A.01.30_17R0005_Columbia_VAMC_Parking_Garage_Geotechnical_Report_7-18-2017.PDF

Geotechnical Engineering Report W. J. B. Dorn VA Medical Center - Parking Garage

6439 Garners Ferry Road Columbia, South Carolina

July 13, 2015 Terracon Project No. 73155038

Prepared for:

Guidon Design

Indianapolis, Indiana

Prepared by:

Terracon Consultants, Inc.

Columbia, South Carolina

Terracon Consul tants, Inc. 521 Clemson Road Columbia, South Carol ina 29229 P [803] 741 9000 F [803] 741 9900 terracon.com

July 13, 2015

Guidon Design 905 N. Capital Avenue, Suite 100 Indianapolis, Indiana 46204

Attn: Ms. Stacey Paul, PE

Re: Geotechnical Engineering Report W. J. B. Dorn VA Medical Center - Parking Garage Columbia, South Carolina Terracon Project No. 73155038

Dear Ms. Paul:

Terracon Consultants, Inc. (Terracon) has completed the geotechnical engineering services for the above referenced project. This study was performed in general accordance with our Proposal No. P73150144 dated April 1, 2015 and authorized on June 24, 2015.

This report presents the findings of the subsurface exploration and provides geotechnical recommendations concerning earthwork and the design and construction of foundations, retaining walls, and floor slabs for the proposed project.

We appreciate the opportunity to be of service to you on this project. Materials testing services are provided by Terracon. We would be pleased to discuss these services with you. If you have any questions concerning this report or we may be of further service, please contact us.

Sincerely, Terracon Consultants, Inc.

Kenneth J. Zur, P.E. Phillip A. Morrison, P.E.

Senior Geotechnical Engineer Geotechnical Department Manager SC Registration No. 25833 SC Registration No. 17275

Attachments:

Copies: Addressee (1 via email) File (1)

TABLE OF CONTENTS

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Page EXECUTIVE SUMMARY ............................................................................................ i

1.0 INTRODUCTION

2.0 PROJECT DESCRIPTION

2.1 Project Description

2.2 Site Location and Description

3.0 SUBSURFACE CONDITIONS

3.1 Geology

3.2 Typical Subsurface Profile

3.3 In-Situ Pressuremeter Testing

3.4 Groundwater Conditions

4.0 GEOTECHNICAL SEISMIC EVALAUATION

4.1 Shear Wave Velocity Profile

4.2 South Carolina Seismicity

4.3 South Carolina Seismic Sources

4.4 Seismic Evaluation

4.4.1 Site Specific Response Analysis

4.4.2 Site Response Analysis and Computed Results

5.0 RECOMMENDATIONS FOR DESIGN AND CONSTRUCTION

5.1 Geotechnical Considerations

5.2 Earthwork

5.2.1 Site Preparation

5.2.2 Subgrade Preparation

5.2.3 Material Types

5.2.4 Compaction Requirements

5.2.5 Temporary Excavations

5.2.6 Construction Considerations

5.3 Foundation Systems

5.3.1 Soil Supported Spread Footings

5.3.2 Construction Recommendations

5.3.3 Shallow Foundations (Stone Columns)

5.3.4 Foundation Considerations

5.4 Floor Slabs

5.4.1 Design Recommendations

5.4.2 Construction Considerations

5.5 Lateral Earth Pressures

5.6 Soil Corrosion Considerations

6.0 GENERAL COMMENTS

APPENDIX A – FIELD EXPLORATION

Exhibit A-1 ............................... Site Location Map Exhibit A-2 ............................... Boring Location Plan Exhibit A-3 ............................... Field Exploration Description Exhibit A-4 ............................... Shear Wave Velocity Profile Exhibit A-5 ............................... Site Specific Seismic Response Spectrum Exhibits A-6 to A-14 ................. Boring Logs B-1 through B-9 Exhibits A-15 to A-21 ............... Pressuremeter Test Results

APPENDIX B – LABORATORY TESTING

TABLE OF CONTENTS

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Exhibit B-1 ............................... Laboratory Testing Description Exhibit B-2 ............................... Summary of Laboratory Data Exhibit B-3 to B-8 ..................... Laboratory Test Results Exhibit B-9 ............................... Analytical Test Results

APPENDIX C – SUPPORTING DOCUMENTS

Exhibit C-1 ............................... General Notes Exhibit C-2 ............................... Unified Soil Classification System

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EXECUTIVE SUMMARY

A geotechnical investigation has been performed for a proposed parking garage to be constructed at W.J.B. Dorn VA Medical Center in Columbia, South Carolina. Nine (9) borings, designated B-1 through B-9, were performed to depths ranging from approximately 25 feet to 75 feet below the existing ground surface. Based on the information obtained from our subsurface exploration, the site can be developed for the proposed project. The following geotechnical considerations were identified:

n The subsurface soil conditions encountered within the footprint of the proposed parking garage generally consisted of up to 5-½ feet of undocumented fill followed by sandy silt/silty sand to silty/sandy clay that extended to depths ranging from 37 feet to 42 feet.

