Attachment 12 - Geotech Report.pdf

REPORT COVER PAGE

Geotechnical Engineering Report

VA Medical Center Garage and Parking Lot

Oklahoma City, Oklahoma

March 29, 2022

Terracon Project No. 03215009

Prepared for:

American Structurepoint, Inc

Indianapolis, Indiana

Prepared by:

Terracon Consultants, Inc.

Oklahoma City, Oklahoma

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REPORT TOPICS

INTRODUCTION

SITE CONDITIONS

PROJECT DESCRIPTION

GEOTECHNICAL CHARACTERIZATION

GEOTECHNICAL OVERVIEW

EARTHWORK

SHALLOW FOUNDATIONS

DEEP FOUNDATIONS

SEISMIC CONSIDERATIONS

FLOOR SLABS

LATERAL EARTH PRESSURES

PAVEMENTS

CORROSIVITY

GENERAL COMMENTS

ATTACHMENTS

FIGURES .............................................................. ERROR! BOOKMARK NOT DEFINED.

Note: This report was originally delivered in a web-based format. Orange Bold text in the report indicates a referenced section heading. The PDF version also includes hyperlinks which direct the reader to that section and clicking on the

GeoReport logo will bring you back to this page. For more interactive features, please view your project online at client.terracon.com.

ATTACHMENTS

EXPLORATION AND TESTING PROCEDURES

SITE LOCATION AND EXPLORATION PLANS

EXPLORATION RESULTS

SUPPORTING INFORMATION

Note: Refer to each individual Attachment for a listing of contents.

http://client.terracon.com/

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INTRODUC TION

Geotechnical Engineering Report

VA Medical Center Garage and Parking Lot

NE 16th Street and N Kelley Avenue

Oklahoma City, Oklahoma

March 29, 2022

INTRODUCTION

This report presents the results of our subsurface exploration and geotechnical engineering services performed for the proposed VA Medical Center Garage and Parking Lot to be located at

NE 16th Street and N Kelley Avenue in Oklahoma City, Oklahoma. The purpose of these services is to provide information and geotechnical engineering recommendations relative to:

■ Subsurface soil and rock conditions ■ Foundation design and construction

■ Groundwater conditions ■ Floor slab design and construction

■ Site preparation and earthwork ■ Seismic site classification per IBC

■ Lateral earth pressures ■ Excavation considerations

■ Pavement design and construction

The geotechnical engineering Scope of Services for this project included the advancement of 12 test borings to depths ranging from approximately 5 to 40.5 feet below existing site grades.

Maps showing the site and boring locations are shown in the Site Location and Exploration

Plan sections, respectively. The results of the laboratory testing performed on soil samples obtained from the site during the field exploration are included on the boring logs in the

Exploration Results section.

SITE CONDITIONS

The following description of site conditions is derived from our site visit in association with the field exploration.

Item Description

Parcel Information

The project is located at NE 16th Street and N Kelley Avenue in Oklahoma

City, Oklahoma.

See Site Location

Latitude/Longitude: 35.4848, -97.4948 (approximate)

Existing

Improvements

Existing solar-panel covered parking and drive areas, open parking lot area, light poles, a guard shack and sidewalks

VA Medical Center Garage and Parking Lot ■ Oklahoma City, Oklahoma

March 29, 2022 ■ Terracon Project No. 03215009

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Item Description

Existing Topography Gently sloping downward towards the west with about 11 feet of maximum elevation difference between the borings throughout the site.

PROJECT DESCRIPTION

Our initial understanding of the project was provided in our proposal and was discussed during project planning. A period of collaboration has transpired since the project was initiated, and Our final understanding of the project conditions is as follows:

Item Description

Proposed Structure The project includes a two to three level garage with the potential for future vertical expansion up to ten levels.

Maximum Loads

■ Compression Column Load: 1,785 kips

■ Uplift Load per Column: 255 kips

Below-Grade Structures None

Finished Floor Elevation The finished floor elevation of the structure varies across the site from 1,244 to 1,251 feet.

Pavements

Reconfigured paved driveway and parking will be constructed on the parcel.

Light Duty:

■ Autos/light trucks: 500 vehicles per day

Heavy Duty: (in addition to autos/light trucks)

■ Light delivery and trash collection vehicles: 10 vehicles per week

Tractor-trailer trucks: <1 vehicle per week

GEOTECHNICAL CHARACTERIZATION

Subsurface Profile

We have developed a general characterization of the subsurface conditions based upon our review of the subsurface exploration, laboratory data, geologic setting and our understanding of the project. This characterization, termed GeoModel, forms the basis of our geotechnical calculations and evaluation of site preparation and foundation options. Conditions encountered at each exploration point are indicated on the individual logs. The individual logs can be found in the

Exploration Results section and the GeoModel can be found in the Figures section of this report.

As part of our analyses, we identified the following model layers within the subsurface profile. For a more detailed view of the model layer depths at each boring location, refer to the GeoModel.

Model Layer Layer Name General Description

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1 Sand Silty Sand (SM)

2 Lean Clay Lean Clay (CL), Shaley Lean Clay (CL)

3 Fill Lean Clay with Sand, Sandy Lean Clay

4 Bedrock 1 Highly Weathered Shale

5 Bedrock 2 Highly Weathered Sandstone

6 Bedrock 3 Weathered Shale

7 Bedrock 4 Weathered Sandstone

The conditions noted in the GeoModel were/were not consistent with those anticipated in the

Stage 1 GeoReport®. The following variations are of note:

■ Existing clay fill materials with varying amounts of sand were encountered to depths of approximately 3.5 to 5 feet in borings B-8, C-3, and C-4.

