geotechnical engineering report -...

Geotechnical Engineering Report BMW of Columbia

Killian Commons Parkway Columbia, South Carolina

August 7, 2015 Terracon Project No. 73155048

Prepared for: Ayer Design Group, LLC Rock Hill, South Carolina

Prepared by:

Terracon Consultants, Inc. Columbia, South Carolina

T errac on C ons ul tants , Inc . 521 C lem s on R oad C olum bia, South C arol ina 29229

P [ 803] 741 9000 F [ 803] 741 9900 ter rac on. c om

August 7, 2015 Ayer Design Group, LLC 215 Johnston Street Rock Hill, SC 29730 Attn: Mr. Birk Ayer, P.E. Re: Geotechnical Engineering Report BMW of Columbia Columbia, South Carolina Terracon Project No. 73155048 Dear Mr. Ayer: 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. P73150199, dated May 26, 2015 and Supplemental Change Order, signed June 29, 2015. This report presents the findings of the subsurface exploration and provides geotechnical recommendations concerning earthwork and the design and construction of foundations, floor slabs, and pavements 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. Rajshekhar Sarkar Phillip A. Morrison, P.E. Geotechnical Staff Engineer Geotechnical Department Manager SC Registration No. 17275

TABLE OF CONTENTS

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Page EXECUTIVE SUMMARY ..........................................................................................i 1.0 INTRODUCTION .....................................................................................................1 2.0 PROJECT DESCRIPTION ......................................................................................1

2.1 Project Description ...................................................................................... 1 2.2 Site Location and Description ...................................................................... 2

3.0 SUBSURFACE CONDITIONS.................................................................................3 3.1 Geology ...................................................................................................... 3 3.2 Typical Subsurface Profile ........................................................................... 3 3.3 Groundwater Conditions .............................................................................. 4

4.0 RECOMMENDATIONS FOR DESIGN AND CONSTRUCTION ................................4 4.1 Geotechnical Considerations ....................................................................... 4 4.2 Earthwork ................................................................................................... 6

4.2.1 Site Preparation ............................................................................... 6 4.2.2 Subgrade Preparation (Building Area) .............................................. 7 4.2.3 Subgrade Preparation (Paved areas) ............................................... 8 4.2.4 Material Types ................................................................................. 9 4.2.5 Compaction Requirements ............................................................... 9 4.2.6 Excavation ..................................................................................... 10 4.2.7 Groundwater Considerations .......................................................... 10 4.2.8 Grading and Drainage .................................................................... 11 4.2.9 Construction Considerations .......................................................... 11

4.3 Foundation Systems.................................................................................. 12 4.3.1 Design Recommendations ............................................................. 12 4.3.2 Construction Recommendations..................................................... 13

4.4 Site Seismic Coefficient ............................................................................. 14 4.5 Floor Slabs ............................................................................................... 14

4.5.1 Design Recommendations ............................................................. 14 4.5.2 Construction Considerations .......................................................... 15

4.6 Pavements................................................................................................ 15 4.6.1 Design Recommendations ............................................................. 15 4.6.1 General Design Recommendations ................................................ 16 4.6.2 Construction Considerations .......................................................... 17

5.0 GENERAL COMMENTS .......................................................................................18 APPENDIX A – FIELD EXPLORATION

Exhibit A-1 – Site Location Map Exhibit A-2 – Site Exploration Plan Exhibit A-3 – Boring Location Plan Exhibit A-4 – Field Testing Description Exhibit A-5 – Shear Wave Velocity Profile Exhibits A-6 to A-19 – Boring Logs Exhibits A-20 to A-27 – Test Pit Logs Exhibit A-28 – Photograph Logs

APPENDIX B – LABORATORY TESTING

Exhibit B-1 – Laboratory Testing Description Exhibit B-2 – Laboratory Data Sheet

TABLE OF CONTENTS

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APPENDIX C – SUPPORTING DOCUMENTS Exhibit C-1 – General Notes

Exhibit C-2 – Unified Soil Classification System

Geotechnical Engineering Report BMW of Columbia ■ Columbia, South Carolina August 7, 2015 ■ Terracon Project No. 73155048

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EXECUTIVE SUMMARY

A geotechnical investigation has been performed for the proposed BMW automotive dealership to be constructed on Killian Commons Parkway in Columbia, South Carolina. Thirteen borings, designated B-1 through B-13, and eight test pits, designated TP-1 through TP-8, were advanced to depths of approximately 10 to 20 feet and 7-½ to 14 feet below the existing ground surface, respectively. Based on the information obtained from our subsurface exploration, the site can be developed for the proposed project. The following geotechnical considerations were identified:

The borings and test pits encountered undocumented existing fill to depths of 3 to 17 feet below the existing ground surface throughout the site. The boring samples of the fill materials ranged from silty/clayey sand to clayey silt and sandy clay mixed with organics and some construction debris. Some samples appear to be topsoil. The excavated soils from the test pits contained deleterious, organic materials including stumps and large roots. The N-values in the fill indicate variable consistency, ranging from very loose to medium dense/medium stiff. Given the debris and aggregate noted in the samples, the N-values may be inflated. Below the existing fill, the native soils generally consist of medium dense to dense clayey sands/silty sands and stiff to hard silts/clays.

Groundwater was encountered by the borings at depths ranging from of 6 to 12 feet when checked after 24 hours. No groundwater was observed in the test pits to the 14 foot maximum excavation depth. As such, the noted water readings from the borings may have been perched water above the hard clay soils at depth.

The undocumented existing fill identified throughout the site is not considered suitable to support the proposed structure. The conditions and options for mitigation along with the associated risks were discussed with the design team on July 28, 2015. Per our discussion, we understand that full removal of the existing fill and replacement with new structural fill or stone columns to support the structure and floor slab are the preferred alternatives. For the parking areas and drives, we understand that supporting the pavement by the existing fill is preferred. It should be expected that repairs to the subgrade will be necessary to provide more uniform support for the pavements. This should be considered in the project budget and schedule.

