Terracon Project No. 03235201 Rev 1 VAMC Parking Garage Stair Tower GEO ENG RPT 12-19-2024 - signed.pdf

Report Cover Page

VAMC Parking Garage

Stair Tower Geotechnical Engineering Report

December 19, 2024 | Terracon Project No.

03235201(Revision1)

Oklahoma City, Oklahoma

Prepared for:

Specialized Engineering Solutions

10360 Ellison Cir

Omaha, Nebraska 68134

4701 North Stiles Avenue

Oklahoma City, Oklahoma 73105

P (405) 525-0453

Terracon.com

Facilities | Environmental | Geotechnical | Materials

Report Cover Letter to Sign

December 19, 2024

Specialized Engineering Solutions

10360 Ellison Cir

Omaha, Nebraska 68134

Attn: Brad Carne

P: (402) 850-4689

E: bcarne@specializedeng.com

Re: Geotechnical Engineering Report

VAMC Parking Garage Stair Tower

N Kelley Avenue and NW 13th Street

Oklahoma City, Oklahoma

Terracon Project No. 03235201(Revision1)

Dear Mr. Carne:

We have completed the scope of Geotechnical Engineering services for the above referenced project in general accordance with Terracon Proposal No. P03235201

Revision No. 2 dated October 7th, 2024. This report presents the findings of the subsurface exploration and provides geotechnical recommendations concerning earthwork and the design and construction of foundations for the proposed project.

We appreciate the opportunity to be of service to you on this project. If you have any questions concerning this report or if we may be of further service, please contact us.

Sincerely, Terracon

Cert. Of Auth. #CA-4531 exp. 6/30/25

Cody Rickman, E.I. Norman Tan, P.E.

Staff Engineer Oklahoma No. 23083

12/20/2024

Geotechnical Engineering Report

VAMC Parking Garage Stair Tower | Oklahoma City, Oklahoma

December 19, 2024 | Terracon Project No. 03235201(Revision1)

Facilities | Environmental | Geotechnical | Materials i

Table of Contents

Introduction Project Description Site Conditions Geotechnical Characterization Seismic Site Class Corrosivity Geotechnical Overview Earthwork

Demolition Subgrade Preparation Excavation Fill Material Types Fill Placement and Compaction Requirements Utility Trench Backfill Grading and Drainage Earthwork Construction Considerations Construction Observation and Testing

Mat Foundations Design Parameters Foundation Construction Considerations

Helical Piles Floor Slabs

Floor Slab Design Parameters Floor Slab Construction Considerations

Lateral Earth Pressures Design Parameters Subsurface Drainage for Below-Grade Walls

General Comments

Figures GeoModel

Attachments

Exploration and Testing Procedures Site Location and Exploration Plans

Exploration and Laboratory Results

Supporting Information

Facilities | Environmental | Geotechnical | Materials ii

Note: This report was originally delivered in a web-based format. Blue 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 logo will bring you back to this page. For more interactive features, please view your project online at client.terracon.com.

Refer to each individual Attachment for a listing of contents.

Facilities | Environmental | Geotechnical | Materials 1

Introduction

This report presents the results of our subsurface exploration and Geotechnical

Engineering services performed for the proposed stairwell renovation to be located at N

Kelley Avenue and NW 13th Street in Oklahoma City, Oklahoma. The purpose of these services was to provide information and geotechnical engineering recommendations relative to:

■ Subsurface soil (and rock) conditions

■ Groundwater conditions

■ Seismic site classification per IBC

■ Site preparation and earthwork

■ Demolition considerations

■ Excavation considerations

■ Foundation design and construction

■ Floor slab design and construction

■ Lateral earth pressure

The geotechnical engineering Scope of Services for this project included the advancement of 2 test borings, laboratory testing, engineering analysis, and preparation of this report. Due to overhead access issues, the borings could not be performed directly within the anticipated stairwell footprint, so the borings were completed adjacent to the existing stairwell in an effort to accurately interpolate the soil conditions.

Drawings showing the site and boring locations are shown on the Site Location and

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

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

Project

Description and

Proposed

Structure

Structures associated with the project include a stair tower for the existing parking garage.

Facilities | Environmental | Geotechnical | Materials 2

Item Description

Maximum Loads

Anticipated structural loads for the columns were provided by

Calibre Engineering. In the absence of information provided by the design team, we will use the following loads in estimating settlement based on our experience with similar projects.