Groundwater Conditions

The boreholes were observed while drilling and after completion for the presence and level of groundwater. The water levels observed in the boreholes can be found on the boring logs in

Exploration Results, and are summarized below.

Boring Number

Approximate Depth to

Groundwater while Drilling

(feet)

Approximate Depth to

Groundwater after Drilling

(feet)

B-2 9.5 N/A

1. Below ground surface

Because drilling fluid was introduced into borings B-2, B-5, and B-7, groundwater observations were made prior to the introduction of drilling fluid. As reported in the lower left corner of the boring logs, groundwater was not encountered in borings B-5,and B-7 at depths ranging from about 10 to 15 feet prior to the introduction of drilling fluid.

Groundwater was not observed in the remaining borings while drilling, or for the short duration the borings could remain open. However, this does not necessarily mean the borings terminated above groundwater, or the water levels summarized above are stable groundwater levels. Due to the low permeability of the soils encountered in the borings, a relatively long period may be necessary for a groundwater level to develop and stabilize in a borehole. Long term observations in piezometers or observation wells sealed from the influence of surface water are often required to define groundwater levels in materials of this type.

Groundwater level fluctuations occur due to seasonal variations in the amount of rainfall, runoff and other factors not evident at the time the borings were performed. Therefore, groundwater

Responsive ■ Resourceful ■ Reliable 4 levels during construction or at other times in the life of the structure may be higher or lower than the levels indicated on the boring logs. The possibility of groundwater level fluctuations should be considered when developing the design and construction plans for the project.

GEOTECHNICAL OVERVIEW

The borings generally encountered existing lean clay fill and native clays to depths of approximately 0.5 to 7 feet underlain by highly weathered to weathered shale and/or sandstone to the boring termination depths. Clays exhibiting moderate shrink/swell potential are present within the anticipated depth of seasonal moisture change on northern 1/3 portion of the parking garage. Hence, some removal of exisyting soil and replacement with cohesive low volume change soils will be required to provide adequate support for portions of the parking garage floor slabs.

The Floor Slabs section addresses slab-on-grade support of the parking garage.

Additional site preparation recommendations, including subgrade improvement and fill placement, are provided in the Earthwork section.

The Shallow Foundations section addresses support of the canopy on tested and approved new and/or existing fill or undisturbed native soils. The Deep Foundations section addresses support of the parking garage bearing in the weathered shale and/or sandstone.

The Pavements section contains recommendations for both rigid (PCC) and flexible (AC) pavement sections for the paved sections. Subgrade stabilization of the on-site soils with Class

“C” fly ash or cement kiln dust (CKD) or placing a layer of aggregate beneath the pavements is recommended to improve long-term support for new pavements.

Expansive soils are present on this site. This report provides recommendations to help mitigate the effects of soil shrinkage and expansion. However, even if these procedures are followed, some movement and (at least minor) cracking in the structure should be anticipated. The severity of cracking and other damage such as uneven floor slabs will probably increase if modification of the site results in excessive wetting or drying of the expansive soils. Eliminating the risk of movement and distress may not be feasible, but it may be possible to further reduce the risk of movement if significantly more expensive measures are used during construction. We would be please to discuss other construction alternatives with you upon request.

Support of floor slabs and pavements on or above existing fill materials is discussed in this report.

However, even with the recommended construction procedures, there is an inherent risk for the owner that compressible fill or unsuitable material within or buried by the fill will not be discovered.

This risk of unforeseen conditions cannot be eliminated without completely removing the existing fill, but can be reduced by following the recommendations contained in this report. To take advantage of the cost benefit of not removing the entire amount of undocumented fill, the owner must be willing to accept the risk associated with building over the undocumented fills following

Responsive ■ Resourceful ■ Reliable 5 the recommended reworking of the material. Should this be the case, development can be supported on a shallow foundation system.

The General Comments section provides an understanding of the report limitations.

EARTHWORK

The following sections provide recommendations for use in the preparation of specifications for the work. Recommendations include critical quality criteria, as necessary, to render the site in the state considered in our geotechnical engineering evaluation for foundations, floor slabs, and pavements.

Site Preparation

Site preparation should include removing the existing foundations, pavement and any other unsuitable surface materials from the areas of new construction. The depressions or excavations created during demolition of the existing structures should be cleaned of loose material and backfilled as outlined in the following paragraphs. Actual removal depths should be determined at the time of construction by a representative of the geotechnical engineer.

Weather conditions will influence site preparation procedures. If soil moisture contents are high, which could be the case if construction begins following a wet period, drying of exposed soils may be required to develop a stable base on which to place fill. Scarifying and aerating the soil may be sufficient to reduce the moisture content during warm, dry weather, but this will be less effective during periods of cool or wet weather. Removing and replacing wet soils should be expected if site preparation is conducted during cool and/or wet conditions.

After site striping and performing any required cuts, but before placing any fill or constructing floor slabs, we recommend undercutting the northern 1/3 of the building area to allow construction of a minimum 2-foot thickness of a cohesive low volume change soil below the design finished subgrade elevation. The cohesive low volume change soil zone should extend beyond the building footprint at least 1 foot laterally for each foot of fill required to develop design grade.