Based on the 2012 International Building Code, the seismic site class for this site is C.

Close monitoring of the construction operations discussed herein will be critical in achieving the design subgrade support. We therefore recommend that the Terracon be retained to monitor this portion of the work.

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 BMW OF COLUMBIA

COLUMBIA, SOUTH CAROLINA

Terracon Project No. 73155048 August 7, 2015

1.0 INTRODUCTION

This report presents the results of our geotechnical engineering services performed for the BMW auto dealership building to be located at Killian Commons Parkway in Columbia, South Carolina. The purpose of these services is to provide information and geotechnical engineering recommendations relative to:

subsurface soil conditions groundwater conditions earthwork foundation design and construction seismic considerations floor slab design and construction pavement design and construction

Our geotechnical engineering scope of work for this project included the advancement of 13 test borings to depths ranging from approximately 10 to 20 feet below existing site grades and geophysical testing to develop the shear wave velocity profile. To further evaluate the existing fill found at the site, a follow-up exploration that included eight test pits to depths of 7-½ to 14 feet has also been performed.

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. Photographs of the test pits are also included in Appendix A. The results of the laboratory testing performed on 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 layout1 Refer to the Boring Location Plan (Exhibit A-3 in Appendix A).

Structure1 The BMW auto dealership will be 18,000 square foot, single-story structure.



ITEM DESCRIPTION

Building construction Steel framing with a concrete slab-on-grade. The exterior is presumed to be a mix of glass and metal siding.

Finished floor elevation1 The finished floor elevation (FFE) is 295.25 feet.

Maximum loads

Based on our conversation with the structural engineer, Mr. Mark Dunlap of Dunlap Engineering, Inc., we understand the following:

Maximum column loads: 60 kips Maximum wall loads: 5.5 klf

We assume the typical floor load would be about 200 psf. Site Grading1 Cut/fill depths for the site are expected to reach depths of up to 5 feet.

Cut and fill slopes1 2H:1V (Horizontal to Vertical) or flatter.

Pavements1 The entrance drive extends into the site from Killian Commons Parkway. The building is encircled by a loop road and perpendicular parking spaces.

Utilities1 Storm drain lines are present on essentially 3 sides of the building. They have inverts depths of 5 to 15 feet.

1. Based on Sheet 1 of 1 provided by Ayers Design Group.

2.2 Site Location and Description

ITEM DESCRIPTION

Location

The site is located at the south end of Killian Commons Parkway, Columbia, South Carolina. A projection of this roadway borders the east side of the property. The site is further bound by I-77 to the west, a car dealership to the north and undeveloped land to the south.

Existing improvements

The site appears to be cleared and somewhat pre-graded but otherwise undeveloped. Based on a review of available aerial photography, the site was wooded and undeveloped until 2006. At that time, the site and the parcels to its north were cleared. The site has remained open but undeveloped since that time. No photographic data is available for the site between 2006 and 2010. In that window, the car dealership to the north of the property was built.

Current ground cover Sparse grass and underbrush.

Existing topography

Based on the provided plan of the site development, the topography slopes downward from northwest to the south and southeast. The surface grades range from Elevation 305 feet at the northwest corner to about 275 feet at the southeast corner. A steep sided draw in the topography is present from south side of the proposed building area to the south side of the property. The base elevation is also about 275 feet.



3.0 SUBSURFACE CONDITIONS

3.1 Geology

Fall Line The site is located in the upper Coastal Plain physiographic province of South Carolina, very near the Fall Line (the transition from the Coastal Plain to the Piedmont province). 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 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.

The underlying Piedmont physiographic province consists of soils generated by the in -place chemical and mechanical weathering of the parent sedimentary and metamorphic rock. A common soil profile includes a surficial clayey or silty layer transitioning to coarser material at depth. Generally dividing the soil layer from the bedrock is a very dense layer referred to as “partially weathered rock”. Partially weathered rock is composed of irregular zones of very dense soil and rock. Partially weathered rock exhibits standard penetration test values of 100 blows per foot (bpf) or more.

The topography of the underlying bedrock surface and the thickness of the various soil and weathered rock strata vary greatly in short, horizontal distances because of variation in mineralogy of the material, previous and present groundwater conditions, and past tectonic activity (faulting, folding, intrusions, etc.). Further, the presence of boulders and rock pinnacles is possible within the soil matrix.

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 and test pit location are indicated on the individual boring/test pit 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, t he transition between materials may be gradual. Based on the results of the borings /test pits, subsurface conditions on the project site can be generalized as follows:



Description Approximate Depth to

Bottom of Stratum (feet) Material Encountered Consistency/Density

Stratum 1 2 to 3 inches Topsoil N/A

Stratum 21 3 to 17 Fill – Silty/clayey sand with organics

Very loose to medium dense

Stratum 3A 152 Clayey sand/sandy clay Loose to medium

dense/stiff

Stratum 3B 123 Clayey silt/sandy clay Medium stiff to very stiff

Stratum 4 204 Silt/sandy clay/clayey silt Stiff to hard

Notes: 1. Test Pits TP-2 was terminated in the existing fill at a depth of 14 feet, the limit of the excavator

reach. Based on the test pit data, this material contains heavy organics such as large roots and stumps as well as some construction debris. The deeper portion of the layer appeared to be topsoil. Photographs providing examples of the observed conditions are included in Appendix A.

2. Not present in Borings B-3, B-4, B-8, B-9, and B-10. 3. Encountered in Borings B-2A, B-3, B-4, B-8 and B-12. 4. Most of the borings terminated in this layer.