• Columns: 40 kips (provided by Calibre)

• Walls: 2 to 3 kips per linear foot (klf)

• Slabs: 125 pounds per square foot (psf)

Grading/Slopes Approximately 2 feet of cut and 2 feet of fill will be required to develop final grade, excluding remedial grading requirements.

Terracon should be notified if any of the above information is inconsistent with the planned construction, especially the grading limits, as modifications to our recommendations may be necessary.

Site Conditions

The following description of site conditions is derived from our site visit in association with the field exploration and our review of publicly available geologic and topographic maps.

Item Description

Parcel

Information

The project is located at N Kelley Avenue and NW 13th Street in

Oklahoma City, Oklahoma.

Latitude/Longitude (approximate) 35.4827° N 97.4949° W See

Site Location

Existing

Improvements

Based on current imagery from Google Earth Pro, the site contains an existing parking garage, parking and drive areas, grass, trees, and sidewalks

Current Ground

Cover Concrete and asphalt pavement

Existing

Topography

Gently sloping downward from the northeast to the southwest with about 10.5 feet of maximum elevation difference between the borings.

Geotechnical Characterization

We have developed a general characterization of the subsurface conditions based upon our review of the subsurface exploration, laboratory data, geologic setting and our

Facilities | Environmental | Geotechnical | Materials 3 understanding of the project. This characterization, termed GeoModel, forms the basis of our geotechnical calculations and evaluation of the site. Conditions observed at each exploration point are indicated on the individual logs. The individual logs can be found in the Exploration Results and the GeoModel can be found in the Figures attachment 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

1 Clay Lean Clay (CL) and Shaley Lean Clay (CL) with varying amounts of sand

2 Gravel Poorly Graded Gravel with Silt (GP-GM)

3 Bedrock Weathered Shale

The boreholes were observed while drilling and after completion for the presence and level of groundwater.

Groundwater was not observed in the borings while drilling, or for the short duration the borings could remain open. However, this does not necessarily mean the borings terminated above groundwater. 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 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.

Seismic Site Class

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

Facilities | Environmental | Geotechnical | Materials 4

ASCE 7 and the International Building Code (IBC). Based on the soil/bedrock properties observed at the site and as described on the exploration logs and results, our professional opinion is for that a Seismic Site Classification of C be considered for the project. Subsurface explorations at this site were extended to a maximum depth of 29 feet. The site properties below the maximum boring depth were estimated based on our experience and knowledge of geologic conditions of the general area. Upon request, we could perform deeper borings or geophysical testing to confirm the conditions below the current maximum boring depth.

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.

Corrosivity Test Results Summary

Boring

Sample

Depth

(feet)

Soil

Description

Soluble Sulfate

(mg / Kg)

Reporting

Limit Dilution

B-1 1.0 – 2.5 CL 129 3.00 1

B-2 3.5 – 5.0 CL 23 3.00 1

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.

Consultation with a NACE certified corrosion professional is recommended for buried metals on the site.

Geotechnical Overview

The site appears suitable for the proposed construction based upon geotechnical conditions encountered in the test borings, provided that the recommendations provided in this report are implemented in the design and construction phases of this project.

The near surface, stiff to very stiff medium plasticity lean clay could become unstable with typical earthwork and construction traffic, especially after precipitation events. The effective drainage should be completed early in the construction sequence and maintained after construction to avoid potential issues. If possible, the grading should be performed during the warmer and drier times of the year. If grading is performed

Facilities | Environmental | Geotechnical | Materials 5 during the winter months, an increased risk for possible undercutting and replacement of unstable subgrade will persist. Additional site preparation recommendations, including subgrade improvement and fill placement, are provided in the Earthwork section.

The Mat Foundations section addresses support of the stairwell bearing in the native very stiff lean clay or shaley lean clay. Helical Piles may also be considered as a foundation option for the stairwell. The Floor Slabs section addresses slab-on-grade support of the structure using overexcavation techniques.

The recommendations contained in this report are based upon the results of field and laboratory testing (presented in the Exploration Results), engineering analyses, and our current understanding of the proposed project. The General Comments section provides an understanding of the report limitations.

Earthwork

Earthwork is anticipated to include demolition, clearing and excavations. 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 and floor slabs.

Demolition

We recommend existing foundations, slabs, and utilities be removed from within the proposed stairwell footprint. The depressions or excavations created during demolition of the existing structure 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.