The silts, sands and clays grade into a lean to fat clay that extends to the termination depth of the deepest Boring (B-2) at a depth of 75 feet.

n Groundwater was not recorded at the boring locations at the time of drilling due to the method of advancing the borings. When checked after a stabilization period (of 1 to 3 days), groundwater was not encountered to depths of 25 to 49 feet below the existing ground surface (cave-in depths).

n Based on the 2012 International Building Code and an average weighted shear wave velocity of 1,365 feet per second, the seismic site class for this site is “C”. Utilizing the mapped parameters from IBC 2012 and ASCE 7-10, a Seismic Design Category (SDC) of C was determined. A Site Specific Seismic Evaluation (SSSE) was performed which allowed the SDC to be modified from “C” to “B”.

n Based on the provided structural loads, subsurface soil conditions and using an allowable bearing capacity of 3,500 psf, total settlements for shallow spread footings are estimated to range from 1 to 1-½ inches with differential settlements approaching 50 percent of the total. To provide the noted bearing pressure and limit the total settlement to 1-½ inches, it will be necessary repair any soft foundation soils encountered at or near the bearing elevation of many foundations elements. Based on the boring data, we estimate about 45 percent of the foundations may require repair.

n Alternatively, shallow foundations can be supported on the existing soil column improved by stone columns. With their installation, shallow foundations can typically be designed with allowable contact pressures on the order of 5,000 to 7,000 psf without the need to repair the foundation soils.

n Close monitoring of the construction operations discussed herein will be critical in achieving the design foundation support. We therefore recommend that the Terracon be retained to monitor site and foundation construction for this project.

This summary should be used in conjunction with the entire report for design purposes. It should be recognized that details were not included or fully developed in this section, and the report must be read in its entirety for a comprehensive understanding of the items contained herein. The section titled GENERAL COMMENTS should be read for an understanding of the report limitations.

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GEOTECHNICAL ENGINEERING REPORT

W.J.B. DORN VA MEDICAL CENTER - PARKING GARAGE

COLUMBIA, SOUTH CAROLINA

Terracon Project No. 73155038 July 13, 2015

1.0 INTRODUCTION

This report presents the results of our geotechnical engineering services performed for the proposed parking garage to be located in Columbia, South Carolina. The purpose of these services is to provide information and geotechnical engineering recommendations relative to:

n subsurface soil conditions n groundwater conditions n earthwork n foundation design and construction n seismic considerations n retaining walls n slab-on-grade design and construction n other design considerations

Our geotechnical engineering scope of work for this project included the advancement of nine

(9) soil test borings to depths ranging from approximately 25 to 75 feet below existing site grades. At three of the boring locations, in-situ pressuremeter testing was performed. In addition to soil borings, geophysical testing was performed to develop the shear wave velocity profile for the site.

Logs of the borings, shear wave velocity profile, the Site Location Map and the Boring Location Plan are included in Appendix A of this report. The results of the laboratory testing performed on select soil samples obtained from the site during the field exploration are included in Appendix B of this report. Descriptions of the field exploration and laboratory testing are included in their respective appendices.

2.0 PROJECT DESCRIPTION

2.1 Project Description

ITEM DESCRIPTION

Site Location Refer to the Site Location Plan (Exhibit A-1 in Appendix A).

Structure2 The garage will have three supported levels above the at-grade level. The garage will have a footprint of 124-feet by 318-½-feet.

Building construction2 The parking garage will be a pre-cast structure with bays on the order of 36 feet by 62 feet

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ITEM DESCRIPTION

Finished floor elevation2 The average finished floor elevation (FFE) is currently set at Elevation 249.8± feet MSL.

Structural loads1

Column loads:

n 600 to 1,060 kips (ultimate) n 480 to 830 kips (service) Wall loads:

n 34.4 to 36.2 kips/foot (ultimate) n 26.3 to 28.1 kips/foot (service) Slab-on-grade floor loads are expected to approach 100 psf.

Maximum allowable settlement1

Total: 1-½-inches Differential: ¾ inch between columns

Grading Based on currently available information, we anticipate cuts and fills of up to 2 or 4 feet will be necessary to establish nominal construction grade.

Below grade areas A 4- to 5-foot deep elevator pit is expected.

1. Based on information provided by Cal Walker, Inc.

2. Based on 35% structural and architectural design drawings.

2.2 Site Location and Description

ITEM DESCRIPTION

Location

W.J.B. Dorn VA Medical Center is located at 6439 Garners Ferry Road in Columbia, South Carolina. The parking garage will be located in an existing parking lot located southwest of Building 106 (Mental Health – Dermatology).

Latitude and Longitude1 33.9752° N, 80.9620° W

Existing improvements

The majority of the site is currently an at-grade parking lot and loop road around the hospital campus. The remainder of the site consists of a landscaped berm that separates Byron Road from residential areas further to the west.