3.3 Groundwater Conditions

Groundwater was encountered in the borings at depths of approximately 11-½ to 14 feet below the existing ground surface at the time of field exploration. When checked after 24 hours, groundwater had stabilized 6-½ to 11 feet. Groundwater was not observed in the test pits excavated to depths of 7-½ to 14 feet deep about 2 weeks later. As such, the groundwater conditions may be a perched water condition in the existing fill above the dense coastal plain soils and underlying hard residuum. 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 conditions can change with varying seasonal and weather conditions, and other factors.

4.0 RECOMMENDATIONS FOR DESIGN AND CONSTRUCTION

4.1 Geotechnical Considerations

The boring data indicates that the site may be developed as planned; however, several conditions were identified by the borings that should be considered in the scheme of development. These include the presence of undocumented existing fill throughout the site and variable groundwater depth, as discussed in the following paragraphs.

The primary geotechnical issue identified by the field exploration is presence of a significant layer of undocumented existing fill throughout the majority of the site. The depth of existing fill ranged from 8 feet to 17 feet at the tested locations. The deepest fill was noted in Boring



B-10 near the stormwater management basin. In the planned building area, the existing fill thickness was about 7 to 8 feet. Similar depth existing fill was encountered in the areas around the proposed building a along the entrance drive. The base of the existing fill was not reached at 15 feet in the future development area. The N-values in the fill were variable, ranging from very loose to medium dense. Large organics such as roots and stumps as well as construction debris (crushed aggregate, asphalt and brick fragments). Therefore, the N-values may be inflated somewhat. Based on the provided grading plan, some of the existing fill will be removed from the northwest corner of the site (including the northwest building corner) but the majority of the existing fill will remain.

While there is no direct correlation between N-values and relative compaction, the boring data indicates that the fill received variable, but generally low, compaction in its placement. Further, it contains large organics. As such, there is an inherent risk associated with constructing structures and/or pavements over areas containing existing fill. These include the elevated potential for detrimental post-construction settlement that could result in distress in the structures/pavements. Even with recommended construction testing services, there is a risk for the owner that compressible fill or unsuitable material within or buried by the fill will not be discovered.

If the owner’s risk tolerance is low, the existing fill should be completely removed and replaced with new structural fill. Alternative methods of dealing with the existing fill vary depending on the amount of information developed about the fill and the owner’s risk tolerance. For a structure such as planned for this site and conditions consistent with the boring/test pit data, this may include partial undercutting and replacement of the existing fill to a uniform elevation as well as ground improvement techniques such as stone columns. Combinations of these approaches could also be considered.

The same general logic can be applied to the preparation of the paved areas. To remove the risk of existing fill related issues would require the removal and replacement of the material. If some risk can be tolerated such as the potential development of shallow depressions in the pavement surface (birdbaths), an alternate approach would be to evaluate the existing fill proofrolling to identify weak or unstable areas, undercut them as needed and backfill the areas with well compacted structural fill, possibly using a geo-synthetic material (fabrics or grids) to help stabilize the conditions exposed by excavation.

The potential methods for addressing the existing fill were discussed in a meeting on July 28, 2015 among our engineer, Mr. Ayer and the other design members. We understand that two general approaches are favored for the building area. These include total removal and replacement of the existing fill and the use of stone columns to support the building structure and its floor slab. Both methods allow for the use of conventional shallow spread footings to be used to support the structure as well as a generally standard floor slab, though stone columns may require a somewhat thicker slab-on-grade to essentially span from element to element. In the paved areas, the consensus was to evaluate the existing fill and repair it as



needed to provide a stable subgrade for support of the pavement system. As such, we have directed this report toward these methods of preparing the site/supporting the structure in subsequent paragraphs.

Current plans indicate moderately deep storm drain lines are planned. Depths to groundwater though potentially transitory were present above the utility inverts, primarily in the area south and west of the building. As such, we anticipate that groundwater encountered in this area is generally above the planned invert. These conditions should be considered when setting the final utility inverts and planning the construction activities. In the following sections of this report, we have provided geotechnical engineering recommendations for the noted foundation systems as well as floor slabs, and pavements. The recommendations contained in this report are based upon the results of data presented herein, engineering analyses, and our current understanding of the proposed project.

4.2 Earthwork

The following sections present 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, slabs and pavements are contingent upon following the recommendations outlined in this section.

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

4.2.1 Site Preparation In the proposed development area indicated on the proposed site plan, the topsoil and any other unsuitable or organic materials should be stripped and removed. Topsoil thickness ranged from 2 to 3 inches at the boring/test pit locations. Stripping depths between our boring/test pit locations and across the site could vary considerably. As such, we recommend the actual stripping depths be evaluated by a representative of Terracon during construction to aid in preventing removal of excess material. The stripping should extend at least 10 feet beyond the construction limits. Stripped materials consisting of vegetation and organic materials should be wasted off site, or used to vegetate landscaped areas or exposed slopes after completion of grading operations. After stripping the organic materials, the exposed subgrade should be observed by a Terracon representative and any large concentrations of organics or root mat identified should be removed.

Special precautions should be made to remove all underground utilities and their associated backfill as the new building’s foundations or 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 or pavements.

4.2.2 Subgrade Preparation (Building Area) As discussed in the Section 4.1 - Geotechnical Considerations, two general methods of addressing the undocumented existing fill were favored by the design team for the building area. These included the removal and replacement of the existing fill and the use of stone columns to improve and supplement the support conditions of the existing fill. Each is discussed below.