Subgrade Preparation

After removing the vegetation, topsoil, slabs and performing any required cuts, but before placing any fill or constructing the floor slab, we recommend undercutting the stairwell area to allow construction of a minimum 1.5-feet thickness of low volume change fill below the design finish subgrade elevation. The zone of fill compacted to meet this criteria should extend beyond the structure footprint at least 1 foot laterally for each foot of fill required to develop design grade.

Due to site constraints, we anticipate that proof rolling may be difficult to perform. We recommend a qualified soil technician probe the area with a T-probe or Kessler DCP to determine the depth and extents of any soft subgrade that may be encountered. The

Facilities | Environmental | Geotechnical | Materials 6 soft or unstable soils should be overexcavated and replaced with an approved low volume change soil, moisture conditioned and recompacted. We recommend maintaining good drainage during construction to promote ideal equipment mobility and optimum earthwork compaction.

All exposed areas which will receive fill, once properly cleared and benched where necessary, should be scarified to a minimum depth of 8 inches, moisture conditioned as necessary, and compacted per the compaction requirements in this report. Compacted structural fill soils should then be placed to the proposed design grade and the moisture content and compaction of subgrade soils should be maintained until foundation construction.

Based upon the subsurface conditions determined from the geotechnical exploration, subgrade soils exposed during construction are anticipated to be relatively workable;

however, the workability of the subgrade may be affected by precipitation, repetitive construction traffic or other factors. If unworkable conditions develop, workability may be improved by scarifying and drying.

Excavation

We anticipate that excavations for the proposed construction can be accomplished with conventional earthmoving equipment. The bottom of excavations should be thoroughly cleaned of loose soils and disturbed materials prior to backfill placement and/or construction.

We anticipate that excavations for the stairwell foundation may 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 require either pneumatic breaking equipment or blasting to remove. Variations in hardness of rock will likely occur with depth and distance from the borings.

Fill Material Types

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

Facilities | Environmental | Geotechnical | Materials 7

Fill Type1

USCS

Classification Acceptable Location for Placement

Low Volume Change

(LVC) material

CL

(LL<40 and

PI<15)

At least 60% passing No. 200 sieve

All locations and elevations, except where free-draining material is required

ODOT Type “A”

Aggregate meeting the requirements of

Section 703.01

GW, GP All locations and elevations

1. Engineered fill should consist of approved materials that are free of organic matter and debris. Frozen material should not be used, and fill should not be placed on a frozen subgrade.

2. Recycled aggregate is not recommended.

Fill Placement and 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

Cohesive Soils: At least 95%

ODOT Type A Aggregate: At least 98%

Water Content

Range

Cohesive Soils: Workable moisture content that is optimum or above

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

Any soft or unsuitable materials encountered at the bottom of utility trench excavations should be removed and replaced with engineered fill or bedding material in accordance

Facilities | Environmental | Geotechnical | Materials 8 with public works specifications for the utility be supported. This recommendation is particularly applicable to utility work requiring grade control and/or in areas where subsequent grade raising could cause settlement in the subgrade supporting the utility.

Trench excavation should not be conducted below a downward 1:1 projection from existing foundations without engineering review of shoring requirements and geotechnical observation during construction.

Trench backfill should be mechanically placed and compacted as discussed earlier in this report. Compaction of initial lifts should be accomplished with hand-operated tampers or other lightweight compactors. Where trenches are placed beneath slabs or footings, the backfill should satisfy the gradation and expansion index requirements of engineered fill discussed in this report. Flooding or jetting for placement and compaction of backfill is not recommended.

Utility trenches penetrating beneath the structure should be effectively sealed to restrict water intrusion and flow through the trenches, which could migrate below the structure.

The trench should provide an effective trench plug that extends at least 5 feet from the face of the building exterior. The plug material should consist of cementitious flowable fill or low permeability clay. The trench plug material should be placed to surround the utility line. If used, the clay trench plug material should be placed and compacted to comply with the water content and compaction recommendations for structural fill stated previously in this report.

Grading and Drainage

All grades must provide effective drainage away from the structure during and after construction and should be maintained throughout the life of the structure. Accumulation of water adjacent to the structure could contribute to significant moisture increases in the subgrade soils and subsequent softening/settlement or expansion/heave, which could result in soil movements greater than those discussed in this report.

Earthwork Construction Considerations

Upon completion of filling and grading, care should be taken to maintain the subgrade water content prior to construction of grade-supported improvements such as 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.