Current ground cover Away from the noted berms, the footprint of the proposed parking garage is currently asphalt paved with landscaped medians.

Existing topography2 The construction area is relatively flat with surface elevations of 247 to 248 feet, except at the berm along Bryon Street which was generally 4 to 7 feet higher.

Site history

Based on a review of historical imagery (1939) of the area, it appears a portion of the area proposed for a new parking garage was occupied by a baseball diamond and associated structures. In a later dated image (1959), these structures had been removed.

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ITEM DESCRIPTION

1 Taken as the approximate center of the parking garage.

2 Survey information provided by Woolpert.

3.0 SUBSURFACE CONDITIONS

3.1 Geology

The site is located in the upper Coastal Plain physiographic province of South Carolina. The Coastal Plain is a wedge-shaped cross-section of water and wind deposited soil. Its thickness ranges from a featheredge at the surface contact of the Piedmont (Fall Line) to several thousand feet at the present day coastline. The sediments range in age from the Cretaceous and Tertiary periods at the contact with the bedrock to the recent period at the present coastline. The sediments include clays, silts, sands, and gravels, as well as organics.

Fill soils are those soils that have been placed or reworked in conjunction with past construction grading or farming. Fill can be composed of different soil types from various sources and can contain debris from building demolition, organics, topsoil, trash, etc. The engineering properties of the fill depend primarily on its composition, density, and moisture content.

3.2 Typical Subsurface Profile

Specific conditions encountered at each boring location are indicated on the individual boring logs included in Appendix A of this report. Stratification boundaries on the boring logs represent the approximate location of changes in soil types; in situ, the transition between materials may be gradual. Based on the results of the borings, subsurface conditions on the project site can be generalized as follows:

Description Approximate Depth to Bottom of Stratum (feet) Material Encountered Consistency/Density

Surface 1-½ to 2-½ inches Topsoil/Asphaltic Concrete n/a

Stratum #11 3 to 5-½ Fill - sandy clay Stiff to hard

Stratum #2 37 to 42 Silty sand to sandy silt/clay Medium dense/ soft to hard

Stratum #3 Termination depth of boring Lean to fat clay Very stiff to hard

1 Fill material encountered in Borings B-1, B-2, B-4, B-6, B-8, and B-9.

Laboratory tests were conducted on selected soil samples. The test results are included in Appendix B and presented graphically on the Boring Logs presented in Appendix A.

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Additionally, testing specific to corrosion (pH, resistivity, etc.) was performed on select soils samples collected from Borings B-1 and B-6. The results of all analytical laboratory testing are also included in Appendix B.

3.3 In-Situ Pressuremeter Testing

In-situ testing was performed to better estimate the stress/strain behavior of the site soils utilizing the Roctest TEXAM Pressuremeter. A series of pressuremeter tests was performed at Borings B-3, B-5, and B-7 at depths ranging from 5 to 30 feet below the existing ground surface. The results of the pressuremeter testing are summarized in the following table. The results are also presented graphically in Appendix A. The pressuremeter testing for this project resulted in an E:N ratio (soil modulus to blow count) ranging from 4 to 10 with an overall average of approximately 8. Values of 4 or 6 are considered typical for most area soils in the absence of such site specific data.

Pressuremeter Test Results Boring

No.

Depth

(ft)

EP

psi (ksf) Depth

(ft)

EP

psi (ksf) Depth

(ft)

EP

psi (ksf) B-3 8 5,306 (764) 18 3,570 (514) 29 3,378 (486)

B-5 4 3,257 (469)

B-7 8 3,961 (570) 16 1,821 (262) 30 2,634 (379)

3.4 Groundwater Conditions

Due to the method of drilling (i.e. mud rotary) groundwater readings at the time of drilling was not measured. When checked a minimum of 24 hours after drilling, groundwater was not encountered to depths of 25 to 49 feet. These observations represent groundwater conditions at the time of the field exploration, and may not be indicative of other times, or at other locations.

Groundwater level fluctuations occur due to seasonal variations in the amount of rainfall, runoff and other factors not evident at the time the fieldwork was performed. Therefore, groundwater levels during construction or at other times in the life of the structure may be higher or lower than the levels discussed herein. The possibility of groundwater level fluctuations should be considered when developing the design and construction plans for the project. The groundwater surface should be checked prior to construction to assess its effect on grading activities and other construction activities.

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4.0 GEOTECHNICAL SEISMIC EVALAUATION

4.1 Shear Wave Velocity Profile

Based on the results of the geophysical testing results (ReMi testing) performed for the W.J.B.