Removal and Replacement: Though some will be removed to reach the proposed building subgrade, the existing fill depth is generally expected to be on the order of 8 feet. We recommend that the undercutting extend at least 5 feet beyond the outside the exterior edge of the footings. The sidewalls of the undercut area should be sloped to maintain their stability. There is a probability that some of the excavated fill can be reused to backfill the area. As some of the collected samples contained organics and the deeper portions of the fill were wet, the extent of the usable fill is not known. We recommend that our personnel observe the undercut operations and aid in the segregation of the fill during excavation.

The purpose of undercutting activities is to remove the existing fill. As the existing fill’s presence may have caused some degradation of the native soils, some subgrade repairs may be necessary to allow the new fill soils to be compacted on the exposed subgrade to the desired level. Subgrade repairs may include compaction of the exposed subgrade or selective undercutting and replacement. The necessity of the subgrade repairs should be determined by the geotechnical engineer or his representative at the time of excavation .

There is a high probability that wet to saturated subgrade conditions will be exposed by the undercutting. Groundwater was observed in the boring though not in the test pits during the field exploration. Presuming only wet soil conditions are exposed, the fill placement can commence using free draining, fine to coarse sand. A minimum of 18 inches of these materials should be placed. These materials can be compacted in moderately wet conditions. For marginal subgrade areas, the exposed surface should be covered with a medium gauge geo-grid. For this application, we recommend the use of a material such as Tensar TX140 due to its high modulus value. Other materials can be considered, however they should be equivalent to the Tensar material. The material should extend at least 5 feet beyond the area being stabilized.

If groundwater is encountered in the undercut excavation, temporary dewatering can likely be accomplished by sloping the exposed subgrade to the perimeter and removing the water with submersible pumps. To limit the amount of dewatering and to maintain the stability of subgrades, we recommend that the final 3 feet of the undercutting be performed in a rapid manner. Adequate clean sand fill, as noted above, should be stockpiled on site and to



rapidly replace these materials on the grid. The undercutting operations should be monitored by a qualified geotechnical engineer or his representative to check that the subgrades are undercut as recommended. The undercut depth may vary, depending upon the actual site conditions at the time of construction. Some dewatering may be needed and should be considered in the project budget.

Stone Columns: For the application at this site, the stone columns are installed in a grid pattern. They are spaced more widely under the floor slab and more closely together in the foundation area to provide more support of the concentrated and sustained loads. The systems are designed and constructed by proprietary design-build contractors. Locally, these typically include Hayward Baker and Geopier Foundation Company. The stone columns are referred to as vibropiers and geopiers by the respective contractors.

The geopier support elements are typically constructed by drilling a hole, removing a volume of soil, and then building a bottom bulb of clean, open-graded stone while vertically pre-stressing and pre-straining subsoils underlying the bottom bulb. The geopier shaft is built on top of the bottom bulb, using open-graded base course stone placed in thin lifts. Vibropiers are constructed in a similar manner except the hole is formed with a large vibrator which forces the soil aside as it is extended into the ground thereby densifying the surrounding soils. Pre-drilling for stone columns can be required in dense soils and/or to speed construction. The stone columns are filled with layers of No. 67 or 57 stone, each compacted by the noted methods in iterations until the hole is filled.

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 vibropier/geopier 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 vibropier/geopier installation.

Spread footings supported on stone columns can be designed for maximum net allowable bearing pressures 6,000 psf or more. However, the loads for this building may not warrant the close clustering to reach that level. For this application, we recommend a target allow bearing pressure of 3,000 psf. (This would be an equally appropriate level for the undercut and replacement of the fill and is therefore considered the allowable bearing pressure in Section 4.3 and is further discussed in that section).

4.2.3 Subgrade Preparation (Paved areas) In the development’s paved areas, the consensus is to support the pavements on the existing fill presuming the exposed subgrade is found to be stable by proofrolling. Proofrolling should be performed with a heavily loaded tandem axle dump truck or with



similar approved construction equipment under the observation of the Terracon geotechnical engineer. If conditions are found to be unstable, the subgrade should be undercut to soils that would provide a firm base for the compaction of the structural fill unless alternate recommendations are provided by the field geotechnical engineer . The undercut soils should be replaced with compacted structural fill, placed as described in the “Earthwork” section of this report. Given the depth and condition of the existing fill found in the borings and test pits, an elevated level of subgrade repairs should be contemplated in the project schedule and budget.

4.2.4 Material Types Engineered fill should meet the following material property requirements:

Fill Type 1 USCS Classification Acceptable Location for Placement

Free draining Structural fill SW, GW Initial 18 inches of the building area undercut backfill.

Imported Structural Fill SM, SC All other locations and elevations

On-Site Soils (less organics and debris)

SM, SC All other locations and elevations

Notes: 1. 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.

4.2.5 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 95 percent of the material’s maximum standard Proctor dry density (ASTM D 698)

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.



4.2.6 Excavation 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 some excavations, such as for the building undercut, generally due to the mass required to be moved.

As a minimum, all temporary excavations should be sloped or braced as required by Occupational Health and Safety Administration (OSHA) regulations to provide stability and safe working conditions. Temporary excavations will probably be required during grading operations. The grading contractor, by his contract, is usually responsible for designing and constructing stable, temporary excavations and should shore, slope or bench the sides of the excavations as required, to maintain stability of both the excavation sides and bottom. All excavations should comply with applicable local, state and federal safety regulations, including the current OSHA Excavation and Trench Safety Standards.

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.

4.2.7 Groundwater Considerations Groundwater was encountered in the test borings at depths of 6-½ to 11 feet in the borings but not in the test pits. Deep excavations may require alternate dewatering measures. The designers should consider the presence of groundwater when selecting their utility inverts.