After performing any required undercut, but before placing any fill, we recommend exposed soils be proofrolled with a loaded, tandem-axle dump truck weighing at least 25 tons (under the observation of Terracon personnel) to locate any soft or unstable zones. The proofrolling should involve overlapping passes in mutually perpendicular directions. Where rutting or pumping is observed during proofrolling, the unstable soils should be overexcavated and replaced with an approved low plasticity cohesive soil as described in the following sections if it cannot be effectively compacted in-place. Proof-rolling will not be required in areas where highly weathered to weathered shale and/or sandstone is exposed.

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After a successful proofroll, we recommend scarifying the exposed subgrade soils to a minimum depth of 8 inches in the building area, and in the pavement area if fill is required. The scarified soil should be adjusted to a workable moisture content that is at or above its optimum value, as determined by test method ASTM D698 (standard Proctor), prior to being compacted to at least

95 percent of its maximum dry density. Scarification and compaction will not be required in areas where highly weathered to weathered shale and/or sandstone is exposed.

Unstable Soil

Elevated moisture contents were encountered in boring C-4 at the time of this investigation. In addition, we expect the subgrade soils beneath the existing pavement to have accumulated moisture over the life of the pavement. Therefore, it is possible that wet or unstable areas will be encountered during proofrolling. The amount of unstable soils that may have to be overexcavated and replaced should be determined at the time of construction.

Existing Fill

As noted in Geotechnical Characterization, borings B-8, C-3 and C-4 encountered existing fill to depths ranging from about 0 to 5 feet. The fill appears to have been placed in a controlled manner, but we have no records to indicate the degree of control. Support of footings, floor slabs, and pavements, on or above existing fill soils, is discussed in this report. However, even with the recommended construction procedures, there is inherent risk for the owner that compressible fill or unsuitable material, within or buried by the fill will, not be discovered. This risk of unforeseen conditions cannot be eliminated without completely removing the existing fill, but can be reduced by following the recommendations contained in this report.

Fill Material Types

All fill required to develop the design subgrade elevation should be an approved cohesive or cohesionless material that is free of organic matter and debris. Earthen materials used for fill should meet the following material property requirements:

Soil Type USCS Classification Acceptable Location for Placement

Low Plasticity Cohesive Soils-

Liquid Limit less than 40

Plasticity index between 5 and 15

With at least 60% passing #200 sieve

CL, CL-ML All locations and elevations

On-Site Soils

CL, SM Pavement and non-structure areas

ODOT Type “A” Aggregate meeting the requirements of Section 703.01

GW, GP All locations and elevations

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Soil Type USCS Classification Acceptable Location for Placement

1. Fill should consist of approved materials free of organic matter and debris. Frozen material should not be used, and fill should not be placed on a frozen subgrade. A sample of each material type should be submitted to the Geotechnical Engineer for evaluation prior to use on this site.

2. Some of the on-site soils appear suitable for use as low plasticity cohesive soil. However, this should be verified during construction by further testing.

3. Provided the top 8 inches of the pavement subgrade is stabilized with Class “C” fly ash or cement kiln dust

(CKD) or at least 6 inches of ODOT Type A Aggregate is placed, as noted in Pavements.

4. Recycled aggregate is not recommended.

Fill Compaction Requirements

Structural and general fill should meet the following compaction requirements.

Item Description

Maximum Lift Thickness

■ 8 inches or less in loose thickness when heavy, self-propelled compaction equipment is used

■ 4 to 6 inches in loose thickness when hand-guided equipment (i.e.

jumping jack or plate compactor) is used

Minimum Compaction

Requirements

■ Low plasticity cohesive soils: At least 95%

■ Type “A” aggregate base: At least 98%

■ Stabilized depth of pavement subgrade: At least 98%

Water Content Range

■ Low Plasticity Cohesive Soil: Workable moisture content that is at or above its optimum value

■ Cohesionless Soil: Workable moisture content that is within 2 percent of its optimum value

■ ODOT Type A Aggregate: Workable moisture content

1. Maximum density and optimum water content as determined by the standard Proctor test (ASTM D 698).

Utility Trench Backfill

For low permeability subgrades, utility trenches are a common source of water infiltration and migration. All trenches created for utility access under the building should be effectively sealed to restrict water intrusion and flow along the trenches. We recommend using a clay soil to construct an effective clay trench plug that extends at least 5 feet out from the face of the building. The clay should have a minimum plasticity index (PI) of 15 and be placed in controlled lifts not exceeding 9 inches in loose thickness so as to surround the utility line and fill the trench. Each lift of clay backfill should be compacted to at least 95 percent of the material’s maximum standard

Proctor dry density, ASTM 698, at a minimum moisture content that is above its optimum value.

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Grading and Drainage

Effective drainage should be developed during construction and maintained throughout the life of the development. Infiltration of water into utility trenches or foundation excavations should be prevented during construction. Planters and other surface features that could retain water in areas adjacent to the building or pavements should be sealed or eliminated. In areas where sidewalks or paving do not immediately adjoin the structure, we recommend that protective slopes be provided with a minimum grade of approximately 5 percent for at least 10 feet from perimeter walls. Backfill against footings, exterior walls, and in utility and sprinkler line trenches should be well compacted and free of all construction debris to reduce moisture infiltration.

