Attach7_Geotechnical_Report.pdf

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Contents Section Page

Acronyms and Abbreviations ......................................................................................................................... V

Introduction ............................................................................................................................................... 1-1

1.1 Background, Purpose and Scope .................................................................................................. 1-1

1.2 Design Code .................................................................................................................................. 1-1

1.3 Limitations .................................................................................................................................... 1-2

Background ................................................................................................................................................ 2-1

2.1 Site and Vicinity General Characteristics ...................................................................................... 2-1

2.2 Project Description ....................................................................................................................... 2-1

Technical Data ........................................................................................................................................... 3-1

3.1 Geotechnical Field Exploration Program ...................................................................................... 3-1

3.1.1 Borings and Test Pits ....................................................................................................... 3-1

3.1.2 Percolation Testing .......................................................................................................... 3-2

3.2 Laboratory Testing ........................................................................................................................ 3-2

3.2.1 California Bearing Ratio ................................................................................................... 3-2

3.2.2 CU Triaxial Shear Test ...................................................................................................... 3-3

3.2.3 Consolidation Test ........................................................................................................... 3-3

3.2.4 Soil Index and Classification Tests ................................................................................... 3-4

Engineering Evaluation and Interpretation .................................................................................................. 4-1

4.1 Subsurface Conditions .................................................................................................................. 4-1

4.2 Groundwater Conditions .............................................................................................................. 4-1

4.3 Corrosion Potential ....................................................................................................................... 4-1

4.4 Foundation Recommendations .................................................................................................... 4-2

4.4.1 Bearing Capacity .............................................................................................................. 4-2

4.4.2 Coefficient of Friction ...................................................................................................... 4-2

4.4.3 Settlement ....................................................................................................................... 4-3

4.5 Lateral Earth Pressures ................................................................................................................. 4-3

4.6 Seismicity and Seismic Hazards .................................................................................................... 4-4

4.6.1 Seismic Parameters ...................................................................................................... 4-4

4.6.2 Seismic Hazard Assessment (Liquefaction) .............................................................. 4-5

Construction Considerations and Recommendations ................................................................................... 5-1

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

5.1.1 Site Preparation ............................................................................................................... 5-1

5.1.2 Excavation ....................................................................................................................... 5-1

5.1.3 Subgrade Preparation and Testing .................................................................................. 5-2

5.1.4 Reuse of Onsite Material ................................................................................................. 5-2

5.1.5 Grading and Drainage ...................................................................................................... 5-2

5.2 Quality Control Testing ................................................................................................................. 5-2

5.3 Corrosion Considerations ............................................................................................................. 5-3

References ................................................................................................................................................. 6-1

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Appendix A - Geotechnical Drilling and Testing Investigation Report (TTL Associates, 2017) ......................... 7-2

Appendix B – Field Percolation Test Report (TTL Associates 2019) ............................................................... 7-3

Appendix C – Civil Key Map ........................................................................................................................ 8-4

Appendixes

A Geotechnical Drilling and Testing Investigation Report (TTL Associates, 2017) B Percolation Testing (TTL Associates, 2019) C Civil Key Map Tables

Table 3-1. Summary of Borings .............................................................................................................................. 3-1

Table 3-5. Summary of Laboratory CBR Test Results ............................................................................................. 3-2

Table 3-8. Summary of Laboratory Triaxial Shear Test Results .............................................................................. 3-3

Table 3-9. Summary of Laboratory Triaxial Shear Test Results .............................................................................. 3-3

Table 4-7. Foundation Recommendations – Allowable Bearing Capacity.............................................................. 4-2

Table 4-8. Foundation Recommendations – Coefficients of Base Friction ............................................................ 4-2

Table 4-10. Lateral Earth Pressure Recommendations .......................................................................................... 4-3

Table 4-11. Seismic Design Parameters for Return Period of 2,475 Years ............................................................. 4-5

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Acronyms and Abbreviations ϕ' effective friction angle

ACTS Advanced Construction Technology Services

ASCE American Society of Civil Engineers

ASTM American Society for Testing and Materials bgs below ground surface bpf blows per foot

CBR California Bearing Ratio

CH2M CH2M HILL, Inc.

cm centimeter g ground acceleration

H:V Horizontal to Vertical

IBC International Building Code in inch kg kilogram km kilometer kN kiloNewton kPa kilopascal ksf thousand square feet ksi kips per square inch

LL Liquid Limit m2 square meter mm millimeter

MPa megaPascal

NA not applicable pcf pound per cubic feet

PGA Peak Ground Acceleration

PI Plasticity Index

PL Plastic Limit ppm parts per million

SPT standard penetration test

TP test pit

UCS unconfined compressive strength

UFC Unified Facilities Criteria

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UFGS Unified Facilities Guide Specifications

USCS Unified Soil Classification System

WN Natural Moisture Content

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SECTION 1

Introduction CH2M HILL, Inc. (CH2M) has been retained by the Ohio Air National Guard, 179th Airlift Wing to complete geotechnical explorations, geotechnical analysis, and develop a geotechnical report for design of a new 24,000 sf firestation at Mansfield, Lahm Airport, Ohio. The geotechnical report is required for the conceptual development of designs for the firestation facilities that are planned. This report summarizes CH2M’s understanding of proposed design facilities, and documents the geotechnical evaluation and design considerations for the planned facility.