Based on the boring data and the provided storm drain inverts, groundwater may be encountered above the trench bottom on the south and west sides of the building. Given the modest difference the depth to groundwater and the invert depths, it may be possible to control the groundwater from within the excavation using temporary drainage sumps to pump out the seeping water while the pipe is being installed. Doing so may require the contractor to work in relatively short sections to quickly excavate the trench, place the bedding and install the pipe. To accomplish this, a 12-inch layer of open-graded stone (#57 stone or equal) can be placed at the bottom of the excavated trench to serve as a drainage medium. This would allow the contractor to avoid wet working conditions. These materials would also provide bedding for the pipe and would not be in addition to a general bedding layer. Periodically, the contractor would need to excavate a sump pit within the trench to allow an area for water to collect and the pump to be set. We recommend using open graded stone such as that used below the pipe to encase the pipe and fill the trench to a level above the original static groundwater level. This should be placed and compacted prior to excavating the next segment of the trench. During excavation of the next segment,



groundwater should continue to be pumped from the prior sump location until a new sump pit is installed and functioning.

4.2.8 Grading and Drainage Adequate positive drainage should be provided during construction and maintained throughout the life of the development to prevent an increase in moisture content of the foundation, pavement and fill/backfill materials. Surface water drainage should be controlled to prevent undermining of cut/fill slopes and structures during and after construc tion.

Gutters and downspouts that drain water a minimum of 10 feet beyond the footprint of the proposed structures are recommended. This can be accomplished through the use of splash-blocks, downspout extensions, and flexible pipes that are designed to attach to the end of the downspout. Flexible pipe should only be used if it is day-lighted in such a manner that it gravity-drains collected water or routed to the storm drain system.

Traffic exposure to wet subgrades can destabilize otherwise satisfactory conditions, requiring remedial work to repair them. We note that conditions of the subgrade can vary between the time of exploration and the time of construction; therefore, the actual method of subgrade preparation should be determined at the time of construction.

Upon completion of filling and grading, care should be taken to maintain the subgrade moisture content prior to construction of floor slabs and pavements. 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. If the subgrade should become frozen, desiccated, saturated or disturbed, the affected material should be removed or these materials should be undercut, moisture condit ioned, and recompacted prior to floor slab and pavement construction. These operations should be observed by a Terracon representative.

4.2.9 Construction Considerations Upon completion of filling and grading, care should be taken to maintain the subgrade moisture content prior to construction of floor slabs and pavements. Construction traffic over the completed subgrade should be avoided to the extent practical. The site should also be graded to prevent ponding of surface water on the prepared subgrades or in excavations. 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 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 the building’s floor slabs.



4.3 Foundation Systems

As discussed in the Section 4.1 - Geotechnical Considerations, two general methods of addressing the undocumented existing fill were favored by the design team for the building area. These included the removal and replacement of the existing fill and the use of stone columns to improve and supplement the support conditions of the existing fill. These are discussed in detail in Section 4.2.2. The following foundation recommendations presume that one of the two noted methods is performed. If stone columns are used, they should be spaced to provide the noted allowable bearing pressure while limiting settlement to the indicated level.

4.3.1 Design Recommendations DESCRIPTION COLUMN WALL

Net allowable bearing pressure 1 3,000 psf

Minimum dimensions 24 inches 18 inches Minimum embedment below finished grade for frost protection 2 18 inches

Approximate total settlement <1 inch

Estimated differential settlement <¾ inch <¾ inch over 40 feet

Equivalent unit weight for passive resistance 3 300 pcf

Coefficient of sliding friction 3 0.30 1. Presumes the existing fill in the building area is addressed as discussed in Section 4.2.2. 2. 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.

3. And to reduce the effects of seasonal moisture variations in the subgrade soils. 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. Passive resistance in the upper 1 foot of the soil profile should be neglected. If passive resistance is used to resist lateral loads, the base friction should be neglected.

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.



4.3.2 Construction Recommendations To check that soil bearing conditions compatible with the design value 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 surface.

Based on the condition of the surficial portion of the site soil profile, some subgrade repairs may needed to provide uniform foundation support. 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. The overexcavation should then be backfilled up to the footing base elevation with well-graded granular material placed in lifts of 9 inches or less in loose thickness and compacted to at least 95 per cent of the material's maximum standard effort maximum dry density (ASTM D 698).

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 so il 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.



4.4 Site Seismic Coefficient

Code Used Site Classification

2012 International Building Code (IBC) 1 C 2 1. In general accordance with the 2012 International Building Code which refers to ASCE7. 2. Based upon the subsurface conditions encountered on the project site and the average

shear wave velocity of 1,458 ft/s derived from the geophysical testing performed for the site owner at the site.

4.5 Floor Slabs

As discussed in the Section 4.1 - Geotechnical Considerations, two general methods of addressing the undocumented existing fill were favored by the design team for the building area. These included the removal and replacement of the existing fill and the use of stone columns to improve and supplement the support conditions of the existing fill. These are discussed in detail in Section 4.2.2. The following floor slab recommendations presume that one of the two noted methods is performed. If stone columns are used, additional measures in the slab reinforcement plan may be needed to accommodate the variation in subgrade support.

4.5.1 Design Recommendations DESCRIPTION VALUE

Interior building floor system Slab-on-grade concrete.

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 subbase material.

A subgrade prepared and tested as recommended in this report should provide adequate support for lightly loaded floor slabs. Slab construction can begin after the completion of any necessary undercutting or in-place stabilization. We recommend that floor slabs be designed as ”floating” slabs, that is, fully ground supported and structurally independent of any building footings or walls. 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.

Control joints should be saw cut into the slab after concrete placement in accordance with ACI Design Manual, Section 302.1R-37 8.3.12 (tooled control joints are not recommended). 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. Other design and construction considerations, as outlined in the ACI Design Manual Section 302.1R, are recommended.

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

4.5.2 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 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 suitable for placement of base rock and concrete and corrective action will be required to repair the damaged areas.