Downspouts, roof drains or scuppers should discharge in a manner that carries the water several feet away from the building when the ground surface adjacent to the structure is not protected by exterior slabs or paving. Sprinkler systems should not be installed within 5 feet of foundation walls. Landscape irrigation adjacent to the foundation systems should be minimized or eliminated.

Earthwork Construction Considerations

Upon completion of filling and grading, care should be taken to maintain the subgrade water content prior to construction of floor slabs. Construction traffic over the completed subgrades should be avoided. The site should also be graded to prevent ponding of surface water on the prepared subgrades or in excavations. Water collecting over or adjacent to construction areas should be removed. If the subgrade freezes, desiccates, saturates, or is disturbed, the affected material should be removed, or the materials should be scarified, moisture conditioned, and recompacted prior to floor slab construction.

As a minimum, excavations should be performed in accordance with OSHA 29 CFR, Part 1926, Subpart P, “Excavations” and its appendices, and in accordance with any applicable local, and/or state regulations.

Construction site safety is the sole responsibility of the contractor who controls the means, methods, and sequencing of construction operations. Under no circumstances shall the information provided herein be interpreted to mean Terracon is assuming responsibility for construction site safety, or the contractor's activities; such responsibility shall neither be implied nor inferred.

Excavations

We anticipate that excavations for the structure will extend into weathered bedrock. Rock formations that have standard penetration test results of 4 or more inches per 50 blows can usually be excavated with heavy excavation equipment equipped with ripping teeth. Rock formations that have standard penetration test results of 3 inches or less per 50 blows usually

Responsive ■ Resourceful ■ Reliable 9 require either pneumatic breaking equipment or blasting to remove. Variations in hardness of rock will likely can occur with depth and distance from the borings.

Construction Observation and Testing

The earthwork efforts should be monitored under the direction of the Geotechnical Engineer.

Monitoring should include documentation of adequate removal of vegetation and topsoil, proofrolling, and mitigation of areas delineated by the proofroll to require mitigation.

Each lift of compacted fill should be tested, evaluated, and reworked, as necessary, until approved by the Geotechnical Engineer prior to placement of additional lifts. Each lift of fill should be tested for density and water content at a frequency of at least one test for every 2,500 square feet of compacted fill in the building areas and 5,000 square feet in pavement areas. One density and water content test should be performed for every 50 linear feet of compacted utility trench backfill.

In areas of foundation excavations, the bearing subgrade should be evaluated under the direction of the Geotechnical Engineer. If unanticipated conditions are encountered, the Geotechnical

Engineer should prescribe mitigation options.

In addition to the documentation of the essential parameters necessary for construction, the continuation of the Geotechnical Engineer into the construction phase of the project provides the continuity to maintain the Geotechnical Engineer’s evaluation of subsurface conditions, including assessing variations and associated design changes.

SHALLOW FOUNDATIONS

Shallow footings can be used to support of lightly-loaded auxiliary structures bearing on engineered fill and/or native soils. If the site has been prepared in accordance with the requirements noted in

Earthwork, the following design parameters are applicable for shallow footing foundations.

Design Parameters – Canopy

Item Description

Maximum Net Allowable Bearing Pressure 1, 2, 3

■ 2,000 psf (foundations bearing within tested and approved new and/or existing fill)

■ 5,000 psf (foundation bearing on native undisturbed soils)

■ 10,000 psf (foundation bearing on highly weathered to weathered bedrock)

Required Bearing Stratum

Tested and approved new and/or existing fill or undisturbed native soils

Minimum Foundation Width Columns: 30 inches

Continuous: 18 inches

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Item Description

Allowable Passive Resistance

(equivalent fluid pressures)

150 pcf

Allowable Coefficient of Sliding Friction

■ Tested and approved new and/or existing fill or native undisturbed soils: 0.2

■ Highly weathered to weathered bedrock: 0.4

Minimum Embedment below

Finished Grade

Exterior footings in unheated areas: 30 inches

Interior footings in heated areas: 12 inches

Estimated Total Settlement from Structural

Loads

Less than 1 inch

Estimated Differential Settlement About 1/2 of total settlement

1. The maximum net allowable bearing pressure is the pressure in excess of the minimum surrounding overburden pressure at the footing base elevation. An appropriate factor of safety has been applied. The allowable bearing pressure has a safety factor of 3 or greater. The bearing pressure can be increased by 1/3 for transient loads unless those loads have been factored to account for transient conditions.

2. Values provided are for maximum loads noted in Project Description.

3. Due to the presence of the fill in isolated areas of the site, Terracon personnel should be retained to observe and evaluate that footing excavations terminate in soils suitable for the actual design bearing pressure. This should include performing shallow depth hand augers, T-probes, calibrated penetrometer tests and dynamic cone penetrometer (DCP) tests in the footing excavations. When DCP tests are used to evaluate the suitability of the bearing soils, they should be performed at the base of the footing excavation and at every 12 inches to a depth equal to the width of column footings or two times the width of continuous wall footings. However, in no case should the suitability of the bearing soils be evaluated to a depth that is less than 3 feet below the base of footings. If unsuitable soil is present, the excavation should be extended until suitable material is encountered. Unsuitable soil removal should also extend at least 8 inches beyond the foundation edge for each 12-inch thickness of unsuitable soil being removed. The material removed should be replaced with lean concrete or an approved structural fill that is compacted as described in the Earthwork section of this report.