1.1 Background, Purpose and Scope

Geotechnical explorations and associated laboratory testing were completed to investigate subsurface conditions at the Mansfield firestation site by in January 2017. The information obtained from the explorations, field tests, and laboratory testing have been summarized in a Geotechnical Drilling and Testing Investigation report prepared for the project by TTL Associates, under contract to CH2M (TTL, 2017), provided as Appendix A of the Basis of Design volume.

The scope of work consisted of the following activities:

• Conducting geotechnical field explorations at the site and performing laboratory testing on representative samples collected from the field explorations.

• Reviewing the soil borings, soil test pits, and laboratory analyses presented in the Geotechnical Drilling and Testing Investigation Report (TTL, 2017), provided as Appendix A of the Basis of Design volume.

• Conducting geotechnical analyses for the site and proposed facility.

• Developing recommendations for design and construction.

• Preparing this geotechnical design and recommendations report.

1.2 Design Code

The project specific recommendations contained herein are provided in general accordance with applicable Unified Facilities Criteria (UFC), International Building Code (IBC) and Unified Facilities Guide Specifications (UFGS) guidelines.

UFC requirements are considered guidance and best practices and can assist designers in identifying functional requirements of building systems and spaces.

For applying best practices for earthwork of semi-permanent construction, the guidance in UFC 3-201-01, Civil Engineering Change 1, and UFC-3-220-01, Geotechnical Engineering, were used as applicable guidelines in this report.

A firestation is considered a critical facility per the IBC, and depending on subsurface conditions may require a site-specific (dynamic) seismic hazard analysis. However, considering generally favorable subsurface conditions and according to UFC 3-310-04, the risk category is modified, falling under risk category IV. Therefore, in accordance with the UFC guidelines, a site-specific seismic evaluation is not required and the design can be performed using the seismic design parameters specified in the IBC and UFC.

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1.3 Limitations

This report has been prepared for the exclusive use of the Ohio Air National Guard, the US Air Force, and CH2M, for specific application to the proposed firestation facilities as described in this report at the Mansfield project site. It has been prepared in accordance with generally-accepted geotechnical engineering practice. No other warranty, expressly or implied, is made.

The analyses, interpretations, and recommendations contained in this report are based on data obtained during the January 2017 geotechnical field exploration, results from subsequent laboratory testing, and from preliminary facility information. The facility information provided included the approximate area of the firestation, and limited ancillary facilities supporting the firestation. Specific loadings, foundation elevations and types, traffic use, and bearing pressures were not provided at the time of the investigation; however, it is understood that the facility is to be located at or near existing grade, with conventional shallow foundation systems and with maximum ground pressures less than approximately 1,500 pounds per square foot. The evaluations and recommendations contained herein were developed using guidance from applicable standards including UFC and international codes. It may be necessary to modify the recommendations provided in this report for application to the specific project and contracting requirements.

This report does not reflect variations that may occur between borings and test pits, or because of the modifying effects of construction or weather, and does not include evaluation of areas at the site not explored. The nature and extent of such variations may not become apparent until or after construction. If variations appear, CH2M should be immediately notified so that further evaluation and supplemental recommendations can be provided.

The Scope of Work for this project does not include evaluation of environmental or biological conditions of the site and does not identify pollutants or hazardous materials or conditions.

CH2M is not responsible for any claims, damages, or liability associated with interpretation of subsurface data or for reuse of subsurface data without CH2M’s express written authorization. If changes in the nature, design, or location of the project as outlined in this report are made, the conclusions and recommendations contained in this report will not be considered valid unless CH2M reviews the changes and either verifies or modifies the conclusions of this report in writing.

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SECTION 2

Background

2.1 Site and Vicinity General Characteristics

The proposed firestation location is immediately east of the existing Building 102 Hangar at approximate elevation 1295 feet. The site currently is paved and serves as a parking area for surrounding facilities. The topography is generally flat.

It is our understanding that existing facilities are generally performing well, with no indicate of distress to the structures from poor foundation conditions, poor pavement designs, or unexpected wear conditions. As-built drawings, existing pavement section details, and previous earthwork records were not available; therefore, a proper assessment of the performance of existing facilities or underlying subgrade related to the facilities cannot be made.

2.2 Project Description

The project involves development of a new 24,000 square foot firestation to support the airport and nearby facilities.

The location of the proposed structures are shown in the Civil site plans within the design drawings. The location of exploratory borings and test pits in relation to the location of final design facilities are shown schematically in Appendix B, Civil Key Map. It is anticipated that because of the relatively favorable subsurface conditions, it is assumed that foundation system will consist of conventional, shallow footings and/or slabs, pavements, pads, and structural walls and interior columns.

It is anticipated that the site grading will be limited to minor cuts and fills and that significant cut or fill slopes will not be required. Additionally, it is assumed that high retaining walls or significant below grade structures will not be required at the site.