Facilities | Environmental | Geotechnical | Materials 9

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 or other activities resulting in ground disturbance have the potential to affect adjoining properties and structures. Our scope of services does not include review of available final grading information or consider potential temporary grading performed by the contractor for potential effects such as ground movement beyond the project limits. A preconstruction/ precondition survey should be conducted to document nearby property/infrastructure prior to any site development activity. Excavation or ground disturbance activities adjacent or near property lines should be monitored or instrumented for potential ground movements that could negatively affect adjoining property and/or structures.

Construction Observation and Testing

The earthwork efforts should be observed by the Geotechnical Engineer (or others under their direction). Observation should include documentation of adequate removal of surficial materials (vegetation, topsoil, and pavements), evaluation and remediation of existing fill materials, as well as proofrolling and mitigation of unsuitable areas delineated by the proofroll.

Each lift of compacted fill should be tested, evaluated, and reworked, as necessary, as recommended 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 stairwell area. Where not specified by local ordinance, one density and water content test should be performed for every 50 linear feet of compacted utility trench backfill and a minimum of one test performed for every 12 vertical inches of compacted backfill.

In areas of foundation excavations, the bearing subgrade should be evaluated by the

Geotechnical Engineer. If unanticipated conditions are observed, 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.

Facilities | Environmental | Geotechnical | Materials 10

Mat Foundations

If the site has been prepared in accordance with the requirements noted in Earthwork, the following design parameters are applicable for mat foundations supporting the stairwell.

Design Parameters

Item Description

Maximum Net Allowable

Bearing Pressure

1,000 psf

Required Bearing Stratum 2,3

Native very stiff lean clay or shaley lean clay bearing approximately 3.5 feet below the ground surface

Estimated Modulus of

Subgrade Reaction, k

100 pci

Corrected or Design

Modulus of Subgrade

Reaction, kc 𝑘𝑐 = 𝑘

𝐵

Allowable Coefficient of

Sliding Friction

0.2

Frost Depth 18 inches

Minimum Embedment below

Finished Subgrade

24 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 foundation base elevation.

This value is applicable to sustained loads. An appropriate factor of safety has been applied. The bearing pressure can be increased by 1/3 for transient loads.

2. Unsuitable or soft soils should be over-excavated and replaced. We recommend evaluating the bearing materials by performing hand augers, T-probes, calibrated penetrometer tests, and/or dynamic cone penetrometer (DCP) tests in the foundation excavations. When DCP tests are used to evaluate the suitability of the bearing materials, they should be performed at the base of the foundation excavation and at every 12 inches to a depth equal to the

Facilities | Environmental | Geotechnical | Materials 11 foundation width. However, in no case should the suitability of the bearing materials be evaluated to a depth that is less than 3 feet below the base of foundations. If unsuitable soil is present, the excavation should be extended until suitable material is encountered. Foundations could bear on suitable material or on lean concrete backfill or engineered backfill placed in the excavations as outlined the following report section.

3. Due to access limitations, the borings that were completed at the time of this investigation were adjacent to the existing parking garage. Therefore, the very stiff lean clay or shaley lean clay may be deeper than 3.5 feet within the exact footprint of the proposed stairwell.

4. Modulus of subgrade reaction (k) is an estimated value based upon our experience with the subgrade condition. This value is based on a 1 foot by 1 foot plate. For large area loads, the modulus of subgrade reaction would be lower.

5. It is common to reduce the k value to account for dimensional effects of large, loaded areas. kc is the corrected or design modulus value. B is the foundation width.

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 is necessary to minimize the effects of frost and/or seasonal moisture content variations. We recommend the perimeter edge of the foundations for the plant building and pump building to bear at least 24 inches below finished subgrade.

8. Differential settlement between the proposed stairwell and the existing parking garage is expected to approach the magnitude of the total settlement of the stairwell. Expansion joints should be provided between the existing parking garage and the new stairwell to accommodate differential movements between the structures.

Foundation Construction Considerations

As noted in Earthwork, the foundation excavations should be evaluated under the observation 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. If the soils at the bearing level become excessively dry, disturbed, saturated, or frozen, the affected soil should be removed prior to placing concrete. If the excavations must remain open overnight or for an extended period of time, placement of a lean concrete mud-mat over the bearing soils should be considered.

Facilities | Environmental | Geotechnical | Materials 12

The bearing materials at the base of each foundation excavation should be evaluated by a representative of the Geotechnical Engineer.