4. Unsuitable or soft soils should be over-excavated and replaced per the recommendations presented in the Earthwork.

5. With an applied safety factor of 2. Use of passive earth pressures require the sides of the excavation for the spread footing foundation to be nearly vertical and the concrete placed neat against these vertical faces or that the footing forms be removed and compacted structural fill be placed against the vertical footing face. Unless pavements or on-grade slabs are provided up to and above the footings, the allowable passive pressure should be disregarded to a depth of 2.5 feet below the final grade.

6. With an applied safety factor of 2. Can be used to compute sliding resistance where foundations are placed on suitable soil/materials. Should be neglected for foundations subject to net uplift conditions.

7. Embedment necessary to minimize the effects of frost and/or seasonal water content variations. For sloping ground, maintain depth below the lowest adjacent exterior grade within 5 horizontal feet of the structure.

8. It appears that the shallow footings may bear in a combination of native undisturbed soils, new fill and/or weathered bedrock. To reduce the concentration of stress due to non-uniform support beneath the structure and to reduce differential settlement, we recommend undercutting the areas where weathered bedrock is encountered 2 feet beneath the footings to allow placement of moisture conditioned and compacted low volume change soil. The excavation beneath the footings should extend laterally at least 1 foot beyond the sides of the footings.

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Foundation Construction Considerations

As noted in Earthwork, the footing excavations should be evaluated under the direction of the

Geotechnical Engineer. The base of all foundation excavations should be free of water and loose soil, prior to placing concrete. Concrete should be placed soon after excavating to reduce bearing soil disturbance. Care should be taken to prevent wetting or drying of the bearing materials during construction. Excessively wet or dry material or any loose/disturbed material in the bottom of the footing excavations should be removed/reconditioned before foundation concrete is placed.

If unsuitable bearing soils are encountered at the base of the planned footing excavation, the excavation should be extended deeper to suitable soils, and the footings could bear directly on these soils at the lower level or on lean concrete backfill placed in the excavations. This is illustrated on the sketch below.

Over-excavation for structural fill placement below footings should be conducted as shown below.

The over-excavation should be backfilled up to the footing base elevation, with low plasticity cohesive or cohesionless material placed, as recommended in the Earthwork section.

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DEEP FOUNDATIONS

Drilled Pier Design Parameters – Parking Garage

Soil design parameters are provided in the table below for the design of drilled pier foundations.

Description Value

Foundation Type Straight shaft drilled piers

Bearing Material

Approved weathered shale or weathered sandstone encountered at depths of approximately

13.5 to 18.5 feet (approximate elevations of 89 to

95 feet) below the existing grade

Minimum Embedment 5 feet into approved weathered shale or weathered sandstone

Maximum Net Allowable Bearing Pressure 2,3 and Minimum Embedment into Bearing

Material

50,000 psf for piers penetrating a minimum of 5 feet or two pier diameters, whichever greater into approved weathered shale or sandstone

Maximum Allowable Skin Friction 2,4

1,000 psf within highly weathered shale and/or sandstone

2,500 psf within weathered shale and/or sandstone

Allowable Passive Pressure

1,500 psf within overburden soils

8,000 psf within highly weathered shale and/or sandstone

30,000 psf within weathered shale and/or sandstone

Minimum Pier Diameter 24 inches

Minimum Grade Beam Embedment Depth

Below Finished Grade

30 inches

Minimum Void Space Beneath Grade Beam 4 inches

Estimated Total Settlement from Structural

Loads ½ inch

Estimated Differential Settlement Less than ½ inch

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Description Value

1. See Subsurface Profile in Geotechnical Characterization for more details on stratigraphy.

2. Design capacities are dependent upon the method of installation, and quality control parameters. The values provided are estimates and should be verified when installation protocol have been finalized.

3. The maximum net allowable bearing pressures are the pressure in excess of the minimum surrounding overburden pressure at the foundation base elevation. The allowable bearing pressures have a safety factor of approximately 3. The bearing pressures can be increased by 1/3 for transient loads unless those loads have been factored to account for transient conditions. Use a soil unit weight of 120 pcf to estimate the overburden pressure.

4. Skin friction may be used to resist both upward and downward axial forces. The allowable skin friction values have a safety factor of approximately 2.

5. With an applied safety factor of 2. These values assume that the foundations are poured directly against undisturbed materials. Unless pavements or on-grade slabs are provided up to and above the foundations, the allowable passive pressure should be disregarded to a depth of 3 feet below the final grade.

6. Assume that enough steel reinforcement is provided to provide adequate structural integrity.

7. Grade beams should be structurally connected to the top of the piers.

8. Excavation for grade beams should be free of loose material and protection should be provided to prevent future filling of the void by sloughing soils.

Drilled Pier Lateral Load Analyses

Using the LPILE computer program, we determined the maximum lateral load at the pier head at a deflection of 0.25 inch.