4.6 Pavements

4.6.1 Design Recommendations Information relating to traffic loading and frequencies has not been provided to us. Based on our experience with similar projects, we have assumed a 10-year design period and the following traffic volume:

Light-duty: 18,000 ESALS Medium-duty: 60,000 ESALS

Based on our experience with similar soil conditions, we have used a CBR value of 5 for the design. Subgrade preparation in the pavement areas should be performed as outlined in the “Earthwork” section of this report.



Pavement Design Alternatives

Pavement Type

Material Layer Thickness (inches)

Light-Duty Medium-Duty

Flexible

HMA Surface Course 1 2 2

Tack Coat 0.04 to 0.08 gal/sy 0.04 to 0.08 gal/sy

HMA Intermediate Course 1 - 2

Prime Coat (If required) 0.30 gal/sy 0.30 gal/sy

Base Course1 6 6

Rigid Portland Cement Concrete 1 5 6

Base Course1 4 4

1. See “General Design Recommendations” section below.

The above sections represent minimum thicknesses and, as such, periodic maintenance should be anticipated. Pavements subjected to high traffic volumes and heavy trucks require thicker pavement sections.

For areas subject to concentrated and repetitive loading conditions such as entrances, dumpster pads and areas where heavy-truck frequently stop or turn, we recommend using a Portland cement concrete pavement with a thickness of at least 7 inches underlain by at least 4 inches of crushed stone. For dumpster pads, as a minimum, the concrete pavement area should be large enough to support the container and tipping axle of the refuse truck.

4.6.1 General Design Recommendations Aggregate base course should be SCDOT Macadam Base Course (SCDOT Section 305). Asphaltic cement concrete should be an approved mix design selected from the current SCDOT Standard Type C (SCDOT Section 402 and 403). Compaction levels of the asphalt and Macadam Base Course materials should conform to SCDOT requirements.

Portland cement concrete should conform to Section 501 of the SCDOT Standard Specifications and have a minimum flexural strength of 550 psi and compressive strength of 4,000 psi. Portland cement concrete pavement should contain about 5 to 7 percent entrained air and should have a maximum water to cement ratio of about 0.45. A maximum slump of 4 inches should be used for non-slip formed placement, and 2 inches for slip formed placement. The compressive and flexural strength of the pavement should be tested to verify its strength. The concrete should be deposited by truck mixers or agitators and placed a maximum of 90 minutes from time the water is added to the mix.

To limit the amount of random slab cracking due to drying, shrinkage, or thermal expansion and contraction of the concrete, we recommend a 15-foot maximum joint spacing. They



should be laid out as square as possible. In the dumpster pad areas, we further recommend that the pavement sections be reinforced with 6-inch by 12-inch, D5 x D3 deformed welded wire fabric. Note that the heavier steel should be in the longitudinal direction. The reinforcing wire fabric should be placed just slightly above the mid-depth of the slab.

Transitions from dissimilar paving materials should be thickened and then tapered to the design section within about 5 feet. Isolation joints should be used at penetrations within the paving and at the termination of the paving to allow free relative movement. Polyurethane, self-leveling, elastomeric joint sealant should be used to seal all joints within the concrete pavement to limit the flow of water to the underlying subgrade.

Construction joints should be designed as butt joints. They should be reinforced with A615 Grade 40 smooth steel dowels for load transfer while holding adjacent panels in plane and allowing for longitudinal expansion and contraction. The dowels should be placed at the mid -height of the slab and placed perpendicular to the panel edge, both vertically and horizontally. One end should be lightly greased or sleeved to break the concrete bond and allow free inter-panel movement.

4.6.2 Construction Considerations Pavement subgrades prepared early in the project should be carefully evaluated as the time for pavement construction approaches. We recommend the pavement areas be rough graded and then thoroughly proofrolled with a loaded tandem-axle dump truck. Particular attention should be paid to high traffic areas that were rutted and disturbed and to areas where backfilled trenches are located. Areas where unsuitable conditions are located should be repaired by replacing the materials with properly compacted fill. Future pavement maintenance may be necessary due to post construction settlements within the old fills.

Future performance of pavements constructed on the site will be dependent upon maintaining stable moisture content of the subgrade soils; and, providing for a planned program of preventative maintenance. The performance of all pavements can be enhanced by minimizing excess moisture that can reach the subgrade soils. The following recommendations should be considered at minimum:

Site grading at a minimum 2 percent grade away from the pavements; Sealing all landscaped areas in, or adjacent to pavements to reduce moisture

migration to subgrade soils; Placing compacted backfill against the exterior side of curb and gutter; and, Placing curb, gutter and/or sidewalk directly on subgrade soils without the use of

base course materials. Preventative maintenance should be planned and provided through an on-going pavement management program in order to enhance future pavement performance. Preventative



maintenance activities are intended to slow the rate of pavement deterioration, and to preserve the pavement investment.

Preventative maintenance consists of both localized maintenance (e.g. crack and joint sealing and patching) and global maintenance (e.g. surface sealing). Preventative maintenance is usually the first priority when implementing a planned pavement maintenance program and provides the highest return on investment for pavements. Prior t o implementing any maintenance, additional engineering observation is recommended to determine the type and extent of preventative maintenance.

5.0 GENERAL COMMENTS

Terracon should be retained to review the final design plans and specifications so comments can be made regarding interpretation and implementation of our geotechnical recommendations in the design and specifications. Terracon also should be retained to provide testing and observation during excavation, grading, foundation and construction phases of the project.

The analysis and recommendations presented in this report are based upon the data obtained from the borings performed at the indicated locations and from other information discussed in this report. This report does not reflect variations that may occur between borings, across the site, or due to the modifying effects of weather. The nature and extent of such variations may not become evident until during or after construction. If variations appear, we should be immediately notified so that further evaluation and supplemental recommendations can be provided.