If unsuitable bearing soils are observed at the base of the planned foundation excavation, the excavation should be extended deeper to suitable soils, and the foundations could bear directly on these soils at the lower level or on lean concrete backfill placed in the excavations. The lean concrete replacement zone is illustrated on the sketch below.

Overexcavation for structural fill placement below foundations should be conducted as shown below. The overexcavation should be backfilled up to the foundation base elevation, with low plasticity cohesive materials placed, as recommended in the

Earthwork section.

Facilities | Environmental | Geotechnical | Materials 13

Helical Piles

Helical piles can also be considered to support the stairwell. Because helical steel piles are a proprietary foundation system, we recommend the boring logs included in this report along with the foundation loads be provided to the helical pile contractor for their use in designing the piles.

Floor Slabs

Design parameters for floor slabs assume the requirements for Earthwork have been followed. Specific attention should be given to positive drainage away from the structure and positive drainage of the aggregate base beneath the floor slab.

Floor Slab Design Parameters

Item Description

Floor Slab

Support1

At least 1.5 feet of low volume change (LVC) material prepared in accordance with Earthwork

Estimated Modulus of Subgrade

Reaction 2

100 pounds per square inch per inch (psi/in) for point loads

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.

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, when the project includes humidity-controlled areas, 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 contraction 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 be sealed with a waterproof, non-extruding compressible compound specifically recommended for heavy duty concrete pavement and wet environments.

Facilities | Environmental | Geotechnical | Materials 14

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.

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 observe 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

Structures with unbalanced backfill levels on opposite sides should be designed for earth pressures at least equal to values 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 in the diagram below. Active earth pressure is commonly used for design of free-standing cantilever retaining walls and assumes wall movement is acceptable. The “at-rest” condition assumes no wall movement and is commonly used for design of basement walls, loading dock walls, or other walls restrained at the top. The recommended design lateral earth pressures do not include a factor of safety and do not provide for possible hydrostatic pressure on the walls (unless stated).

Facilities | Environmental | Geotechnical | Materials 15

Lateral Earth Pressure Design Parameters

Earth

Pressure

Condition 1

Coefficient for

Backfill Type 2

Surcharge

Pressure 3 p1 (psf)

Equivalent Fluid Pressures

(psf) 2,4

Unsaturated 5 Submerged 5

Active (Ka) Granular - 0.33

Fine Grained - 0.42

(0.33)S

(0.42)S

(45)H

(50)H

(85)H

(85)H

At-Rest (Ko) Granular - 0.50

Fine Grained - 0.59

(0.50)S

(0.59)S

(65)H

(70)H

(95)H

(95)H

1. For active earth pressure, wall must rotate about base, with top lateral movements 0.002 H to 0.004 H, where H is wall height. For passive earth pressure, wall must move horizontally to mobilize resistance. Fat clay or other expansive soils should not be used as backfill behind the wall.

2. Uniform, horizontal backfill, with a maximum unit weight of 120 pcf for cohesive soils and 130 pcf for granular soils.

3. Uniform surcharge, where S is surcharge pressure.

4. Loading from heavy compaction equipment is not included.

5. To achieve “Unsaturated” conditions, follow guidelines in Subsurface Drainage for Below-Grade Walls below. “Submerged” conditions are recommended when drainage behind walls is not incorporated into the design.

Backfill placed against structures should consist of granular soils or low plasticity cohesive soils. 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 degrees from vertical for the active case.

Footings, floor slabs or other loads bearing on backfill behind walls may have a significant influence on the lateral earth pressure. Placing footings within wall backfill and in the zone of active soil influence on the wall should be avoided unless structural analyses indicate the wall can safely withstand the increased pressure.

Facilities | Environmental | Geotechnical | Materials 16

The lateral earth pressure recommendations given in this section are applicable to the design of rigid retaining walls subject to slight rotation, such as cantilever, or gravity type concrete walls. These recommendations are not applicable to the design of modular block - geogrid reinforced backfill walls (also termed MSE walls). Recommendations covering these types of wall systems are beyond the scope of services for this assignment. However, we would be pleased to develop a proposal for evaluation and design of such wall systems upon request.

Subsurface Drainage for Below-Grade Walls

A perforated rigid plastic drain line installed behind the base of walls and extends below adjacent grade is recommended to prevent hydrostatic loading on the walls. The invert of a drain line around a below-grade building area or exterior retaining wall should be placed near foundation bearing level. The drain line should be sloped to provide positive gravity drainage to daylight or to a sump pit and pump. The drain line should be surrounded by clean, free-draining granular material having less than 5% passing the

No. 200 sieve, such as No. 57 aggregate. The free-draining aggregate should be encapsulated in a filter fabric. The granular fill should extend to within 2 feet of final grade, where it should be capped with compacted cohesive fill to reduce infiltration of surface water into the drain system.