Lateral load analyses were performed for:

■ five pier diameters, i.e., 24, 36, 48, 60, and 72 inches

■ two boundary conditions, i.e., free- and fixed-head conditions

■ two reinforcing ratios, i.e., 0.5% and 2% steel

Lateral load analyses were based on:

■ one subsurface profile consisting of clay (modeled using the stiff clay without free water model with undrained cohesion of 2,000 psf and strain factor of 0) extending to EL. 1230 feet underlain by shale bedrock (modeled using the weak rock model with uniaxial compressive strength of 125 psi, initial modulus of rock mass of 7,000 psi, RQD of 0, and strain factor of 0.0005)

■ the top of pier at a depth of 3 feet below the finished floor elevation

■ the bottom of pier and axial compression/uplift load (acting on the top of pier) obtained from the drawings tittled “Caisson Gravity Loading Diagram” prepared by American

Structurepoint, Inc.

■ concrete strength of 4,000 psi

■ #4 ties for shear reinforcement

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■ Grade 60 longitudinal reinforcement

■ no group effects due to lateral loads

Results of lateral load analyses are provided in the Figures section of this report.

Drilled Pier Construction Considerations

Our drilling rig used an earth auger to penetrate the overburden soils, highly weathered shale, highly weathered sandstone, weathered shale, and weathered sandstone. However, a rock bit may be required to extend the drilled pier excavations into the highly weathered shale, highly weathered sandstone, weathered shale, and weathered sandstone. We do not expect temporary casing will be needed to prevent caving of the excavation sides; however, the final determination should be made at the time of construction.

Groundwater was encountered during the field exploration; therefore, we anticipate dewatering will be required during pier construction. However, the need for dewatering will also depend on the actual groundwater conditions at the time of construction. The bottom of the pier excavation should be cleaned of debris, loose or disturbed soil, and water, if any, prior to placing reinforcing steel and concrete. If water is encountered and cannot be removed, the concrete should be placed using a tremie pipe and placed from the bottom of the pier excavation to the top, displacing the water to the surface. Concrete should be placed as soon as possible after the foundation excavation is completed to reduce the potential for disturbance of the bearing surface. To facilitate pier construction, concrete should be on-site and ready for placement as pier excavations are completed. In no event should the pier excavation be allowed to remain open overnight.

The drilled shaft installation process should be performed under the direction of the Geotechnical

Engineer. The Geotechnical Engineer should document the shaft installation process including soil/rock and groundwater conditions encountered, consistency with expected conditions, and details of the installed shaft.

SEISMIC CONSIDERATIONS

The seismic design requirements for buildings and other structures are based on Seismic Design

Category. Site Classification is required to determine the Seismic Design Category for a structure.

The Site Classification is based on the upper 100 feet of the site profile defined by a weighted average value of either shear wave velocity, standard penetration resistance, or undrained shear strength in accordance with Section 20.4 of ASCE 7 and the International Building Code (IBC).

Based on the soil/bedrock properties encountered at the site and as described on the exploration logs and results, it is our professional opinion that the Seismic Site Classification is C.

Subsurface explorations at this site were extended to a maximum depth of 40.5 feet. The site

Responsive ■ Resourceful ■ Reliable 15 properties below the boring depth to 100 feet were estimated based on our experience and knowledge of geologic conditions of the general area. Additional deeper borings or geophysical testing may be performed to confirm the conditions below the current boring depth.

FLOOR SLABS

The subgrade soils are comprised of moderate plasticity clays exhibiting the potential to swell with increased water content. Construction of the floor slab and revising site drainage creates the potential for gradual increased water contents within the clays. Increases in water content will cause the clays to swell and damage the floor slab. To reduce the swell potential to about 1 inch, we recommend undercutting the northern 1/3 of the building area to allow construction of a minimum 2-foot thickness of a cohesive low volume change soil below the design finished subgrade elevation.

Design parameters for floor slabs assume the requirements for Earthwork have been followed.

Specific attention should be given to positive drainage away from the building.

Floor Slab Design Parameters

Item Description

Floor Slab Support

At least 2 feet of cohesive low volume change soils prepared in accordance with Earthwork should be present below the northern 1/3 portions of the proposed building.

Estimated Modulus of

Subgrade Reaction

100 psi/in on soil subgrade

110 psi/in on a 4-inch thickness of Type “A” aggregate over soil subgrade

1. Floor slabs should be structurally independent of building footings or walls to reduce the possibility of floor slab cracking caused by differential movements between the slab and foundation.

2. Modulus of subgrade reaction is an estimated value based upon our experience with the subgrade condition, the requirements noted in Earthwork, and the floor slab support as noted in this table. It is provided for point loads. For large area loads the modulus of subgrade reaction would be lower.

3. Floor slabs constructed on a 4-inch thickness of Type “A” aggregate can be designed using a subgrade modulus of 110 pci.

The use of a vapor retarder should be considered beneath concrete slabs on grade covered with wood, tile, carpet, or other moisture sensitive or impervious coverings, or when the slab will support equipment sensitive to moisture. When conditions warrant the use of a vapor retarder, the slab designer should refer to ACI 302 and/or ACI 360 for procedures and cautions regarding the use and placement of a vapor retarder.

Saw-cut control joints should be placed in the slab to help control the location and extent of cracking. For additional recommendations refer to the ACI Design Manual. Joints or cracks should

Responsive ■ Resourceful ■ Reliable 16 be sealed with a water-proof, non-extruding compressible compound specifically recommended for heavy duty concrete pavement and wet environments.