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SECTION 3

Technical Data This section presents a summary of field tests and subsurface explorations program completed for the project and a discussion of laboratory testing completed. Technical data collected during the geotechnical field exploration and associated laboratory testing program is provided.

Additional detailed descriptions of the geotechnical field explorations and field and laboratory testing, along with the results from each, are provided in a Geotechnical Drilling and Testing Investigation Report prepared by TTL Associates of Toledo, Ohio .CH2M subcontracted TTL Associates to work onsite to provide equipment and laborers to complete the geotechnical field exploration program, observe geotechnical field explorations, collect representative soil samples, and complete laboratory testing. The Geotechnical Drilling and Testing Investigation Report prepared by TTL Associates (2017), including boring and test pit logs for the geotechnical explorations completed for the project is provided as Appendix A of the Basis of Design volume.

3.1 Geotechnical Field Exploration Program

The geotechnical field exploration program was conducted between January 17 and January 24, 2017 and consisted of advancing seven geotechnical borings and five shallow test pits within the footprint of the firestation and nearby area. Borings were advanced to depths of between 35 and 100 feet in general compliance with IBC and UFC requirements. Test pits were excavated to approximately 1-foot depth, to collect shallow bulk samples for testing moisture-density relationship and CBR. The depth of test pit was limited to the extent to that which could be dug with hand tools and whether dense granular material was encountered.

The horizontal location of the elevations of the borings were determined using handheld gps devices with accuracy within 1 meter. The boring designation, ground surface elevation, and termination depth are summarized in Table 3-1.

Table 3-1. Summary of Borings

Boring Number Boring Elevation (FT-

NAD83))

Test Pits Termination

Depth (ft)

B-1 1296.19 35 B-2 1296.16 35 B-3 129538 35 B-4 1295.07 35 B-5 1295.95 35 B -6 1295.92 100 B-7 Not recorded 85

3.1.1 Borings and Test Pits

The boring and test pits were advanced by TTL Associates using mud rotary drilling techniques. The drill rig used to advance the borings was a truck-mounted drill rig.

Soil samples were collected from the borings using a standard 2-inch-outside-diameter, split-spoon sampler in accordance with the American Society for Testing and Materials (ASTM) D1586, Standard Test Method for Standard Penetration Test (SPT) and Split-Barrel Sampling of Soils. This test is used to characterize the consistency of fine-grained soil or the relative density of coarse-grained soil by measuring penetration resistance expressed as blow counts or N-value. The blow count is the number of blows required to advance the standard

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split-spoon sampler 6 inches using a 140-pound hammer falling 30 inches. The sampler is driven down 18 inches and the blow count is recorded for each 6-inch increment. The sum of the blow counts for the second and third increments is referred to as the N-value in blows per 1 foot, denoted as blows per foot (bpf). Low N-values indicate soft or loose soil, where high N-values can indicate hard or dense materials. After the sampler is driven and the blow counts are recorded, the sampler is withdrawn from the borehole to recover the disturbed soil sample.

Soil samples recovered from the borings in the form of disturbed samples were classified and placed in sealable jars.

Bulk soil samples were collected from the test pits which provided adequate sample volume to perform the required laboratory testing.

Sampling intervals and field classifications of soil samples were recorded on the soil boring logs and on the test pit logs presented in the Geotechnical Drilling and Testing Investigation Report (TTL Associates, 2017), provided as Appendix A of the Basis of Design volume.

3.1.2 Percolation Testing

In 2019 CH2M was requested to have onsite percolation tests performed to facilitated design of stormwater management facilities. TTL Associates was procured and performed two percolation tests on June 25, 2019. The results of the percolation tests are included in Appendix B.

3.2 Laboratory Testing

Laboratory testing on representative samples of soil were performed by TTL Associates. The objective of the laboratory testing was to measure CBR, consolidations, soil and index properties, soil strength, and properties related to corrosion potential of soil encountered at the site. Testing was performed in accordance with ASTM standards.

3.2.1 California Bearing Ratio

Three CBR tests were conducted in the laboratory in general accordance with ASTM D1883, Standard Test Method for California Bearing Ratio (CBR) of Laboratory-Compacted Soils.

Results of three tests showed equivalent CBR values for the 0.1 inch and 0.2-inch penetrations, which were essentially the same for each penetration

Table 3-5 summarizes the results of the CBR tests. Additional details on the results of the CBR tests are summarized in the CBR laboratory test plots and test data sheets in Appendix A of the Basis of Design volume.

Table 3-5. Summary of Laboratory CBR Test Results CBR Tests Results

Sample Number/depth (ft)

Moisture Content

Maximum Dry Density Swell CBR (%)

USCS Classification (%) (pcf) (%) at 0.1 in at 0.2 in

B-2/B-4 Composite (1.0) 10.2 127.9 -0.7 5 4.9 Lean Clay with Gravel (CL)

TP-2 (1.0) 17.3 109.3 0.3 3.7 3.6 Lean Clay with Sand(CL)

TP-4 (1.0) 21.3 100.2 0.4 2.8 2.8 Lean Clay with Sand (CL)

Notes:

All CBR specimens were tested after soaking for 96 hours (per the ASTM Test Standard).

