate to the east from the Pacific plate to the west, is dominated by northwest trending, right lateral, strike-slip faults of the San Andreas fault system. In the Transverse Ranges the right lateral strike slip environment of the San Andreas fault system is effected by a north-south component of compression that is caused by a convergent left bend of the San Andreas fault. This north-south directed compression is expressed by thrust, reverse or oblique slip faults and folds that trend approximately east-west.

Major east-west trending reverse or thrust faults in the vicinity of the project site include the Santa Monica-Hollywood-Raymond fault system which is located about 4.4 miles (7 km) to the southeast of the site, and the Simi-Santa Rosa fault which is located about 5.2 miles (8.9 kilometers) to the north of the site. The nearest faults mapped with latest Pleistocene to Holocene activity (<15,000 yrs) are the Simi- Santa Rosa fault, and an unnamed fault located about 5.8 miles (9.4 km) southeast of the site associated with the Santa Monica-Hollywood-Raymond system (USGS, 2015). The nearest fault mapped with Pleistocene movement (<130,000 yrs) is the Bailey fault about 2.4 miles (4.4 km) southeast of the site.

Several historic earthquakes have produced relatively strong ground shaking within the vicinity of the project site. Notable examples include the magnitude 6.4, 1933 Long Beach earthquake, the magnitude 6.5, 1971 San Fernando earthquake, the magnitude 5.2, 1972 Point Mugu earthquake, the magnitude 6.0, 1987 Whittier Narrows earthquake, and the magnitude 6.7, 1994 Northridge earthquake.

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3.2 LOCAL GEOLOGIC SETTING

The project site is within the flat topography of the Santa Clara River flood plain, at elevations of about 9 feet above mean sea level. The nearest water course is Rovolon Slough about 1.5 miles east, which flows into Callegaus Creek and drains to the Pacific Ocean about 3 miles to the south of the site. The nearest hills are the Santa Monica Mountains about 2 miles to the southeast of the site.

According to the published geology map for the area (Dibble 1990) the site is underlain by Holocene-age alluvium consisting of “gravel, sand and clay of flatlands” as shown on Figure 3.

The site is mapped as being an area susceptible to earthquake liquefaction by the California Geologic Survey (CGS), formerly known as the California Division of Mines and Geology (CDMG) (CGS, 2002a).

3.3 SUBSURFACE CONDITIONS

Previous borings at the site included five (5) hollow stem auger borings, which extended to maximum depths ranging from 6.5 feet to 8 feet bgs (N&M, 2010). Those borings encountered pavement sections (asphalt concrete 2 to 3 inches thick, over aggregate base 3 to 5.5 inches thick) over young alluvium (medium dense, sandy SILT and clayey SILT soils, with rare thin silty SAND lenses) to the depths explored.

Investigations for this study included five (5) hollow stem auger borings (B-15-001 through B-15-004 and B-17-005). Three borings extended to 5 feet bgs, one boring (B-15-004) extended to 21.5 feet bgs and one boring (B-17-005) extended to 25.5 feet bgs. Details of the field investigations and the boring logs are attached in Appendix A. In summary, the borings undertaken on roadways (B-15-001 through B-15-

003) encountered 3 inches of asphalt over 5 inches of aggregate base above silty SAND (SM), clayey SAND (SC) or poorly-graded SAND (SP) to 5 feet bgs. In borings B-15-004 and B-17-005, where Standard Penetration Test (SPT) testing was undertaken, very loose silty SAND was present to a depth of 5 feet bgs. Below this, very soft SILT (ML), sandy CLAY (CL) and fat CLAY (CH) were present to the bottom of the boring at 25.5 feet bgs.

Soil samples were collected from the borings for laboratory testing as shown in Appendices A and B.

3.4 GROUNDWATER

Groundwater was not encountered in B-15-001 through B-15-003 (depths of 5 feet bgs), but was encountered at a depth of 10 feet bgs in B-15-004 and 24 feet bgs in boring B-17-005. The CGS prepared a Seismic Hazard Report for the Camarillo Quadrangle (CGS, 2002b). Based on a review of this report, the historically highest groundwater levels for the project area are on the order of 6 feet bgs as shown on

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Figure 4. In previous site investigations, groundwater was not encountered to the maximum depths explored of 8 feet bgs, however “wet zones” were observed in two borings at depths of 5 feet bgs and 7 feet bgs, respectively (N&M, 2010). High moisture content was also present in a soil sample collected at 5 feet bgs in B-15-004, which is consistent with historical data. Groundwater levels are likely to vary based on tidal, seasonal and anthropogenic factors.