Where floor slabs are tied to perimeter walls or turn-down slabs to meet structural or other construction objectives, our experience indicates differential movement between the walls and slabs will likely be observed in adjacent slab expansion joints or floor slab cracks beyond the length of the structural dowels. The Structural Engineer should account for potential differential settlement through use of sufficient control joints, appropriate reinforcing or other means.

Settlement of floor slabs supported on existing fill materials cannot be accurately predicted, but could be larger than normal and result in some cracking. Mitigation measures, as noted in

Existing Fill within Earthwork, are critical to the performance of floor slabs. In addition to the mitigation measures, the floor slab can be stiffened by adding steel reinforcement, grade beams and/or post-tensioned elements.

Floor Slab Construction Considerations

Finished subgrade, within and for at least 10 feet beyond the floor slab, should be protected from traffic, rutting, or other disturbance and maintained in a relatively moist condition until floor slabs are constructed. If the subgrade should become damaged or desiccated prior to construction of floor slabs, the affected material should be removed and structural fill should be added to replace the resulting excavation. Final conditioning of the finished subgrade should be performed immediately prior to placement of the floor slab support course.

The Geotechnical Engineer should approve the condition of the floor slab subgrades immediately prior to placement of the floor slab support course, reinforcing steel, and concrete. Attention should be paid to high traffic areas that were rutted and disturbed earlier, and to areas where backfilled trenches are located.

LATERAL EARTH PRESSURES

Design Parameters

Reinforced concrete walls with unbalanced backfill levels on opposite sides should be designed for earth pressures at least equal to those indicated in the following table. Earth pressures will be influenced by structural design of the walls, conditions of wall restraint, methods of construction and/or compaction and the strength of the materials being restrained. Two wall restraint conditions are shown. Active earth pressure is commonly used for design of free-standing cantilever retaining walls and assumes wall movement. The "at-rest" condition assumes no wall movement.

The recommended design lateral earth pressures do not include a factor of safety and do not provide for possible hydrostatic pressure on the walls.

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Lateral Earth Pressure Design Parameters

Earth Pressure

Condition

Coefficient for

Backfill Type

Surcharge

Pressure p1

(psf)

Earth Pressure p2

(psf)

Equivalent Fluid

Pressure (pcf)

Active (Ka) Granular - 0.33

Lean Clay - 0.42

(0.33)S

(0.42)S

(40)H

(50)H

At-Rest (Ko) Granular - 0.46

Lean Clay - 0.58

(0.46)S

(0.58)S

(55)H

(70)H

Passive (Kp) Granular - 3.0

Lean Clay - 2.4

Conditions applicable to the above table include:

■ For active earth pressure, wall must rotate about base, with top lateral movements 0.002

H to 0.004 Z, where H is wall height.

■ For passive earth pressure, wall must move horizontally to mobilize resistance.

■ Uniform surcharge, where S is surcharge pressure.

■ In-situ soil backfill weight a maximum of 120 pcf.

■ Horizontal backfill, compacted to at least 95 percent of standard Proctor (ASTM D-698) maximum dry density.

■ Loading from heavy compaction equipment not included.

■ No groundwater acting on wall.

■ No safety factor included.

■ Ignore passive pressure in frost zone (18 inches).

Backfill placed against structures should consist of granular soils or low plasticity cohesive soils

(PI ≤ 15). For the granular values to be valid, the granular backfill must extend out and up from the base of the wall at an angle of at least 45 and 60 degrees from vertical for the at-rest and passive cases, respectively. Additionally, the granular backfill must extend out from the base of the wall at an angle of at least 30 degrees from vertical for the active case. To calculate the

Responsive ■ Resourceful ■ Reliable 18 resistance to sliding, a values of 0.2 and 0.4 should be used as the allowable coefficients of friction between the footing and the underlying soil or weathered bedrock, respectively.

Subsurface Drainage for Below-Grade Walls

We recommend installing an exterior perimeter drain system along below-grade walls. The exterior perimeter drains should be installed at the foundation level as shown on the adjacent figure and described in the following notes.

■ Granular backfill should be clean, free-draining sand or crushed stone.

■ Perforated pipe should be rigid PVC, sized to transport the expected water.

■ Perforated pipe should be surrounded by at least 4 inches of ASTM C-33 No. 57 stone or equivalent with the stone and pipe encased in an approved filter fabric to restrict the migration of fines into the drain system.

■ Exterior ground surface should consist of a 12-inch compacted clay cap or pavement section sloped to drain from building.

If adequate drainage is not possible, then combined hydrostatic and lateral earth pressures should be calculated for lean clay backfill using an equivalent fluid weighing 90 and 100 pcf for active and at-rest conditions, respectively. For granular backfill, an equivalent fluid weighing 85 and 90 pcf should be used for active and at-rest, respectively. These pressures do not include the influence of surcharge, equipment or floor loading, which should be added. Heavy equipment should not operate within a distance closer than the exposed height of retaining walls to prevent imposing lateral pressures larger than those provided.

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PAVEMENTS

General Pavement Comments

Pavement designs are provided for the traffic conditions and pavement life conditions as noted in

Project Description and in the following sections of this report. A critical aspect of pavement performance is site preparation. Pavement designs noted in this section are considered appropriate for this project provided the subgrade has been prepared as recommended in the

Earthwork section and in the following sections of this report.