As an alternative to free-draining granular fill, a prefabricated drainage structure may be used. A prefabricated drainage structure is a plastic drainage core or mesh which is covered with filter fabric to prevent soil intrusion and is fastened to the wall prior to placing backfill.

General Comments

Our analysis and opinions are based upon our understanding of the project, the geotechnical conditions in the area, and the data obtained from our site exploration.

Facilities | Environmental | Geotechnical | Materials 17

Variations will occur between exploration point locations or due to the modifying effects of construction or weather. The nature and extent of such variations may not become evident until during or after construction. Terracon should be retained as the

Geotechnical Engineer, where noted in this report, to provide observation and testing services during pertinent construction phases. If variations appear, we can provide further evaluation and supplemental recommendations. If variations are noted in the absence of our observation and testing services on-site, we should be immediately notified so that we can provide evaluation and supplemental recommendations.

Our Scope of Services does not include either specifically or by implication any environmental or biological (e.g., mold, fungi, bacteria) assessment of the site or identification or prevention of pollutants, hazardous materials or conditions. If the owner is concerned about the potential for such contamination or pollution, other studies should be undertaken.

Our services and any correspondence are intended for the sole benefit and exclusive use of our client for specific application to the project discussed and are accomplished in accordance with generally accepted geotechnical engineering practices with no third-party beneficiaries intended. Any third-party access to services or correspondence is solely for information purposes to support the services provided by Terracon to our client. Reliance upon the services and any work product is limited to our client and is not intended for third parties. Any use or reliance of the provided information by third parties is done solely at their own risk. No warranties, either express or implied, are intended or made.

Site characteristics as provided are for design purposes and not to estimate excavation cost. Any use of our report in that regard is done at the sole risk of the excavating cost estimator as there may be variations on the site that are not apparent in the data that could significantly affect excavation cost. Any parties charged with estimating excavation costs should seek their own site characterization for specific purposes to obtain the specific level of detail necessary for costing. Site safety and cost estimating including excavation support and dewatering requirements/design are the responsibility of others.

Construction and site development have the potential to affect adjacent properties. Such impacts can include damages due to vibration, modification of groundwater/surface water flow during construction, foundation movement due to undermining or subsidence from excavation, as well as noise or air quality concerns. Evaluation of these items on nearby properties are commonly associated with contractor means and methods and are not addressed in this report. The owner and contractor should consider a preconstruction/precondition survey of surrounding development. If changes in the nature, design, or location of the project are planned, our conclusions and recommendations shall not be considered valid unless we review the changes and either verify or modify our conclusions in writing.

Figures

Contents:

GeoModel

1,205

1,210

1,215

1,220

1,225

1,230

1,235

1,240

1,245

1,250

E L E

V A

T

IO

N

M S

L

(f e e t)

Layering shown on this figure has been developed by the geotechnical engineer for purposes of modeling the subsurface conditions as required for the subsequent geotechnical engineering for this project.

Numbers adjacent to soil column indicate depth below ground surface.

NOTES:

B-1

B-2

Legend

This is not a cross section. This is intended to display the Geotechnical Model only. See individual logs for more detailed conditions.

GeoModel

N Kelley Avenue and NE 13th Street | Oklahoma City, Oklahoma

Terracon Project No. 03235201

VAMC Parking Garage Stair Tower

4701 N Stiles Ave

Oklahoma City, OK

Concrete Lean Clay

Shale Asphalt

Poorly-graded Gravel with Silt

Model Layer Layer Name General Description

1 Lean Clay (CL) and Shaley Lean Clay (CL) with varying amounts of sand

3 Weathered Shale

2 Poorly Graded Gravel with Silt (GP-GM)

Clay

Bedrock

Gravel

3.5

13.5

Attachments

Exploration and Testing Procedures

Field Exploration

Number of Borings Approximate Boring

Depth (feet) Location

2 29 Adjacent to the new stairwell renovation area

Boring Layout and Elevations: Terracon personnel provided the boring layout.

Coordinates were obtained with an AtlasLink Hemisphere GPS device. The ground surface elevations at the boring locations ranged from 1234.5 to 1245.0 feet. We rounded the elevations on the boring log to the nearest one-half foot. Consider the location and elevation of the boring accurate only to the degree implied by the methods used to make these measurements.