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4.0 PAVEMENT RECOMMENDATIONS

4.1 SUMMARY OF FINDINGS

The geological, geotechnical, and seismic conditions at the project site have been evaluated in terms of their impact on the proposed project. Based on the findings of this investigation, it is AECOM’s opinion that geologic hazards and geotechnical concerns will not significantly impact the project. The existing pavement sections encountered in the field at the boring locations included asphalt concrete underlain by aggregate base material. A summary of pavement thickness is shown in the table below:

Table 1 Summary of Existing Pavement Sections

Boring No.

Maximum

Depth drilled (feet)

Asphalt Concrete (inches)

Aggregate Base

(inches)

Subgrade Soil Type

B-15-001 5.0 3.0 5.0 Clayey Sand with Silt

B-15-002 5.0 3.0 5.0 Poorly

Graded Sand with Silt

B-15-003 5.0 3.0 5.0 Silty Sand B-1(1) 8.0 2.0 3.0 to 3.5 Sandy Silt B-2(1) 6.5 3.0 4.0 Sandy Silt B-3(1) 6.5 3.0 5.0 Silty Sand B-4(1) 6.5 2.5 5.5 Silty Sand B-5(1) 6.5 2.5 5.0 Silty Sand

Note:

1. Borings performed by Ninyo & Moore in 2010

4.2 SUBGRADE CONDITIONS

The subgrade soils encountered beneath proposed pavement areas are described in the “Subsurface Conditions” section of this report. In general, subgrade soils consist of silty and clayey sands with R-values ranging from 50 to 78. The flexible pavement sections presented in this report were designed using the Air National Guard (ANG) technical letters and technical memoranda that are applicable for this project.

4.3 PAVEMENT DESIGN RECOMMENDATIONS

The existing pavement is more than 20 years old and deteriorated with severe alligator cracking and patched areas. Localized repair or overlay of the existing pavement would not provide a longer-term

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4-2 pavement design life, assumed to be 20 years. Therefore, new pavement structural sections are required for the following areas of the project:

Proposed rehabilitation of Mulcahey Drive and POL Road;

New roadway construction from the proposed vehicle inspection structure to the main gate entrance.

Project specific traffic data is not available at this time. Traffic Design Index (DI) data from previous reports prepared by other consultants indicate a DI value of 5 & 6 was appropriate for the base facility.

Evaluating the traffic index was out of the scope for the current project, therefore the DI values recommended by others were used to provide the pavement structural section. The design of pavement generally conformed to the guidelines provided in Air National Guard/Army/Air Force Engineering Technical Letters (ETL) and Technical Memoranda (TM) that are applicable to this project. The following technical documents were referred to:.

ANG ETL 01-1-1, Section 9 – “Vehicular Pavement and Parking”;

TM 5-822-5/AFM 88-7, Chapter 1 – “Pavement Design for Roads, Walks, and Open Storage Areas”;

TM 5-822-2/AFM 88-7, Chapter 5 – “General Provisions and Geometric Design for Roads, Streets, Walks, and Open Storage Areas”.

4.3.1 Methodology

The methodology and assumptions for the pavement design are as follows:

A Traffic Design Index of 5 and 6 was utilized.

R-value is a measure of resistance of saturated subgrade soil in the vertical direction typically used in California. California Bearing Ratio (CBR) is a penetration test that provides similar characteristics of the soils as the R-value but typically estimates the strength of soil compared to strength of a standard crushed rock with known properties and expressed as a ratio.

The army/air force guidelines typically use CBR for the pavement design. Representative subgrade soil samples were tested for R-value and were converted into an equivalent CBR value using several published correlations. Based on available site specific laboratory test data, a R-value of 50, which correlated to an equivalent CBR value of 12, was implemented in the pavement design calculations.

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A CBR of 80 was assumed for the aggregate base (AB) based on guidelines provided in the Technical Memoranda (TM 5-822-5/AFM 88-7, Chapter 1, Page 6-1).

According to Figure 8-1 in the Technical Memoranda, the minimum required pavement structural section thickness, which includes Asphalt Concrete (AC) and AB, for a Traffic Design Index of 5 and 6 are 9.5 inches and 11 inches, respectively.