Minus Swell Value (-) indicates consolidation.

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Table 3-5. Summary of Laboratory CBR Test Results CBR Tests Results

Sample Number/depth (ft)

Moisture Content

Maximum Dry Density Swell CBR (%)

USCS Classification (%) (pcf) (%) at 0.1 in at 0.2 in

Surcharge weight of 10 pounds was used for all CBR specimens (for soaking and testing). in = inch

3.2.2 CU Triaxial Shear Test

Three triaxial shear strength tests were performed in accordance with ASTM D 4767. The summary of the results is provided in Table 3-8. More detailed results and figures are provided in Appendix A of the Basis of Design volume.

The triaxial shear strength tests were carried out on undisturbed tube samples.

The effective and total shear strength values determined from these tests are summarized in Table 3-8.

Table 3-8. Summary of Laboratory Triaxial Shear Test Results Triaxial Shear Strength Tests Results

Test Pits, Depth (ft)

Total Stress Effective Stress

USCS Classification C, psi Φ (degrees) C, psi ϕ' (degrees)

B-1a/ST-3 (18-20) 4.5 33.6 0.5 36.0 Lean Clay with Sand (CL)

B-4/ST-1 (8-10) 8.0 31.0 0.0 32.0 Lean Clay with Sand (CL)

B-6/ST-1 (18-20) 3.0 23.0 0.0 31.0 Lean Clay with Sand (CL)

Note:

ϕ' = effective friction angle

3.2.3 Consolidation Test

Three consolidation tests were performed in accordance with ASTM D 2435. The summary of the results is provided in Table 3-9. More detailed results and figures are provided in Appendix A of the Basis of Design volume.

The consolidation tests were carried out on undisturbed tube samples.

The compression and recompression index values determined from these tests are summarized in Table 3-8.

Table 3-9. Summary of Laboratory Triaxial Shear Test Results Triaxial Shear Strength Tests Results Compression Index Recompression Index USCS Classification

B-1a/ST-2 (11-13) 0.09 0.018 Lean Clay with Sand (CL)

B-2/ST-2 1(18-20) 0.069 0.012 Lean Clay with Sand (CL)

B-5/ST-1 (8-10) 0.096 0.022 Lean Clay with Sand (CL)

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3.2.4 Soil Index and Classification Tests

Laboratory tests were performed on select soil samples to verify field classifications. The laboratory program consisted mainly of Atterberg limits tests, grain-size analyses, and moisture content tests. Detailed tabulation of results are provided in Appendix A of the Basis of Design volume. Testing was completed in accordance with the following testing standards:

• ASTM D2216, Standard Test Methods for Laboratory Determination of Water (Moisture) Content of Soil and Rock by Mass

• ASTM D422, Standard Test Method for Particle-Size Analysis of Soils

• ASTM D4318, Standard Test Methods for Liquid Limit, Plastic Limit, and Plasticity Index of Soils

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SECTION 4

Engineering Evaluation and Interpretation

4.1 Subsurface Conditions

Generalized subsurface conditions were developed based on soil borings, test pits, and field and laboratory testing performed during the project specific subsurface exploration. The subsurface conditions at the site generally consists of three primary layers.

1. The uppermost layer within the upper 2 to 3 feet consist of undocumented fill composed of lean clay with sand, slag (gravel) and wood fragments. This material is generally firm to stiff with SPT N-values ranging from 5 to 13 blows per foot.

2. The upper native soil layer consisted generally of stiff to very stiff lean clay with sand with SPT N-value ranging from 9 to 30 and pocket penetrometer readings from 2000 psf to over 9000 psf. Interbedded sandy soils were encountered between approximately 20 and 30 feet below ground surface that were loose to medium dense with N-values ranging from 6 to 27 bpf.

3. The lower native soil layer was encountered in borings B-6 and B-7 at depths of 64 feet and 48 feet respectively consisted generally of hard gray lean clay (SHALE). This material was encountered to the total depth of the two borings.

Additional descriptions of subsurface materials encountered are included in the boring and test pit logs in the Geotechnical Drilling and Testing Investigation report (TTL Associates, 2017), provided as Appendix A of the Basis of Design volume.

4.2 Groundwater Conditions

Groundwater was encountered each of the completed borings at the site and varied from approximate depth between 5.7 and 21.4 feet below the ground surface. For general structure excavation, groundwater is not expected to be encountered in significant quantity. However, for vaults, manholes, and relatively deep utility trenches groundwater is likely to be encountered. I inflow of water, if properly managed is not expected to be excessive due to the relatively fine-grain characteristics of the native soil.

4.3 Corrosion Potential

The potential rate of corrosion of steel increases with decreasing soil resistivity. Per UFC 3-570-02A, Cathodic Protection, soil having a resistivity between 2,000 ohm-cm to 10,000 ohm-cm has moderate to severe corrosivity to steel, while soil having a resistivity between 0 and 2,000 ohm-cm has severe corrosivity to steel. The laboratory resistivity tests ranged from 1,220 ohm-cm to 1,805 ohm-cm indicating a severe corrosion to steel.