Subsurface Exploration Procedures: We advanced the borings with a truck-mounted rotary drill rig using continuous flight augers (solid stem and/or hollow stem, as necessary, depending on soil conditions). Four samples were obtained in the upper 10 feet of each boring and at intervals of 5 feet thereafter. In the split-barrel sampling procedure, a standard 2-inch outer diameter split-barrel sampling spoon was driven into the ground by a 140-pound automatic hammer falling a distance of 30 inches. The number of blows required to advance the sampling spoon the last 12 inches of a normal

18-inch penetration is recorded as the Standard Penetration Test (SPT) resistance value.

The SPT resistance values, also referred to as N-values, are indicated on the boring logs at the test depths. We observed and recorded groundwater levels during drilling and sampling. For safety purposes, all borings were backfilled with auger cuttings after their completion. As required by the State of Oklahoma, any borings deeper than 20 feet, or borings which encounter groundwater or contaminated materials must be grouted or plugged in accordance with Oklahoma State statutes. One boring log must also be submitted to the Oklahoma Water Resources Board for each 10 acres of project site area. Terracon grouted the borings and submitted logs in order to comply with the

Oklahoma Water Resources Board requirements. Pavements were patched with cold-mix asphalt and/or pre-mixed concrete, as appropriate.

The sampling depths, penetration distances, and other sampling information was recorded on the field boring logs. The samples were placed in appropriate containers and taken to our soil laboratory for testing and classification by a Geotechnical Engineer. Our exploration team prepared field boring logs as part of the drilling operations. These field logs included visual classifications of the materials observed during drilling and our interpretation of the subsurface conditions between samples. Final boring logs were prepared from the field logs. The final boring logs represent the Geotechnical Engineer's interpretation of the field logs and include modifications based on observations and tests of the samples in our laboratory.

Laboratory Testing

The project engineer reviewed the field data and assigned laboratory tests. The laboratory testing program included the following types of tests:

■ Moisture Content

■ Atterberg Limits

■ Soluble sulfate content

The laboratory testing program often included examination of soil samples by an engineer. Based on the results of our field and laboratory programs, we described and classified the soil samples in accordance with the Unified Soil Classification System.

Rock classification was conducted using locally accepted practices for engineering purposes; petrographic analysis may reveal other rock types. Rock core samples typically provide an improved specimen for this classification. Boring log rock classification was determined using the Description of Rock Properties.

Site Location and Exploration Plans

Site Location Plan

Exploration Plan

Note: All attachments are one page unless noted above.

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Site Location

DIAGRAM IS FOR GENERAL LOCATION ONLY, AND IS NOT INTENDED FOR CONSTRUCTION PURPOSES MAP PROVIDED BY MICROSOFT BING MAPS

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Exploration Plan

DIAGRAM IS FOR GENERAL LOCATION ONLY, AND IS NOT INTENDED FOR CONSTRUCTION PURPOSES MAP PROVIDED BY MICROSOFT BING MAPS

Exploration and Laboratory Results

Boring Logs (B-1 and B-2)

1234.2

1228.5

1220.5

1205.5

-Approximately 4" of Portland Cement Concrete LEAN CLAY (CL), trace sand, red, stiff

-very stiff below 3.5'

SHALEY LEAN CLAY (CL), red, hard

WEATHERED SHALE, red, soft

-hard below 28.5' Boring Terminated at 29 Feet

Boring Log No. B-1

W at er L ev el

O bs er va tio ns

D ep th

Ft

Facilities | Environmental | Geotechnical | Materials

G ra p h ic

L o g

M o d el

L ay er

13.3

13.6

14.2

14.0

12.5

11.7

11.5

8.7

32-16-16

0.3

6.0

14.0

29.0

5-7-7 N=14

6-11-16 N=27

12-21-31 N=52

11-34-39 N=73

25-50/6"

50/5"

50/6"

50/1"

N Kelley Avenue and NE 13th Street | Oklahoma City, Oklahoma

Terracon Project No. 03235201 Oklahoma City, OK

4701 N Stiles Ave

Drill Rig

Hammer Type Automatic

Driller

RP

Logged by

AG

Boring Started 11-09-2024

Boring Completed 11-09-2024

Abandonment Method Boring backfilled with soil cuttings and bentonite chips upon completion.

Advancement Method Power Auger

Notes

Water Level Observations No free water observed

See Exploration and Testing Procedures for a description of field and laboratory procedures used and additional data (If any).