For a CBR of 80 for the AB, Table 6-1 states the minimum thicknesses of the AC for a Traffic Design Index of 5 and 6 are 2.5 inches and 3.0 inches, respectively. The minimum thickness of the AB for a Traffic Design Index of 5 and 6 is 4.0 inches.

4.3.2 Reconstruction

The existing pavement structure should be removed and the upper 12 to 14 inches of pavement subgrade should be excavated and re-compacted to at least 95% of the maximum dry density determined per ASTM D1557 prior to placing the new pavement section as specified in section 5.2.2. The recommendations provided in this section are for a 20-year design life flexible pavement consisting of AC over AB. To achieve a 20-year design life, routine maintenance of AC pavements is required. All supporting calculations, tables and charts that were utilized for estimating the pavement section are included in Appendix C. A summary of the recommendations for the pavement section is shown in the table below:

Table 2 Summary of Proposed Pavement Sections

Roadway Traffic Design Index

Recommended Pavement Section

AC (inches) AB (inches) Compacted Subgrade (in)

Pol Road, Mulcahey Drive 5 2.5 7.0 12

Pol Road, Mulcahey Drive 6 3.0 8.0 14

Note:

1. AC = asphalt concrete, AB = aggregate base

4.3.3 Alternative

Based on our experience, an alternative to reconstruction would be full depth rehabilitation (FDR) that provides the same design life at a lower cost. The FDR transforms the existing AC and AB into the base material for the new pavement section. FDR would consist of pulverizing the existing AC and AB sections in-place and mixing into the existing sandy subgrade soils (to a minimum depth of 6 inches into the subbase), adding a small amount of cement (typically 3 to 4 percent) as a stabilizer, and compacting to form a uniform base material. The new AC is then placed on the treated base material. This process eliminated the cost of off hauling old AC and AB and importing new AB.

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5.0 CONSTRUCTION REQUIREMENTS

5.1 MATERIALS AVAILABLE

The majority of the soils at the project site within a depth of 5 feet are expected to consist of silty sand, clayey sand, sandy silt. These materials are suitable for use as general fill provided they are free of organics and vegetation. At deeper depths, the materials are sandy clay and fat clay and are soft in nature.

5.2 GENERAL EARTHWORK REQUIREMENTS

5.2.1 Site Preparation and Earthwork

Prior to earthwork, the areas to be cut, to receive fill, or to receive stockpile materials should be cleared and stripped of all debris, deleterious materials, organics and vegetation. Cleared and grubbed material as well as all rubble waste which may be encountered or created should be removed and disposed of appropriately in accordance with Project Specifications, or the material can be removed and delivered to an approved sanitary landfill under observation of the Engineer.

In areas of cut or fill, the exposed excavated surface should be observed by the Engineer to confirm that satisfactory subgrade soils have been encountered. The bottom of excavation should then be scarified, moisture conditioned to be near the optimum moisture content, and compacted to at least 95 percent relative compaction. Compacted subgrade should be stable prior to placing aggregate base materials.

During construction, if localized areas of expansive soils or R-values less than the design R-values are encountered, additional testing of the soils should be performed under the direction of the Engineer.

Appropriate measures such as removal and/or mixing with stronger soils should be considered.

5.2.2 Compaction

The upper 12 or 14 inches of pavement subgrade (per Table 2) should be compacted to at least 95% of the maximum dry density determined per ASTM D1557, according to TM 5-822-5/AFM 88-7, Chapter 1.

This may be accomplished by first removing the upper 6 or 7 inches of the subgrade soils and then scarifying the exposed ground the remaining 6 or 7 inches. The scarified ground can then be re-compacted in-place, with the upper 6 or 7 inches of soils replaced as compacted fill. Excavated material may be re-used as fill as long as it meets the requirements of Table 4. Adequate testing and observation of fill placement is the responsibility of the Engineer/Contractor.

5.2.3 Demolition

Any existing at-grade or underground drainage structures that interfere with the proposed grading along the alignment, and any foundations, if encountered during grading, should be removed in accordance with the

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5-2 applicable Project Specifications. Additionally, all backfill for such items should be compacted to at least 90 percent relative compaction (per ASTM D1557) unless specified otherwise.