Dorn VA Medical Center Parking Garage and considering the soil test boring data, the following average weighted shear wave velocity was utilized in our evaluation:

Test Average Weighted Shear Wave Velocity (ࢂഥ࢙)1

REMI Array 1,365 ft/s

1. Calculated in accordance with IBC 2012/ASCE 7-10

4.2 South Carolina Seismicity

Even though seismically active areas in the United States are generally considered to be in California and Western United States, historical records indicate that there have been major earthquake events in Central and Eastern United States (CEUS) that have not only been of equal or greater magnitude but that have occurred over broader areas of the CEUS. The United States Geologic Survey (USGS) indicates earthquakes that have caused damage within the United States between 1750 and 1996. Of particular interest to South Carolina is the 1886 earthquake in Charleston, South Carolina that has been estimated to have a Moment Magnitude (Mw) of at least 7.3.1

4.3 South Carolina Seismic Sources

The most severe earthquake to occur in South Carolina’s recorded history occurred near Charleston in 1886. It was one of the largest earthquakes to affect the Eastern United States in historical times. The Mw of this earthquake has been estimated to range between 7.0 and

7.5. It is typically referred to have a Mw of 7.3. The faulting source that was responsible for the 1886 Charleston earthquake remains uncertain to this date.

Large magnitude earthquake events with the potential to occur in South Carolina are considered characteristic earthquakes. These earthquakes are modeled as a combination of fault sources and a seismic Area Source. The SC Seismic Hazard Study used the 1886 Earthquake fault source, also known as the Middleton Place seismic zone, and the “Zone of River Anomalies” (ZRA) fault source. For the 1886 Earthquake fault source, it assumed that rupture occurred on the NE trending “Woodstock” fault and on the NW trending “Ashley River” fault. The 1886 Earthquake fault source is modeled as three independent parallel faults.

1 South Carolina Department of Transportation Geotechnical Design Manual 2010.

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Recent studies (Marple and Talwani, 1993, 2000)2 suggest that the “Woodstock” fault may be a part of a larger NE trending fault system that extends to North Carolina and possibly Virginia, referred to in the literature as the “East Coast Fault System”. The ZRA fault source is the term used for the portion of the “East Coast Fault System” that is located within South Carolina.

The ZRA fault system is modeled by a 145-mile long fault with a NE trend. The characteristic seismic Area Source is the same as is used in the 1996 National Seismic Hazard Maps. It models a network of individual faults no greater than 46 miles in length within the Lower Coastal Plain.

4.4 Seismic Evaluation

4.4.1 Site Specific Response Analysis

In order to model the seismic site response, a site specific response analysis has been conducted to define the Maximum Considered Earthquake (MCE) and Design Basis Earthquake (DBE) for a 2% probability of exceedance in 50 years (2500-year return period).

The site specific response analysis was conducted in general accordance with Section 21.2 of ASCE 7-10.

4.4.2 Site Response Analysis and Computed Results

The site response analysis was conducted using the computer program EZ-FRISK commercially distributed by Risk Engineering. EZ-FRISK calculates the deterministic and probabilistic seismic hazard based on seismic sources and attenuation relationships. For the W.J.B Dorn VA Medical Center, the following seismic sources and attenuation relationships were considered:

Seismic Sources n CEUS Gridded – AB n CEUS Gridded – J n New Madrid – Composite n Charleston Composite n Cheraw Fault

Attenuation Relationships n Toro (1999) Midcontinent - USGS 2008 MbLg n Frankel (1996) USGS 2008 Truncated MbLg - AB n Campbell (2003) USGS 2008 MbLg - AB n Atkinson-Boore (2006) ENA USGS 2008 - 140 Bar MbLg - AB n Atkinson-Boore (2006) ENA USGS 2008 - 200 Bar MbLg - AB

2 Marple, R.T., and P. Talwani, (2000), “Evidence for a buried fault system in the Coastal Plain of the Carolinas and Virginia; Implications for neotectonics in the southeastern United States”, Geological Society of America Bulletin, v. 112, no. 2, pp. 200-220.

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The MCE for the 2500-year return period was determined in general accordance with ACSE 7-10 Sections 21.2.1, 21.2.1.1, and 21.2.2 for a 5% damped response spectra. The site specific design curve and parameters were created based on the procedures outlined in ASCE 7-10 Sections 21.4 and 21.5 and are included in following paragraphs.

The results of the site specific response analysis indicate that the seismic design values can be reduced to approximately 85 to 90 percent of the mapped design curve for a Site Class C.

The site specific design values are provided in the table below. The site specific design curve is included with this report. Based on our analysis, the Seismic Design Category (SDC) for the parking garage can be modified from a “C” to a “B”.

Seismic Design Parameter Value SDS 0.30 g SD1 0.13 g

PGA 0.16 g

To 0.04 sec Ts 0.37 sec

SDC B

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5.0 RECOMMENDATIONS FOR DESIGN AND CONSTRUCTION

5.1 Geotechnical Considerations

The boring data indicates that the native soil conditions encountered at the tested locations are generally compatible with the proposed construction. However, the following geotechnical considerations were identified during the course of this investigation that should be addressed during final design and construction:

n Undocumented fill n Foundation considerations

Undocumented Fill: The majority of borings encountered undocumented fill to depths ranging up to 5-½ feet. The fill material is likely associated with past construction activities. Given the developed nature of the site, existing fill is likely to occur elsewhere within the footprint of the proposed parking garage. Based on the anticipated cut/fill requirements for this project, some of the existing fill will likely be removed during the course of general site grading activities (especially along the berm). The deeper fill areas will remain.