Chloride content at the site was undetectable and Sulfate Content ranged from 45 to 130 mg/kg. It is industry practice to consider ground with Sulfate concentrations greater than 2,000 mg/kg or Chloride content more than 500 mg/kg to be corrosive for steel and concrete. Therefore, for exposure to chloride and sulfate from the native soil is not expected to be a severe corrosion contributor to steel or concrete.

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4.4 Foundation Recommendations

Based on the conditions observed during the January 2017 Geotechnical Field Exploration Program and subsequent laboratory testing, it is anticipated that proposed structures can be founded on shallow spread or strip foundations providing proper removal of surficial fill soil is performed and proper preparation of subgrade are performed as outlined in this report.

4.4.1 Bearing Capacity

Terzaghi bearing capacity equations (Terzaghi, 1943) were used to estimate ultimate bearing capacity at the site based on footing dimensions, shear strength parameters, and slope inclination factors.

Limited information about the proposed structures or foundations was available as design is currently at a preliminary stage. Some assumptions were made so that recommendations for bearing capacity can be provided.

The ultimate bearing capacity of the spread footing was estimated assuming a minimum footing width of 1.5 feet. Shear strength parameters of the soil were estimated from the results of triaxial shear tests as well as SPT and pocket penetrometer testing.

Allowable bearing capacity is calculated using a factor or safety of 3.0 (allowable bearing capacity = ultimate bearing capacity / 3.0). No assessment was performed for the overturning or uplift of structure footings or for deep foundations (such as piles or shafts). It should be noted that the allowable bearing capacity for the minimum size footing is controlled by the estimated corresponding long-term settlement which is discussed in subsequent sections.

It is recommended that a more detailed bearing capacity analysis be performed prior to submittal of final design documents and be included in a final geotechnical design report.

Table 4-7. Foundation Recommendations – Allowable Bearing Capacity Allowable Bearing Capacity

Bearing Layer Foundation Depth

(feet) Allowable Bearing Capacity for

Square Footing

Lean Clay with Sand 1.5 3000 psf

4.4.2 Coefficient of Friction

Sliding resistance along the bottom of the proposed structures should be calculated using the coefficients of friction presented in Table 4-8. In addition, when base friction is used in conjunction with passive lateral earth pressure to resist sliding forces, a reduced passive earth pressure on the order of two-thirds should be used to account for the strain incompatibility between the two friction mechanisms. Base friction resistance is mobilized at small (less than 0.25 inch) displacements and passive earth pressure is mobilized at large displacements typically unacceptable for most designs.

Table 4-8. Foundation Recommendations – Coefficients of Base Friction Coefficients of Base Friction

Sliding Interface Coefficient of Friction, tan (δ)

Poured concrete on compacted granular fill 0.55

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4.4.3 Settlement

Geotechnical information from the site subsurface explorations was used to evaluate the general settlement of an isolated footing, assuming rigid (non-elastic) structure conditions and non-eccentric loading of the footings for an assumed loading case. A 5 foot foot-by-5 foot footing was assumed for this analysis located at 1.5-foot depth for loading on soil.

Consolidation data from the Geotechnical Drilling and Test Investigation Report (TTL, 2017) was used to estimate the general settlement of an isolated footing. The computer program Settle 3D and Slide by Rocscience was used to calculate the predicted total settlement from footing loads.

The geotechnical data analyses were performed assuming a footing founded on undisturbed native stiff lean clay with a compacted leveling course of granular fill. Specific footing loads, required to perform a detailed settlement analysis, are unknown. However, for the purpose of this general analysis, it was assumed that the maximum allowable bearing pressure of 1,500 psf would be exerted on the footing.

The results of this preliminary analysis indicated that estimated settlement for foundation bearing on the soil is expected to be less than 1.0 inches, with differential settlement estimated to range from 50 % to 100% of the estimated total settlement.

It is recommended that a more detailed settlement analysis be performed prior to submittal of final design documents and be included in a final geotechnical design report.

4.5 Lateral Earth Pressures

The ultimate lateral earth pressures coefficients provided in Table 4-10 may be used for the design of shallow foundations subject to static lateral loading, and for relatively small, less than 10 feet-tall, unrestrained rigid retaining walls (gravity and cantilevered for example). The recommended lateral earth pressure coefficients are suitable for unsaturated soils, level backfill behind and in front of retaining walls, and properly compacted imported granular backfill. Lateral earth pressure coefficients are provided for dense, granular fill material that should be utilized as backfill against retaining walls. Native fine-grained soils should not be used as backfill against retaining wall. If larger or more sensitive retaining structures are planned, specific geotechnical explorations and analysis should be required for the design of the facilities.

Table 4-10. Lateral Earth Pressure Recommendations Recommended Soil Parameters for use in Below-grade Wall Analyses

State of Stress Earth Pressure Coefficient Equivalent Fluid Pressure (pcf ft)

At rest Ko = 0.43 55*H

Active Ka = 0.27 35*H

Passive Kp = 3.69 240*H (reduced for movement)

Notes:

1. The magnitude of lateral earth pressure at a given height of wall is presented in units of pcf per foot of wall height (H). The wall height is the distance between the ground surface and the base of the wall. Walls should be designed to resist surcharge loads and adjacent at-grade structures. The lateral earth pressure caused by a uniform surcharge load is equal to the anticipated surcharge load multiplied by the applicable earth pressure coefficient Ko, Ka, or Kp.