5.2.4 Excavations

Excavations during construction should be performed in accordance with applicable local, state, and federal regulations such that excessive ground movement and failure will not occur. Where space permits and provided that adjacent structures, utility lines, etc. are adequately supported, open excavations may be considered for construction of the project. Unsupported temporary slopes with conditions similar to those encountered during the exploration should be made at an inclination no steeper than 2:1 (horizontal to vertical), or flatter, as field conditions dictate. Trench excavations should be made with nearly vertical sides, using sheeting and shoring whenever required. All excavation should be observed by a competent person as described by Cal OSHA so that any necessary modifications based on variations in soil conditions encountered can be performed in an efficient manner. Soils encountered during our field investigation should be rippable with conventional earthworks equipment. All applicable safety requirements and regulations, including Cal OSHA regulations, should be satisfied.

Surcharge loads from vehicle/equipment parking and traffic or stockpile materials should be set back from the top of the temporary excavation a horizontal distance equal to at least 1.5 times the depth of excavation. Surface drainage should be controlled along the top of temporary excavations to prevent wetting of the soils and erosion of the excavated faces. Even with the implementation of these recommendations, sloughing of the surface of temporary excavations may still occur, and workers should be adequately protected. In any event, excavation and personnel safety during construction is the sole responsibility of the Contractor. If encountered, soft soils or low-density fills should be removed at the direction of the Engineer. Appropriate off-site disposal sites for the removed material shall be at the owner’s and/or contractor’s discretion.

5.2.5 Material Specifications

Aggregate base materials, where applicable, should be Class 2 aggregate base, conforming to Caltrans Standard Specifications with a minimum R-value of 78. The base materials should be brought to uniform moisture content near optimum moisture, and then compacted to at least 95 percent (per ASTM D1557).

5.3 SITE DRAINAGE

The site pavement should be graded and appropriate drainage should be provided to avoid water infiltration into excavations or ponding on pavements. Grades adjacent to excavations should be sloped away from it in all directions and ponding of water in the vicinity of the excavation should not be allowed. Watering of any landscaped areas near proposed excavations should be temporarily suspended

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5-3 until the operation is completed. A site specific storm water management plan is recommended to be developed for the roadway construction operation to ensure water doesn’t adversely impact excavations.

5.4 SPECIFICATIONS

In addition to the items discussed above, the following requirements shall be included in the project specifications:

The subgrade should have a minimum R-value of 50 in asphalt pavement areas to a depth of 3 feet measured from finished grade of the subgrade.

During construction, if localized areas of R-values less than the values noted above are encountered, then additional testing of the native soils should be performed under the direction of the Engineer, Appropriate measures such as removal and/or mixing firm other soils should be considered at the direction of the Engineer.

Prior to placement of pavement sections, the subgrade soils shall be compacted as recommended in Section 5.2.

Extreme care must be taken to ensure moisture-sensitive aggregates are not used for Asphalt Concrete mix design.

For the FDR alternative, the pulverized AC and AB shall be mixed with sub-grade soils to a minimum depth of 6 inches into the sub-grade.

The pulverized AC and AB mixture with soil shall be compacted to at least 95% per ASTM D1557.

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6.0 FOUNDATION RECOMMENDATIONS

6.1 SHALLOW FOUNDATIONS

Shallow foundations are a proposed option for the project site. Shallow foundations can provide adequate support for the proposed structure. Various types of shallow foundations were considered. The spans between the canopy columns would not make a strip footing or slab-on-grade systems feasible. Due to the structure being an open structure, spread footings are deemed the only feasible option.

6.1.1 Spread Footing Foundations

The proposed structure can be supported on spread footings placed on a layer of compacted fill. The spread footing should be a minimum of 2-feet by 2-feet wide and established at a minimum of 2 feet below the finished grade. An allowable bearing pressure of 1,500 pounds per square foot (psf) maybe assumed for the spread footings with the above minimum dimensions. The allowable bearing pressure is a net value. Therefore, the weight of the foundation and the backfill over the foundation to the subgrade level may be neglected when computing dead load. The spread footing will have a permissible settlement up to 1 inch and differential settlement up ½ inch. These settlements are attributed to consolidation of the underlying native soils. The bearing value is for the total of dead and frequently applied live loads, and may be increased by one-third for transient loading conditions, including wind and seismic forces. Uplift load will be counter acted by the weight of the spread footing.