The scope of services for this project 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.

This report has been prepared for the exclusive use of our client for specific application to the project discussed and has been prepared in accordance with generally accepted geotechnical engineering practices. No warranties, either express or implied, are intended or made. Site safety, excavation support, and dewatering requirements are the responsibility of others. In the event that changes in the nature, design, or location of the project as outlined in this report are planned, the conclusions and recommendations contained in this report shall not be considered valid unless Terracon reviews the changes and either verifies or modifies the conclusions of this report in writing.

APPENDIX A FIELD EXPLORATION

SITE LOCATION

BMW of Columbia Killian Commons Parkway Columbia, South Carolina

TOPOGRAPHIC MAP IMAGE COURTESY OF THE U.S. GEOLOGICAL SURVEY QUADRANGLES INCLUDE: BLYTHEWOOD, SC (1/1/1990) and FORT JACKSON NORTH, SC (1/1/1990).

521 Clemson Road Columbia, SC 29229

73155048 Project Manager: Drawn by: Checked by: Approved by:

PTK

RS

PAM

1”=24,000 SF A-1 & A-2

August 2015

Project No. Scale: File Name: Date: A-1

Exhibit RS

EXPLORATION PLAN

BMW of Columbia Killian Commons Parkway Columbia, South Carolina

521 Clemson Road Columbia, SC 29229

DIAGRAM IS FOR GENERAL LOCATION ONLY, AND IS NOT INTENDED FOR CONSTRUCTION PURPOSES

73155048

AERIAL PHOTOGRAPHY PROVIDED BY MICROSOFT BING MAPS

PTK

RS

PAM

AS SHOWN A-1 & A-2

August 2015

Scale:

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Responsive ■ Resourceful ■ Reliable Exhibit A-4

Field Exploration Description

Thirteen test borings were drilled at the site on June 15, 2015. The borings were drilled to depths ranging from approximately 10 to 20 feet below the existing ground surface. In our follow-up exploration on June 30, 2015, eight test pits were excavated to depths of up to 14 feet below the existing ground surface.

The approximate locations of the borings and test pits are shown on the attached Exploration Plan (Exhibit A-2) and Boring Location Plan (Exhibit A-3). The test pits and borings were located in the field by using the proposed site plan and an aerial photograph of the site, and measuring from existing property lines. The test pits and boring locations shown on the Boring Location Plan are approximate and should be considered accurate only to the degree implied by the method of location.

The test borings were advanced with an ATV mounted CME-550X drill rig utilizing 3-¼ inch inside diameter hollow-stem augers. A CME automatic SPT hammer was used to advance the split-barrel sampler in the borings performed on this site. A greater efficiency is typically achieved with the automatic hammer compared to the conventional safety hammer operated with a cathead and rope. Published correlations between the SPT values and soil properties are based on the lower efficiency cathead and rope method. This higher efficiency affects the standard penetration resistance blow count (N) value by increasing the penetration per hammer blow over what would be obtained using the cathead and rope method. The effect of the automatic hammer's efficiency has been considered in the interpretation and analysis of the subsurface information for this report.

Representative disturbed soil samples were obtained from the borings and were placed in sealed containers and returned to our laboratory where our engineer visually reviewed and classified them. The purposes of this review were to check the drillers’ field classifications and visually estimate the soils’ relative constituents (sand, clay, etc.). The soil types and penetrometer values are shown on the Boring Logs. These records represent our interpretation of the field conditions based on the driller’s field logs and our engineer’s review of the soil samples. The lines designating the interfaces between various strata represent approximate boundaries only, as transitions between materials may be gradual.

At the conclusion of the drilling activities, the borings were checked for the presence of groundwater. The holes were kept open overnight for the groundwater to stabilize and were checked after 24 hours. After which, the borings were backfilled with the auger cuttings.

Our exploration services include storing the collected soil samples and making them available for inspection for 60 days from the report date. The samples will then be d iscarded unless requested otherwise.



The test pits were advanced with a rubber tired backhoe to penetrate through the existing fill into native soils. Excavation was observed by a Terracon engineer to see the composition of the fill. At the conclusion of the field testing, the test pits were backfilled with the excavated soils. The soils were packed using the excavator bucket and tires. While the soils were replaced in a firm condition, no particular density was achieved. Excess materials were wasted at the site. Repair of the test pits in this manner was the contractual limit of our work.

Some settlement of backfill soils in the test pit areas is likely. This may result in a surface depression. Terracon assumes that the backfill in the test pit areas are temporary which will be repaired by the contractor during actual construction. We have marked the locations of the test pits on the plans so that they can reexcavated and then backfilled in thin lifts during construction, but recommend that they be surveyed to more accurately locate them.

Field Seismic Testing

Terracon utilized the SeisOpt® ReMi™ method to develop the full depth shear wave velocity profile at the site for use in determining the seismic site class. This method employs non -linear optimization technology to derive one-dimensional S-wave velocities from refraction microtremor (ambient noise) recordings using a typical seismograph and standard, low frequency, refraction geophones. We utilized 12 receivers (geophones) set along a straight-line array with a 15±-foot receiver spacing for a total length of about 345 feet along Array 1 shown on the attached Boring Location Plan (Exhibit A-3). Unfiltered, 30-second records were recorded using the background ‘noise’ created by the moving traffic and other ambient vibrations. The collected data, the response spectrum in the 5 to 40 Hz range, was processed using the computer software SeisOpt® ReMi™ by Optim, LLC with the results plotted as a conventional shear wave velocity vs. depth profile. The shear wave velocity profile obtained using the SeisOpt® ReMi™ data reduction method is shown on Exhibit A-5.