2. Substantial movement must take place before the available passive pressure is mobilized. Therefore, a reduced value of passive pressure one-third to one-half of the total passive pressure should be used when calculating resistance to thrust or sliding. The reduced value will depend on the amount of movement allowed by the structural designer.

3. Equivalent fluid pressures were calculated for granular fill using an estimated moist unit weight of 130 pcf and an angle of internal friction of 35 degrees.

4. For drained earth pressures given to be used for design, provisions for adequate drainage behind the wall must be included for all service-life conditions of the structure.

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Table 4-10. Lateral Earth Pressure Recommendations Recommended Soil Parameters for use in Below-grade Wall Analyses

State of Stress Earth Pressure Coefficient Equivalent Fluid Pressure (pcf ft)

5. Compaction within 6 feet of the concrete walls should be performed with lightweight, hand-operated equipment so that compaction-induced lateral stresses are limited. If heavy or large equipment is used for compaction immediately adjacent to the structure, lateral stresses will be larger than those shown in this table.

H:V = Horizontal to Vertical NA = not applicable

Measures should be taken so that moisture does not build up behind retaining walls. Retaining walls should be provided with drainage to minimize the possibility of unbalanced hydrostatic pressures.

The magnitude of earth pressure on below-grade structures and permanent walls can be influenced by the following:

• Amount of wall movement

• Sequence of construction

• Backfilling methods and materials

• Groundwater level

• Presence of surcharge loads

• Presence of earthquakes or other dynamic forces

Active pressures are used where the top of the wall is permitted to move away from the backfill and the backfill has sufficient strength to resist creep and reconsolidation (for example, crushed rock backfill). The values provided herein are commonly considered typical amounts of wall movement necessary to develop full active and passive earth pressures, respectively.

Movement to Mobilize Full Active Earth Pressure

Soil and Condition Amount of Movement at Top of Wall

Cohesionless, Dense 0.001 to 0.002H

Cohesionless, Loose 0.002 to 0.004H

Note:

Where H is the height of the wall.

Movement to Mobilize Full Passive Earth Pressure

Soil and Condition Amount of Movement at Top of Wall

Cohesionless, Dense 0.01 to 0.02H

Cohesionless, Loose 0.02 to 0.04H

Where H is the height of the wall.

4.6 Seismicity and Seismic Hazards

4.6.1 Seismic Parameters

Structural design of semi-permanent structures is to be completed in accordance with the International Building Code (IBC) 2009 edition as modified by UFC 3-301-01 and UFC 3-310-04. Accordingly, seismic design parameters for the two percent chance of exceedance are provided for use in design, which corresponds to a return interval of 2,475 years.

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Table 4-11. Seismic Design Parameters for Return Period of 2,475 Years

Sources (IBC/UFC 3-301-01)a

0.2 second Spectral Acceleration (g) - Ss 0.119

1 second Spectral Acceleration (g) – S1 0.56

Design 0.2 second Spectral Acceleration(g)-SDs 0.127

Design 1 second Spectral Acceleration(g)-SD1 0.089

Notes:

a 2010 version of UFC-3-301-01.

g = ground acceleration

4.6.2 Seismic Hazard Assessment (Liquefaction)

Liquefaction refers to the loss of shear strength that loose saturated soil deposits can experience during earthquake loading. Cyclic liquefaction occurs when pore pressures within soil increase to the point where the effective stress in the soil approaches zero. When the effective stress in the soil approaches zero, the shear strength of the soil decreases and permanent deformations within the soil can occur. The susceptibility of a soil deposit to liquefaction is a function of the degree of saturation, soil grain size, relative density, percent fines, age of deposit, plasticity of fines, earthquake ground motion characteristics, and several other factors. Liquefaction can significantly affect both settlement and slope stability; therefore, a general assessment of the liquefaction potential at the site was made.

Because of a relatively loose to medium dens silty sand layer that was observed between approximately 15 and 20 feet below ground surface, a liquefaction analysis was performed. This analysis used the computer program LiquefyPro, by CivilTech Software which calculates the cyclic stress ratios in order to determine the factor of safety of the occurrence of liquefaction and determines the strain, or dynamic ground settlement, that is estimated to occur.

Based on the soil type and estimated density of the material encountered during the geotechnical explorations for the project, the site was classified as a Soil Profile Type SD.

Based on our liquefaction analyses, it appears there is a low risk of liquefaction occurring during a 2,500 year earthquake occurrence. The dynamic settlement that was evaluated indicated that no seismic induced settlement would occur, due to the relatively low ground acceleration (PGA) and relatively low earthquake magnitude.