See Supporting Information for explanation of symbols and abbreviations.

VAMC Parking Garage Stair Tower

S am pl e

T yp e

Pe rc en t

Fi n es

W at er C o n te n t

Elevation: 1234.5 (Ft.) +/-

Atterberg Limits

LL-PL-PI

See Exploration PlanLocation:

Latitude: 35.4827° Longitude: -97.4951°

Depth (Ft.)

R ec o ve ry

In

Fi el d T es t

R es u lt s

1244.5

1241.5

1231.5

-Approximately 6" of Asphalt POORLY GRADED GRAVEL WITH SILT (GP-GM), gray, very dense

SHALEY LEAN CLAY (CL), red, very stiff

-hard below 6'

WEATHERED SHALE, red, soft

-hard below 18.5'

-soft to moderately hard below 23.5'

Boring Terminated at 29 Feet

Boring Log No. B-2

W at er L ev el

O bs er va tio ns

D ep th

Ft

Facilities | Environmental | Geotechnical | Materials

G ra p h ic

L o g

M o d el

L ay er

3.7

18.1

13.8

14.3

10.0

10.9

12.7

11.6

26-15-11

0.5

3.5

13.5

29.0

50/3"

8-10-16 N=26

16-26-37 N=63

25-40-45 N=85

50/6"

50/1"

27-50/4"

50/3"

N Kelley Avenue and NE 13th Street | Oklahoma City, Oklahoma

Terracon Project No. 03235201 Oklahoma City, OK

4701 N Stiles Ave

Drill Rig

Hammer Type Automatic

Driller

RP

Logged by

AG

Boring Started 11-09-2024

Boring Completed 11-09-2024

Abandonment Method Boring backfilled with soil cuttings and bentonite chips upon completion.

Advancement Method Power Auger

Notes

Water Level Observations No free water observed

See Exploration and Testing Procedures for a description of field and laboratory procedures used and additional data (If any).

See Supporting Information for explanation of symbols and abbreviations.

VAMC Parking Garage Stair Tower

S am pl e

T yp e

Pe rc en t

Fi n es

W at er C o n te n t

Elevation: 1245.0 (Ft.) +/-

Atterberg Limits

LL-PL-PI

See Exploration PlanLocation:

Latitude: 35.4829° Longitude: -97.4945°

Depth (Ft.)

R ec o ve ry

In

Fi el d T es t

R es u lt s

Supporting Information

General Notes

Unified Soil Classification System

Description of Rock Properties

Standard Penetration Test

Facilities | Environmental | Geotechnical | Materials

> 8,000

4,000 to 8,000

2,000 to 4,000

1,000 to 2,000

500 to 1,000 less than 500

Unconfined Compressive Strength Qu (psf)

VAMC Parking Garage Stair Tower

N Kelley Avenue and NE 13th Street | Oklahoma City, Oklahoma

Terracon Project No. 03235201 4701 N Stiles Ave

Oklahoma City, OK

N

(HP)

(T)

(DCP)

UC

(PID)

(OVA)

Standard Penetration Test Resistance (Blows/Ft.)

Hand Penetrometer

Torvane

Dynamic Cone Penetrometer

Unconfined Compressive Strength

Photo-Ionization Detector

Organic Vapor Analyzer

Water Level After a Specified Period of Time

Water Level After a Specified Period of Time

Cave In Encountered

Water Level Field Tests

Water Initially Encountered

Sampling

Water levels indicated on the soil boring logs are the levels measured in the borehole at the times indicated. Groundwater level variations will occur over time. In low permeability soils, accurate determination of groundwater levels is not possible with short term water level observations.

General Notes

Location And Elevation Notes

Exploration point locations as shown on the Exploration Plan and as noted on the soil boring logs in the form of Latitude and Longitude are approximate. See Exploration and Testing Procedures in the report for the methods used to locate the exploration points for this project. Surface elevation data annotated with +/- indicates that no actual topographical survey was conducted to confirm the surface elevation. Instead, the surface elevation was approximately determined from topographic maps of the area.

Soil classification as noted on the soil boring logs is based Unified Soil Classification System. Where sufficient laboratory data exist to classify the soils consistent with ASTM D2487 "Classification of Soils for Engineering Purposes" this procedure is used. ASTM D2488 "Description and

Identification of Soils (Visual-Manual Procedure)" is also used to classify the soils, particularly where insufficient laboratory data exist to…