521 CLEMSON ROAD COLUMBIA, SC 29229

PH. (803) 741-9000 FAX. (803) 741-9900

A-5

ExhibitSHEAR WAVE VELOCITY PROFILE

BMW of ColumbiaKillian Commons ParkwayColumbia, South Carolina

Project Mngr.

Drawn By:

Checked By:

Approved By:

RS

PTK

RS

PAMDate:

Project No.

Scale:

File Name:

73155048As Shown

August 2015

A-5

-100

-75

-50

-25

00 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

Dep

th, f

tShear-Wave Velocity, ft/s

Vs100' = 1458 ft/s


PHOTOGRAPH LOGS

Geotechnical Engineering Report BMW of Columbia■ Columbia, South Carolina , 2015 ■ Terracon Project No. 73155048


Roots at TP-1 encountered at 6 feet Stumps at TP-2 encountered at 5 feet

Stumps at TP-2 encountered at 10 feet Brick fragments at TP-3 encountered at 7

Stumps at TP-4 encountered at 6 feet Roots and stumps at TP- 5

Geotechnical Engineering Report BMW of Columbia■ Columbia, South Carolina , 2015 ■ Terracon Project No. 73155048


Aggregate and bricks fragments at TP-6 Roots and stumps at TP-7

Wood, asphalt and bricks fragments at TP-8 Roots and stumps at TP-8

APPENDIX B LABORATORY TESTING

Geotechnical Engineering Report BMW of Columbia ■ Columbia, SC August 7, 2015 ■ Terracon Project No. 73155048

Responsive ■ Resourceful ■ Reliable Exhibit B-1

Laboratory Testing Description

Samples retrieved during the field exploration were taken to the laboratory for further observation by the project geotechnical engineer and were classified in accordance with the Unified Soil Classification System (USCS) described in Appendix C. At that time, the field descriptions were confirmed or modified as necessary and an applicable laboratory testing program was formulated to determine engineering properties of the subsurface materials.

Laboratory tests were conducted on selected soil samples and the test results are presented in this appendix. The laboratory test results were used for the geotechnical engineering analyses, and the development of earthwork recommendations. Laboratory tests were performed in general accordance with the applicable ASTM, local or other accepted standards.

Selected soils obtained from the site were tested for the following engineering properties:

Compaction Characteristics of Soil using Standard Effort ASTM D698-12

APPENDIX C SUPPORTING DOCUMENTS

Exhibit C-2

UNIFIED SOIL CLASSIFICATION SYSTEM

Criteria for Assigning Group Symbols and Group Names Using Laboratory Tests A Soil Classification

Group Symbol Group Name B

Coarse Grained Soils: More than 50% retained on No. 200 sieve

Gravels: More than 50% of coarse fraction retained on No. 4 sieve

Clean Gravels: Less than 5% fines C

Cu 4 and 1 Cc 3 E GW Well-graded gravel F Cu 4 and/or 1 Cc 3 E GP Poorly graded gravel F

Gravels with Fines: More than 12% fines C

Fines classify as ML or MH GM Silty gravel F,G,H Fines classify as CL or CH GC Clayey gravel F,G,H

Sands: 50% or more of coarse fraction passes No. 4 sieve

Clean Sands: Less than 5% fines D

Cu 6 and 1 Cc 3 E SW Well-graded sand I Cu 6 and/or 1 Cc 3 E SP Poorly graded sand I

Sands with Fines: More than 12% fines D

Fines classify as ML or MH SM Silty sand G,H,I Fines classify as CL or CH SC Clayey sand G,H,I

Fine-Grained Soils: 50% or more passes the No. 200 sieve

Silts and Clays: Liquid limit less than 50

Inorganic: PI 7 and plots on or above “A” line J CL Lean clay K,L,M PI 4 or plots below “A” line J ML Silt K,L,M

Organic: Liquid limit - oven dried

0.75 OL Organic clay K,L,M,N

Liquid limit - not dried Organic silt K,L,M,O

Silts and Clays: Liquid limit 50 or more

Inorganic: PI plots on or above “A” line CH Fat clay K,L,M PI plots below “A” line MH Elastic Silt K,L,M

Organic: Liquid limit - oven dried

0.75 OH Organic clay K,L,M,P

Liquid limit - not dried Organic silt K,L,M,Q Highly organic soils: Primarily organic matter, dark in color, and organic odor PT Peat

A Based on the material passing the 3-inch (75-mm) sieve B If field sample contained cobbles or boulders, or both, add “with cobbles

or boulders, or both” to group name. C Gravels with 5 to 12% fines require dual symbols: GW-GM well-graded

gravel with silt, GW-GC well-graded gravel with clay, GP-GM poorly graded gravel with silt, GP-GC poorly graded gravel with clay.

D Sands with 5 to 12% fines require dual symbols: SW-SM well-graded sand with silt, SW-SC well-graded sand with clay, SP-SM poorly graded sand with silt, SP-SC poorly graded sand with clay

E Cu = D60/D10 Cc = 6010

2

30

DxD

)(D

F If soil contains 15% sand, add “with sand” to group name. G If fines classify as CL-ML, use dual symbol GC-GM, or SC-SM.

H If fines are organic, add “with organic fines” to group name. I If soil contains 15% gravel, add “with gravel” to group name. J If Atterberg limits plot in shaded area, soil is a CL-ML, silty clay. K If soil contains 15 to 29% plus No. 200, add “with sand” or “with gravel,”

whichever is predominant. L If soil contains 30% plus No. 200 predominantly sand, add “sandy” to

group name. M If soil contains 30% plus No. 200, predominantly gravel, add

“gravelly” to group name. N PI 4 and plots on or above “A” line. O PI 4 or plots below “A” line. P PI plots on or above “A” line. Q PI plots below “A” line.

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