While there is no direct correlation between N-values and relative compaction, the recorded N-values from the soil borings indicate that portions of the existing fill may have received some compactive effort in its placement. Without construction documentation, there is an inherent risk for the owner that compressible fill or unsuitable material within or buried by the fill is present. The risk of unforeseen conditions cannot be eliminated without completely removing the existing fill material. Presuming that the owner can tolerate some risk, the first floor slabs can be supported on the existing fill, although subgrade repair will be necessary to provide a stable subgrade for fill placement and compaction.

To help manage the Owner’s risk of allowing the fill to remain in-place for the slabs, Terracon recommends the existing fill be further evaluated. This should include performing hand auger borings with Dynamic Cone Penetrometer (DCP) tests to check the composition of the existing fill and field density testing to check its consistency and proofrolling of the existing subgrades.

Depending on the findings, test pit excavation may also be necessary. It should be expected that undercutting and replacement of unsuitable fill soils may be required in some areas of the site to improve the subgrade support characteristics.

The existing fill soils (minus organics and other deleterious materials) is expected to be generally satisfactory for re-use as a structural fill. Dependent on the depth of excavation and the prevalent weather conditions at the time of construction, some moisture conditioning (i.e.

wetting or drying) may be necessary to facilitate placement and compaction of this material to structural fill levels.

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Although not directly encountered during the course of our field investigation, the potential exists to encounter remnants of past construction (i.e. the baseball diamond and associated facilities). As such, the construction budget should include a contingency to deal with these occurrences if and where they are encountered as well as any existing underground utilities and their backfill.

Foundation Considerations: Based on the results of the field testing and our engineering analysis, we estimate the total settlements associated with the anticipated structural loads on the order of 1 to 1-½ inches for the parking garage using an allowable bearing pressure of 3,500 psf. To realize the noted allowable bearing pressure, it will be necessary to replace some of the bearing soils to depths of up to 6 to 8 feet below existing grade to remove soft, settlement-prone materials. Based on the boring data, we estimate about 40 to 50 percent of the foundations may be affected.

Alternatively, the ground can be improved by the installation of stone columns to greatly limit the need for foundation subgrade repair. Stone columns have an added benefit as they can also increase the allowable bearing pressure of the foundation soils above what is typically available. Based on past experience with similar structures in the Columbia area, foundations supported on stone columns are typically designed with allowable bearing pressures ranging from 5,000 to 7,000 psf.

Geotechnical engineering recommendations for foundation systems and other earth-related phases of the project are outlined below. The recommendations contains in this report are based upon the results of field and laboratory testing presented in Appendices A and B, engineering analyses, and our current understanding of the proposed project.

5.2 Earthwork

The following presents recommendations for site preparation, excavation, subgrade preparation and placement of engineered fills on the project. The recommendations presented for design and construction of earth supported elements including foundations, retaining walls, and concrete slabs are contingent upon following the recommendation outlined in the following paragraphs. All grading for the structure should incorporate the limits of the proposed structure footprint plus a minimum distance of five feet beyond the construction limits.

Earthwork on the project should be observed and evaluated by Terracon personnel. The evaluation of earthwork should include observation and testing of engineered fill, subgrade preparation, foundations, and other geotechnical conditions exposed during the construction of the project.

5.2.1 Site Preparation

After the removal of the existing pavements, stone, topsoil, and/or remnants of previous construction and any other unsuitable materials should be stripped and removed from the

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Clean topsoil (if any) may be stockpiled for reuse in landscaped areas. Once the contractor’s stripping activities nears completion, we recommend that our representative observe the subgrade to identify any remaining pockets of organics or unsuitable material that should be removed.

Special precautions should be made to remove all existing underground utilities and their associated backfill as the new structure’s foundations or concrete slabs/pavements may overlay these materials. Care should be given to locating and addressing these items during the site preparation phase of the project. If overlooked, they could be detrimental to the long-term performance of the building’s concrete slab/pavement.

5.2.2 Subgrade Preparation

We recommend the exposed subgrades in at-grade areas, cut areas after overburden removal and in areas to be filled should be proofrolled to check for unstable soil conditions upon completion of stripping activities. Proofrolling is a very useful tool in identifying shallow areas of instability in the subgrade. Proofrolling should be performed after a suitable period of dry weather to avoid degrading an otherwise acceptable subgrade. Proofrolling will also aid in evaluating the undocumented existing fill identified within the footprint of the parking garage.