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SECTION 5

Construction Considerations and Recommendations This section presents a discussion of important geotechnical considerations earthwork and construction procedures

5.1 Site Preparation and Earthwork

The following sections include recommendations and design considerations for site preparation, excavation, subgrade preparation, and placement of engineered fills for the project. All earthwork for the project should comply with Division 31, Section 31 00 00 Earthwork of the Unified Facilities Guide Specifications (UFGS) Earthwork activities should be observed by a qualified engineer who is experienced with earthwork and local construction practices, and is familiar with the field explorations, analysis, and design for the facility. The evaluation of suitable earthwork activities should include observation and testing of subgrades, engineered fill, foundation bearing layers, and other geotechnical conditions exposed during the construction of the project.

5.1.1 Site Preparation

Before placement of any fill material in any area, the area should be cleared, grubbed and stripped of all organic material, topsoil, pavements, or material that is soft, saturated, or otherwise considered unstable or unsuitable as subgrade material. Brush, grass, and other ground cover within the proposed structures or paving areas should be cleared and removed. Debris, soil piles, windblown sand, and other deleterious materials should also be removed.

A minimum of 1.5 feet of surface soils should be removed from all areas to receive fill, or where pavement or facilities are to be constructed. In addition, unsuitable material, including unsuitable soil, vegetation, debris, perishable material, or materials should be removed beneath proposed buildings, pavements, and flatwork.

Exposed surfaces should be free of mounds and depressions which could prevent uniform placement of fill and/or compaction. Where fill is to be placed, the site should be initially graded to create a relatively level surface to receive fill, and to provide for a relatively uniform thickness of fill beneath the proposed building structures.

Removal of unsuitable soils should be conducted in the presence of an experienced engineer or construction manager knowledgeable about classification and identification of soil materials. After rough grading has been completed and before further earthwork, the exposed surface should be visually inspected by a geotechnical engineer to verify removal of all unsuitable soils. The geotechnical engineer should also observe proof-rolling of the exposed surface to identify the presence of soft, loose, or otherwise unsound conditions.

Other requirements for site preparation can be found in UFGS 31 00 00 Earthwork.

5.1.2 Excavation

It is anticipated that shallow excavations for the proposed construction can be accomplished using conventional construction equipment.

Excavation of undocumented fill in the upper 1.5 feet should be performed to remove slag, wood and vegetation debris or other man-made materials.

Trench excavations should be made in accordance with local safety regulations and Occupational Safety & Health Administration Health and Safety Standards for Excavations, 29 Code of Federal Regulations Part 1926.

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Temporary earth retention systems may be required to where excavation depths exceed 4 feet. Groundwater was not encountered during the geotechnical field exploration performed at the site.

5.1.3 Subgrade Preparation and Testing

As previously indicated, the upper undocumented fill including wood or vegetation material shall be removed in all areas beneath foundations, pavement, and flatwork. Exposed subgrade beneath roads, pavement, sidewalks, hard shoulders, and other facilities other than buildings should be visually examined by a geotechnical engineer experienced with earthwork and local construction practices to identify problem soils or conditions different than those described in this report. In areas where suitable soil is present at the subgrade level, the upper 1 foot should be moisture conditioned to achieve a moisture content no less than two percent dry of optimum moisture content and compacted to a minimum relative compaction of 95 percent of the maximum dry density in accordance with ASTM D1557. Higher compaction criteria may be required for some facilities. Beneath building foundations. All subgrade preparations should be performed in accordance with guidance in UFC 3-250- 01 Chapter 5 and UFC 3-260-02 Chapter 6 and accompanying guide specifications.

Any areas of the proposed facilities that are settlement sensitive, results of a plate-load test completed on prepared dense soil in accordance with the local practice and ASTM D1196 may be used as an additional means to determination the acceptability of building foundations. If this method is used for quality control purposes, it is recommended that a maximum allowable plate settlement of 10 mm should be considered for an applied pressure equal to twice the allowable bearing pressure.

Final acceptance of subgrade preparation shall be determined by the geotechnical engineer having experience with earthwork and local construction practices.

5.1.4 Reuse of Onsite Material

Native lean clay soil containing less than 5 percent organics content, is suitable material for reuse onsite as general site grading and trench backfill above pipe zones; however it should not be used for fill under pavements, structures, footings, or mat foundations.

5.1.5 Grading and Drainage

All grading must provide for effective drainage away from the buildings, structures, and paved areas during and after construction.

Final grading should include minimum slopes of five percent away from buildings and structures for a distance of at least 10 feet beyond the perimeter of the buildings and airfield pavements. Grades around structures and airfield pavements should be verified after construction and periodically throughout thereafter, and adjusted as a necessary as part of the facility maintenance program. It is recommended that finished floor elevations be established at a minimum of 6 inches above the finish grade at the perimeter of each building.

Joints in paving and flatwork and joints between structures and concrete or asphalt pavement should be sealed and the joints maintained to prevent surface water infiltration.

5.2 Quality Control Testing

All quality control testing should be conducted in accordance with the requirements of UFGS Section 31 00 00 Earthwork, IBC (as modified by UFC), as applicable.

Data and observations should be used by the Contracting Officer to validate the required number of compaction passes for the compaction equipment utilized by the contractor, or relative compaction requirements.