Spread footings were considered to provide support for the proposed structure. However, the bearing, uplift, and lateral capacities for the spread footings would be less than that of deep foundations. Due to the clayey subsurface, a shallow foundation would experience permissible settlements up to 1” as allowed by California Building Code (CBC).

6.1.2 Resistance to Lateral Loads

Resistance to lateral loads may be developed by a combination of friction acting along the base of footings and passive earth pressure developed against the sides of footings below grade. Ultimate passive pressure may be taken as equivalent to the pressure exerted by a fluid weighing 300 pounds per cubic foot (psf/ft) with a maximum value of 1,500 psf. The pressure should be used as a triangular distribution to the allowable limit and then should remain at the maximum limit. The ultimate coefficient of friction between poured-in-place concrete footings and the underlying soils may be taken as 0.30. The passive pressure will be reduced by 1/3 when used in combination with friction resistance of the footing.

6.1.3 Site Preparation and Grading

Prior to the start of construction, the following should be performed:

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All utilities should be located in the field and either rerouted, removed, abandoned, or protected.

Areas to be graded should be stripped of debris (if any), and the material should be removed from the site.

Demolished pavement and concrete should be separated for recycling.

The upper soil should be excavated and replaced with compacted fill as shown. The bottom of the excavation should be:

Scarified to a depth of 8 inches.

Moisture conditioned to above-optimum moisture content.

Compacted to at least 95 percent relative compaction (ASTM D1557).

Where the soils at the bottom of the excavation preclude compaction, they should be excavated to a sufficient depth such that a firm and unyielding surface is achieved at the planned bottom of excavation or the base of fill.

6.1.4 Fill and Backfill

The material excavated from the project site, in the opinion of the Geotechnical Engineer, is not suitable for use in constructing Structural Fill. It is recommended that “Structural Fill” be used within the structural zone of all foundations and floor slabs. The structural zone is defined as the zone within 2 feet below the footing and 2 feet outside the edge of the footing. It is recommended for all footings. Structural Fill shall consist of material imported from an off-site source. Structural fill should meet the gradation requirements in Table 3:

Table 3: Structural Fill Criteria Sieve Size Percentage Passing by Weight

2” 100

1 ½” 95-100

¾” 50-100

3/8” 12-55

No. 4 0-25

No. 8 0-5

No. 200 0-3

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Structural Fill materials shall be free of organic material, debris, or other deleterious materials. Materials greater than 1 inch in size shall be placed so that they are completely surrounded by compacted finer soils. No nesting of rocks shall be permitted. No perishable, spongy, hazardous, or other improper materials shall be used.

Structural Fill materials should have an Expansion Index of 30 or less when tested in the laboratory in accordance with ASTM D 4829.

Fill and backfill should be compacted by:

Placing in loose layers less than 8 inches thick.

Moisture conditioning to above-optimum moisture content.

Compacting to at least 95 percent relative compaction.

Concrete flatwork (i.e. slabs-on-grade, sidewalks, hardscape, curbs, and gutters) should be underlain by a minimum of 12 inches of compacted engineered soil compacted to at least 95 percent relative compaction

(ASTM D1557).

Import materials for fill and select backfill should meet the criteria in Table 4. If retaining/basement walls are considered, select backfill behind those structures should be placed within a horizontal distance of 5 feet or one-half of the wall height, whichever is greater.

Table 4: Import fill and Select Backfill Criteria Criteria Import Fill Select Backfill

Maximum particle size (inches) 3 1

Maximum liquid limit (%) 10 5

Maximum plasticity index (%) 5 0

Maximum percentage passing the No. 200 sieve (%) 40 30

Minimum sand equivalent 20 20

Maximum Expansion Index 30 30

The soils encountered in the borings are not expected to meet the above criteria for select backfill.

However, it is possible to mix on-site soil with new material to meet the gradation for import fill.

Generally, site grading may be accomplished with conventional construction equipment if access is not a concern. The backfill should be compacted using vibratory compactors.

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7.0 CONSTRUCTION CONSIDERATIONS

The contractor should conform to all applicable occupation and health standards, rules, regulations, and orders established by the State of California.

7.1 CONSTRUCTION ADVISORIES

During excavations, erosion and surficial sloughing may occur; excavations during wet seasons will require groundwater dewatering and erosion protection.

7.2 PRECONSTRUCTION SURVEY AND CONSTRUCTION MONITORING

Prior to any site work and excavations, conditions of existing improvements should be surveyed and photo documented.