The proofrolling load should be applied with a heavily loaded tandem-axle dump truck, scraper, or with similar approved construction equipment under the observation of the Terracon geotechnical engineer. Any areas that deflect or rut excessively and cannot be stabilized by further rolling should be undercut as recommended by the geotechnical engineer. If conditions are found to be unstable, the subgrade should be undercut to either allow the deeper soils to be reconditioned (densified in place) or to a depth that will provide a firm base for the compaction of the structural fill. The undercut soils should be replaced with compacted structural fill, placed as described in Section 5.2.4.

Positive drainage should be maintained at all times to prevent ponding of stormwater and direct surface runoff away from areas of active construction. This will prevent the weakening of prepared subgrade soils.

5.2.3 Material Types

Engineered fill should meet the following material property requirements:

Fill Type USCS Classification Acceptable Location for Placement On-Site Borrow SC, SM, and CL All locations and elevations

Off-Site Borrow SC and SM All locations and elevations Controlled, compacted 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. A sample of each material type should be submitted to the geotechnical engineer for evaluation. Soils that classify as SC and SM should be utilized for ramp construction.

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5.2.4 Compaction Requirements

ITEM DESCRIPTION

Fill Lift Thickness

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

4 inches in loose thickness when hand-guided equipment (i.e. jumping jack or plate compactor) is used.

Compaction Requirements 1,2

95 percent of the material’s standard Proctor maximum dry unit weight (ASTM D 698) and 98% within 12 inches of subgrade elevations for slabs and/or foundations.

Moisture Content

Within the range of -3 percent and +3 percent of the optimum moisture content as determined by the standard Proctor test at the time of placement and compaction.

1. We recommend that engineered fill be tested for moisture content and compaction during placement. Should the results of the in-place density tests indicate the specified moisture or compaction limits have not been met, the area represented by the test should be reworked and retested as required until the specified moisture and compaction requirements are achieved.

5.2.5 Temporary Excavations

It is recommended that all excavations on this site be performed in accordance with OSHA Excavation Regulations. For open cut excavation for utility lines, foundation construction, the elevator pit or as needed to stabilize subgrade soils, we recommend using the following backslopes for temporary cut slopes of 20 feet or less in height:

n Stiff to very stiff cohesive soil; 1H:1V (OSHA Type B Soils) n Very soft to medium stiff cohesive soil; 1.5H:1V (OSHA Type C Soils) n Granular soil; 1.5H:1V (OSHA Type C Soils) n All existing fill; 1.5H:1V (OSHA Type C Soils)

Open cut excavations should not remain exposed to weather conditions for extended periods.

Seepage or low strength conditions may dictate flatter slopes than those provided above.

The general soils conditions across the site indicate that OSHA Type C soils will likely be encountered during excavation of the elevator pit, foundations, and/or deep utilities. The excavations should be performed in accordance with OSHA Excavation Regulations based on the actual material encountered and field conditions at the time of the excavation.

Compliance with OSHA Excavation requirements is the responsibility of the contractor’s onsite “competent person” representative.

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Deep utility installations and/or deep foundation undercuts at a minimum will likely require a large open excavation to maintain stability. The excavation should conform to OSHA standards for side slopes. If site constraints will not allow for a large open exaction (i.e.

proximity to Building 106), the use of a shoring system will likely be necessary.

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 that Terracon is assuming any responsibility for construction site safety or the contractor's activities; such responsibility shall neither be implied nor inferred.

The boring data indicate that the site soils should generally be excavatable using conventional construction equipment. Trenches and other shallow excavations can be performed using medium to large, rubber-tired backhoes. Large trackhoes will be necessary for the deeper excavations, such as for utility lines, generally due to the mass required to be moved.

5.2.6 Construction Considerations

Upon completion of filling and grading, care should be taken to maintain the subgrade moisture content prior to construction of first floor concrete slab(s). Construction traffic over the completed subgrade should be avoided to the extent practical. If the subgrade should become frozen, desiccated, saturated, or disturbed, the affected material should be removed or these materials should be scarified, moisture conditioned, and recompacted prior to floor slab and pavement construction.

The geotechnical engineer should be retained during the construction phase of the project to evaluate the existing fill, observe earthwork and to perform necessary tests and observations during subgrade preparation; proofrolling; placement and compaction of controlled compacted fills; backfilling of excavations into the completed subgrade, and just prior to construction of foundations and the first floor concrete slab/pavement.

5.3 Foundation Systems

5.3.1 Soil Supported Spread Footings

With proper site preparation and foundation repairs (i.e. undercut and replacement of soft foundation soils, when and where necessary), the proposed structure can be supported utilizing shallow spread footings bearing on in situ soils or compacted Controlled Fill. Design recommendations for shallow foundations for the structure proposed for this site are presented in the following paragraphs.

DESCRIPTION Column Wall

Net allowable bearing pressure 1 3,500 psf 3,500 psf

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DESCRIPTION Column Wall

Minimum dimensions 24 inches 18 inches

Minimum foundation bearing elevation 2 244 feet 244 feet

Approximate total settlement 3 <1-½ inches <1-½ inches

Estimated differential settlement 3 <¾ inch <¾ inch

Equivalent unit weight for passive resistance 4 300 pcf

Coefficient of sliding friction 4 0.35

1. The recommended net allowable bearing pressure is the pressure in excess of the minimum surrounding overburden pressure at the footing base elevation. Assumes any unsuitable fill or soft soils, if encountered, will be undercut and replaced with engineered fill.