Additional details of developing a test fill program are provided in UFGS 32 11 10 – Drainage Layer.

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5.3 Corrosion Considerations

The field resistivity, chloride and sulfate results show the potential for high to severe corrosivity for steel. The results should be used to assist others in determining the type and degree of corrosion protection that may be required. CH2M recommends that a certified corrosion specialist be consulted to assist with the specific needs of the project.

Design for corrosion considerations and protection of reinforcement and concrete should follow the guidance of ACI, 318, Building Code Requirements for Structural Concrete and Commentary, and ACI 222R, Guide to Design and Construction Practices to Mitigate Corrosion of Reinforcement in Concrete Structures.

Design of steel utilities and steel reinforcing for concrete should also consider the potential rate of corrosion of steel because of the relatively low soil resistivity measured during the laboratory testing.

The concrete grade, cementitious type, and maximum water to cementitious ratio and minimum concrete cover should be selected in accordance with applicable durability requirements. Design of foundations and concrete structures should also consider guidelines and recommendations provided in Chapter 4 (Durability Requirement) of Building Code Requirements for Structural Concrete (ACI 318) by American Concrete Institute (2014).

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SECTION 6

References American Concrete Institute. 2014. Building Code Requirements for Structural Concrete and Commentary. ACI 318-14.

American Concrete Institute. 2011. Guide to Design and Construction Practices to Mitigate Corrosion of Reinforcement in Concrete Structures. ACI 222R.

American Concrete Institute. 1988. Suggested Analysis and Design Procedures for Combined Footings and Mats.

ACI 226.2R. Reapproved 2002.

American Society of Civil Engineers (ASCE). 2005. Minimum Design Loads for Buildings and Other Structures.

ASCE/SEI Standard 7-05.

Bowles. 1996. Engineering Properties of Soils and their Measurement. Joseph E. Bowles.

Federal Highway Administration (FHWA). 2009. Classification of Organic Soils. FHWA/IN/JTRP-2008/2.

Terzaghi, K. 1943. Theoretical Soil Mechanics. John Wiley & Sons, New York, 510 pp.

Terzaghi. 1955. Evaluation of the Coefficients of subgrade reaction. Geotechnique, Vol. 5, No. 4.

TTL Associates, 2017. Geotechnical Drilling and Testing Investigation. Proposed Replacement Firestation. Ohio Air National Guard. May 2017.

U.S. Army Corps of Engineers (USACE). 1994. EM-1110-1-2908, Rock Foundation.

U.S. Department of Defense (DoD). 2001. Unified Facilities Criteria (UFC) 3-260-02, Pavement Design for Airfields. June.

U.S. Department of Defense (DoD). 2005. Unified Facilities Criteria (UFC) 3-570-02A, Cathodic Protection. March.

U.S. Department of Defense (DoD). 2011. Unified Facilities Criteria (UFC) 3-220-01, Geotechnical Engineering.

November.

U.S. Department of Defense (DoD). 2013. Unified Facilities Criteria (UFC) 1-201-01, Non-Permanent DoD Facilities in Support of Military Operations. January.

U.S. Department of Defense (DoD). 2013. Unified Facilities Criteria (UFC) 3-301-01, Structural Engineering. June.

U.S. Department of Defense (DoD). 2016. Unified Facilities Criteria (UFC) 3-310-04, Seismic Design of Buildings.

June.

U.S. Department of Defense (DoD). 2016. Unified Facilities Criteria (UFC) 3-200-01, DoD Building Code (General Building Requirements). June.

U.S. Department of Defense (DoD). 2017. Unified Facilities Criteria (UFC) 3-201-01, Civil Engineering Change 1.

March.

U.S. Department of Defense (DoD). 2010. Unified Facilities Criteria (UFC) 3-301-01, Structural Engineering. June.

U.S. Department of Defense (DoD). 2016. Unified Facilities Criteria (UFC) 3-301-01, Structural Engineering.

September.

U.S. Department of Defense (DoD). 2016. Unified Facilities Criteria (UFC) 3-250-01, Pavement Design for Roads and Parking Areas. November.

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Appendix A - Geotechnical Drilling and Testing Investigation Report (TTL Associates, 2017)

CH2M Hill

Corvallis, Oregon

Geotechnical Drilling and

Testing Investigation

Proposed Replacement Fire Station

Ohio Air National Guard

Mansfield, Ohio

May 2017

Teamwork - Trust - Leadership Since 1927

May 22, 2017 TTL Project No. 15029.01

Mr. Paul Davis, P.E., G.E.

CH2M Hill 1100 NE Circle Boulevard, Suite 300 Corvallis, Oregon 97330

Geotechnical Drilling and Testing Investigation

Proposed Replacement Fire Station

Ohio Air National Guard

Mansfield, Ohio

Dear Mr. Davis:

Following is the report of our geotechnical subsurface investigation for the referenced project.

This investigation was performed in general accordance with TTL Proposal No. 15029.01, dated December 22, 2016, and was authorized by a CH2M Hill Award/Contract dated January 9, 2017.

PROJECT DESCRIPTION

Based on the provided information, it is our understanding that the project consists of the construction of a proposed replacement…