Pavement Support

To reduce potential trafficability problems and strength loss, and to improve the long-term subgrade support, we recommend that the top 8 inches of the subgrade be stabilized with Class

“C” fly ash or cement kiln dust. Based on past experience with soils similar to those present at the site, we estimate 10 to 14 percent Class “C” fly ash or cement kiln dust will be needed to adequately stabilize the on-site soils. The actual percentage of additive should be determined at the time of construction by the Geotechnical Engineer. Before compaction, the stabilized soil zone should be adjusted to within 2 percent of the material’s optimum moisture as determined by test method ASTM D698. After conditioning the soil to the required moisture content, the stabilized subgrade should be compacted to at least 98 percent of the material’s maximum dry density as determined by test method ASTM D698. Compaction should be completed within about two hours after initially mixing the soil and stabilizing agent to optimize the stabilization benefit.

As an alternative to subgrade stabilization, we recommend placing at least 6 inches of ODOT

Type “A” aggregate base meeting the requirements of Section 703.01. The aggregate should be spread and densified to at least 98 percent of the material’s maximum dry density as determined by the standard Proctor test method ASTM D698.

Pavement Section Thicknesses

The following table provides options for Asphaltic Concrete and Portland Cement Concrete sections:

Minimum Pavement Recommendations

Layer Thickness (inches)

Light Duty Heavy Duty

Portland Cement Concrete

(3,500 psi, Air Entrained)

5.0” Concrete

8.0” Stabilized Subgrade

OR

6.0” Concrete

8.0” Stabilized Subgrade

OR

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Minimum Pavement Recommendations

Layer Thickness (inches)

Light Duty Heavy Duty

5.0” Concrete

6.0” Type “A” Aggregate Base

6.0” Concrete

Asphaltic Concrete

2.0” Type “B” Asphaltic Concrete

3.0” Type “A” Asphaltic Concrete

8.0” Stabilized Subgrade

OR

2.0” Type “B” Asphaltic Concrete

3.0” Type “A” Asphaltic Concrete

2.0” Type “B” Asphaltic Concrete

5.0” Type “A” Asphaltic Concrete

8.0” Stabilized Subgrade

OR

2.0” Type “B” Asphaltic Concrete

5.0” Type “A” Asphaltic Concrete

1. All materials should meet the current Oklahoma Department of Transportation (ODOT) Standard Specifications for Highway and Bridge Construction. For asphaltic concrete, refer to ODOT 1988 Specifications.

2. See Project Description for more specifics regarding Light Duty and Heavy Duty traffic.

3. ODOT Type “A” aggregate base should meet the requirements of Section 703.01. The aggregate should be spread and densified to at least 98 percent of the material’s maximum dry density as determined by the standard Proctor test method ASTM D698.

Note: We recommend that reinforced concrete pads be provided in front of and beneath trash receptacles. The dumpster trucks should be parked on the rigid concrete pavement when the trash receptacles are lifted. The concrete pads should be a minimum of 7 inches thick and properly reinforced

Pavement Drainage

The pavement surfacing and adjacent sidewalks should be sloped to provide rapid drainage of surface water. Water should not be allowed to pond on or adjacent to these grade-supported slabs, since this could saturate the subgrade and contribute to premature pavement or slab deterioration.

Pavement Maintenance

The pavement sections represent minimum recommended thicknesses and, as such, periodic maintenance should be anticipated. Therefore, preventive maintenance should be planned and provided for through an on-going pavement management program. Maintenance activities are intended to slow the rate of pavement deterioration and to preserve the pavement investment.

Maintenance consists of both localized maintenance (e.g., crack and joint sealing and patching) and global maintenance (e.g., surface sealing). Preventive maintenance is usually the priority when implementing a pavement maintenance program. Additional engineering observation is recommended to determine the type and extent of a cost-effective program. Even with periodic maintenance, some movements and related cracking may still occur and repairs may be required.

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Pavement performance is affected by its surroundings. In addition to providing preventive maintenance, the civil engineer should consider the following recommendations in the design and layout of pavements:

■ Final grade adjacent to paved areas should slope down from the edges at a minimum 2%.

■ Subgrade and pavement surfaces should have a minimum 2% slope to promote proper surface drainage.

■ Install below pavement drainage systems surrounding areas anticipated for frequent wetting.

■ Install joint sealant and seal cracks immediately.

■ Seal all landscaped areas in or adjacent to pavements to reduce moisture migration to subgrade soils.

■ Place compacted, low permeability backfill against the exterior side of curb and gutter.

■ Place curb, gutter and/or sidewalk directly on clay subgrade soils rather than on unbound granular base course materials.

CORROSIVITY

The table below lists the results of laboratory soluble sulfate testing. The values may be used to estimate potential corrosive characteristics of the on-site soils with respect to contact with the various underground materials which will be used for project construction. This limited testing program should not be interpreted as a comprehensive assessment of the site, but only provides an indication of conditions at the sampled locations.

Corrosivity Test Results Summary

Boring Sample Depth

(feet) Soil Description Soluble Sulfate (mg/Kg)

B-1 3.5 – 5.0 Highly weathered shale 43.7

C-2 3.5 – 5.0 Lean clay 220.0

C-4 18.5 – 20.0 Highly weathered shale 8.37

GENERAL COMMENTS

Our analysis and opinions are based upon our understanding of the project, the geotechnical…