2. Based on a FFE of 249.8± feet for load bearing foundation elements.

3. The foundation settlement will depend upon the variations within the subsurface soil profile, the structural loading conditions, the embedment depth of the footings, the thickness of compacted fill, and the quality of the earthwork operations.

4. The sides of the excavation for the spread footing foundation must be nearly vertical and the concrete should be placed neat against these vertical faces for the passive earth pressure values to be valid.

We anticipate that the proposed parking garage may include non-load bearing curtain walls.

This lightly loaded elements we expect that non-load bearing walls can be supported using shallow strip footings. Non-load bearing walls should be structurally independent of the primary load bearing elements of the parking garage. Design recommendations for a shallow foundation system are presented in the following table and paragraphs.

Description Value Net allowable bearing pressure 1 2,000 psf

Minimum foundation embedment 24 inches

Minimum width for continuous wall footings 18 inches Approximate total settlement 2 Less than 1 inch Estimated differential settlement 2 Less than ½ inch

Equivalent unit weight for passive resistance 3 300 pcf Coefficient of sliding friction 3 0.35

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1. The recommended net allowable bearing pressure is the pressure in excess of the minimum surrounding overburden pressure at the footing base elevation.

2. The foundation settlement will depend upon the variations within the subsurface soil profile, the structural loading conditions, the embedment depth of the footings, the thickness of compacted fill, and the quality of the earthwork operations.

3. The sides of the excavation for the spread footing foundation must be nearly vertical and the concrete should be placed neat against these vertical faces for the passive earth pressure values to be valid.

The soil mass providing uplift resistance for the foundations should be calculated as the zone contained within planes that extend up and out from the edges of the top of the foundation to the ground surface at an angle of approximately 30 degrees from the vertical. The ultimate uplift capacity should then be taken as the sum of the weight of soil in this zone plus the weight of the concrete foundation. An effective unit weight of 120 pcf for soil and 150 pcf for reinforced concrete could be used for calculations above the groundwater level.

The allowable foundation bearing pressures apply to dead loads plus design live load conditions. The design bearing pressure may be increased by one-third when considering total loads that include wind or seismic conditions. The weight of the foundation concrete below grade may be neglected in dead load computations. Finished grade is the lowest adjacent grade for perimeter footings and floor level for interior footings.

Footings, foundations, and masonry walls should be reinforced as necessary to reduce the potential for distress caused by differential foundation movement. The use of joints at openings or other discontinuities in masonry walls is recommended.

5.3.2 Construction Recommendations

To check that soil bearing conditions compatible with the design values are achieved, we recommend that the footing excavations be observed and tested by a Terracon representative. This evaluation should include performing hand auger borings and dynamic cone penetration testing (DCP) at different locations and random probing of the foundation bearing surface.

If unsuitable bearing soils are encountered in footing excavations, the excavations 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. The footings could also bear on properly compacted backfill extending down to the suitable soils. Overexcavation for compacted backfill placement below footings should extend laterally beyond all edges of the footings at least 8 inches per foot of overexcavation depth below footing base elevation.

Backfill material should be placed in lifts of 9 inches or less in loose thickness and compacted to at least 95 percent of the material's maximum standard effort maximum dry density (ASTM D 698). We anticipate approximately 40 to 50 percent of the load bearing foundation elements will likely require undercut and replacement to remove soft, settlement susceptible soils.

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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.

If the soils at bearing level become excessively dry, disturbed or saturated, or frozen, the affected soil should be removed prior to placing concrete. Place a lean concrete mud-mat over the bearing soils if the excavations must remain open overnight or for an extended period of time. It is recommended that the geotechnical engineer be retained to observe and test the soil foundation bearing materials.

5.3.3 Shallow Foundations (Stone Columns)

The soil conditions at the site can be improved using stone columns (Geo-piers™ or vibro-piers™) to increase the allowable bearing pressure while limiting static settlements to within acceptable tolerances. The use of such soil modification techniques has allowed the use of allowable bearing pressures of 5,000 to 7,000 psf to proportion the footings for support of similar structures in the Columbia area. The actual value will depend on the number of stone columns per footing and the depth of penetration below the footing bottom as well as the required performance criteria. Such systems are proprietary and are typically designed by the specialty contractor in consultation with the structural engineer and the geotechnical consultant. Locally, these typically include Hayward Baker and Geopier Foundation Company.

The stone columns are referred to as vibropiers and geopiers by those respective contractors.