7.3 CONTAMINATED SOIL CONSIDERATIONS

Because yellow thermoplastic pavement markings and other types or colors of roadway pavement markings may contain lead-based paint, any affected lead-based roadway pavement markings should be collected, tested, and if necessary, transported and disposed of, in accordance with applicable State and federal regulations.

As with any project that involves excavation, there is the potential for unknown hazardous contamination to be encountered during construction. If encountered, contaminated soils should be removed and disposed of properly in accordance with appropriate environmental protocols.

7.4 CUTS AND EXCAVATIONS

Excavation should be performed in accordance with this report. Over-excavation is recommended for foundations of structures within the structural zones of the foundations as defined in Section 6.1.4.

Moisture conditioned structural fill is recommendations within the structural zones. Based on the existing data interpreted from the widely-spaced borings, the design of temporary slopes and benches may assume a Cal/OSHA soil type C. The contractor should verify the Cal/OSHA design soil type during construction and consult with AECOM as necessary.

7.5 TEMPORARY EXCAVATIONS

Temporary unsupported slopes should be observed at regular intervals by a Competent Person as defined by Cal/OSHA to provide a safe and stable slope. Surcharge loads from vehicles and stockpiled material should be kept away from the top of temporary excavations and surface drainage should be controlled to prevent excessive wetting and erosion of excavation faces.

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7.6 SITE DEWATERING AND CONTROL OF WATER DURING CONSTRUCTION

Provisions for adequate surface drainage should be provided to drain water away from excavations, and all excavations should be protected against flooding. Based on the site subsurface explorations, it is unlikely that groundwater will be encountered during construction. However, localized perched water conditions may exist within the subsurface, especially due to the inherent possibility of tidal influence due to close proximity to the ocean. Adequate measures should be in place in order to ensure proper drainage of excavations due to perched water.

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8.0 UNCERTAINTIES AND LIMITATIONS

AECOM has observed only a small portion of the pertinent subsurface conditions at the proposed project site. Conclusions and recommendations presented in this report are based upon the understanding of the project by AECOM and the assumption that the subsurface conditions do not deviate appreciably from those disclosed by the site subsurface exploration. In the event that the locations, configurations, layout, loadings, or features of the proposed excavations are modified, the recommendations presented in this report may not be applicable. It is the responsibility of the Owner to bring any such changes to the proposed excavations as well as any differences between the subsurface conditions described in this report and the subsurface conditions encountered during construction to the attention of the Geotechnical Engineer. In this way, supplemental recommendations, if required, can be made without delay to the project.

Professional judgments presented in this report are based on an evaluation of the technical information gathered and the general experience of AECOM in the practice of geotechnical engineering. AECOM does not guarantee the performance of the project in any respect, only that the engineering work and judgments rendered meet the standard of care of the geotechnical profession at this time. Our recommendations for this project may not be used for other projects.

Any person using this report for bidding or construction purposes should perform such independent investigations as they deem necessary to satisfy themselves as to the surface and subsurface conditions to be encountered and the procedures to be used in the performance of work on this project.

FIGURES

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Oak View

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Casa Conejo

Channel Islands Beach

Channel Islands Beach

Los Padres NF

Santa Monica Mountains NRA

Channel Islands NP

PACIFIC OCEAN

Oxnard Airport

Project Site

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Dec. 2015 Preliminary Geotechnical Report

Regional Geologic Map

Project Site

Source: Tan, Siang, Clahan, Kevin, and Hitchcock, Christopher, 2004, Preliminary Geologic Map of the Camarillo 7.5’ Quadrangle, Ventura County California

EXPLANATION

Qha1 – Alluvium deposits (Holocene) Qht1 – Stream terrace deposits (Holocene) Qhw1– Wash deposits (Holocene) Qhw2 – Wash deposits (Holocene) Qhw3 – Wash deposits (Holocene)

Qw – Active wash deposits with major river channels (Holocene)

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Proposed Roadway Rehabilitation of Mulcahey Drive and Pol Road at

California Air National Guard Base Facility, Channel Islands

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Dec. 2015

Preliminary Geotechnical ReportProposed Roadway Rehabilitation of Mulcahey Drive and Pol Road at

California Air National Guard Base Facility, Channel Islands Historically Highest Ground Water Map

Project Site

Modified from State of California Seismic Hazard Zone Report for The Camarillo 7.5-Minute…