The Geopier® system uses replacement Rammed Aggregate Pier (RAP) elements to reinforce good to poor soils. Geopier installation involves first drilling a large diameter hole, typically between 30 and 48 inches. Depending on design requirements, drill depths typically range up to about 40 feet. Layers of aggregate are then placed into the drilled hole in lifts of about one foot. A beveled tamper rams each layer of aggregate using vertical impact ramming energy. The tamper densifies aggregate vertically and forces aggregate laterally into cavity sidewalls. In general, vibro-piers are similar to geopier in general construction methods. The primary difference is associated with their compaction methods. The vibro-piers are compacted by the horizontal agitation of a vibrating probe rather than vertical compaction.

This process continues as the probe incrementally rises from the bottom of the borehole. The diameters of the columns are somewhat variable, but a typical column would be about 3 feet.

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In both cases, the process is generally performed on a grid pattern with several elements installed at specific locations (i.e. footings). Further, treated footprint is typically undercut and replaced with a zone of uniformly compacted soil or stone.

The installer of either system should provide detailed design calculations sealed by a professional engineer licensed in the State of South Carolina. The design calculations should demonstrate that the stone column-soil improved system is estimated to control long-term total and differential settlements to that required for the various foundations. The specialty contractor should warrant their work as well as the maximum total and differential settlements they predict. We recommend the design parameters be verified by a full-scale modulus test (similar to a pile load test) performed in the field. Terracon should be retained to monitor the modulus test and subsequent production installation.

The actual required depth and number of stone columns will depend on the foundation layout.

It should be stipulated that the stone columns should be spaced to provide the noted allowable bearing pressure (as a minimum, actual bearing capacity may be significantly larger) while limiting the total settlement to within the range of the structural tolerance.

5.3.4 Foundation Considerations

In the event that ground improved with stone columns is selected for this project, we recommend that the owner budget for a comprehensive precondition survey of surroundings structures be made prior to commencement of ground improvement to provide a baseline of existing building conditions. Terracon can provide these services, including installation of the survey monuments, inclinometers, and precondition photo documentation, as needed to document the existing conditions and monitor the construction vibrations. We recommend the AASHTO R8-96 criteria (a customary used criteria governing construction related vibrations) be utilized for this project.

Based on the current site layout, we do not anticipate foundation loads from the new parking garage (either traditional spread footings or foundations supported on stone columns) will adversely impact the foundation system (or underlying soils) of the existing structure (Building 106 – Mental Health and Dermatology). As such, the need to permanently underpin or shore Building 106 is not anticipated at this time although depending on the depth of excavations temporary ground support may be necessary during construction may be necessary. If the building orientation and/or relative location of the parking garage to the existing structure are modified, Terracon should be notified to review and revise our recommendations accordingly.

5.4 Floor Slabs

5.4.1 Design Recommendations

DESCRIPTION VALUE

Interior building floor system Slab-on-grade concrete.

Modulus of Subgrade Reaction 125 pounds per square inch per in (psi/in)

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DESCRIPTION VALUE

Floor slab support Minimum 12 inches of approved on-site or imported soils placed and compacted in accordance with Earthwork section of this report.

Subbase 4-inch compacted layer of free draining, granular material including fine to coarse sand.

Where appropriate, saw-cut control joints should be placed in the slab to help control the location and extent of cracking. Design and construction of the concrete slab should follow the recommendations presented in the American Concrete Institute (ACI) Design Manual (ACI 302.1R, 318-08, and 360R) for the anticipated loading conditions. The floor slab subgrade should be prepared as discussed in Section 5.2.4.

To minimize the effects of differential settlements across the slabs and to reduce the affects of repeated transient loading from vehicle traffic, the interior joints should be dowelled following recommendations by ACI. In general, the concrete slabs should be designed utilizing the requirements as recommended by ACI for the anticipated structural application.

Slab construction can begin after the completion of any fill placement necessary to establish nominal construction grades. We recommend that floor slabs be designed as ”floating” slabs, that is, fully ground supported and structurally independent of any foundation elements. This is to aid in minimizing the possibility of cracking and displacement of the floor slabs because of differential movements between the slab and the foundation. Positive separations and/or isolation joints should be provided between slabs and all foundations, columns or utility lines to allow independent movement. Interior trench backfill placed beneath slabs should be compacted in accordance with recommendations outlined in the Earthwork section of this report.

5.4.2 Construction Considerations

We recommend the area underlying the floor slab be rough graded and then thoroughly proofrolled with a loaded tandem axle dump truck prior to final grading and placement of base rock. Particular attention should be paid to high traffic areas that were rutted and disturbed earlier and to areas where backfilled trenches are located. Areas where unsuitable conditions are located (including any existing undocumented fill) should be repaired by removing and replacing the affected material with properly compacted fill. All floor slab subgrade areas should be moisture conditioned and properly compacted to the recommendations in this report immediately prior to placement of the base rock and concrete.

On most project sites, the site grading is generally accomplished early in the construction phase.

However as construction proceeds, the subgrade may be disturbed due to utility excavations, construction traffic, desiccation, rainfall, etc. As a result, the floor slab subgrade may not be

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5.5 Lateral Earth Pressures

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.