geotechnical engineering report -...

Geotechnical Engineering ReportCaswell County Public Library

Yanceyville, North CarolinaJune 15, 2017

Project No. 75175054 Revised

Prepared for:Gunn Memorial Public Library

Yanceyville, North Carolina

Prepared by:Terracon Consultants, Inc.

Greensboro, North Carolina

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TABLE OF CONTENTS

PAGEEXECUTIVE SUMMARY ............................................................................................................ i1.0 INTRODUCTION ..............................................................................................................12.0 PROJECT INFORMATION ..............................................................................................1

2.1 Project Description .................................................................................................12.2 Site Location and Description ................................................................................1

3.0 SUBSURFACE CONDITIONS .........................................................................................23.1 Site Geology...........................................................................................................23.2 Typical Profile ........................................................................................................23.3 Groundwater ..........................................................................................................3

4.0 RECOMMENDATIONS FOR DESIGN AND CONSTRUCTION .......................................34.1 Geotechnical Considerations .................................................................................34.2 Earthwork ..............................................................................................................4

4.2.1 Site Preparation .........................................................................................44.2.2 Material Types ...........................................................................................54.2.3 Compaction Requirements .........................................................................54.2.4 Utility Trench Backfill ..................................................................................64.2.5 Grading and Drainage ................................................................................64.2.6 Earthwork Construction Considerations .....................................................6

4.3 Foundation Recommendations ..............................................................................74.3.1 Foundation Design Recommendations.......................................................7

4.4 Seismic Considerations .........................................................................................84.5 Floor Slabs ............................................................................................................8

4.5.1 Design Recommendations ..........................................................................84.5.2 Floor Slab Construction Considerations .....................................................8

4.6 Pavements .............................................................................................................94.6.1 Subgrade Preparation .................................................................................94.6.2 Design Considerations .............................................................................104.6.3 Estimates of Minimum Pavement Thickness ..............................................114.6.4 Pavement Drainage .................................................................................124.6.5 Pavement Maintenance ...........................................................................12

5.0 GENERAL COMMENTS ................................................................................................12

APPENDIX A – FIELD EXPLORATIONExhibit A-1 Site Location PlanExhibit A-2 Boring Location PlanExhibit A-3 Field Exploration / Laboratory DescriptionExhibits A-4 to A-11 Boring Logs

APPENDIX B – LABORATORY TESTINGExhibit B-1 Atterberg Limits

APPENDIX C – SUPPORTING DOCUMENTSExhibit C-1 General NotesExhibit C-2 Unified Soil Classification

Geotechnical Engineering Report - RevisedCaswell County Public Library ■ Yanceyville, North CarolinaJune 15, 2017 ■ Terracon Project No. 75175054

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EXECUTIVE SUMMARY

Terracon has completed the geotechnical engineering report for the Caswell County PublicLibrary project to be located in Yanceyville, North Carolina. Seven (7) soil test borings wereperformed in the area of the proposed building and pavement areas.

Based on the information obtained from our subsurface exploration, the following geotechnicalconsiderations were identified:

n Existing fill soils were encountered in borings B-3, B-3-A, and B-7 to depths ranging from1.5 to 3 feet below the existing surface. The fill consists of medium stiff fat clay and loosesilty sand. The majority of the fill appears to be placed in an uncontrolled manner. Isolatedareas of more compressible material may be present at other locations and may requireremoval and replacement. Based on the encountered subsurface conditions throughout thesite, we do not believe the refusal material in borings B-3 to be bedrock. The refusal in B-3is likely debris or a utility. We recommend performing test pits, before construction or at thestart of construction, in the vicinity of borings B-3 to determine the cause of the refusal.

n Based on our site visit and information pertaining to the site, settlement related distress wasnot observed in the existing building in the area of the proposed development. There is aninherent risk of structure settlement from compressible fill or unsuitable material within orburied by the fill that may not be discovered. This risk of unforeseen conditions cannot beeliminated without completely removing the existing fill within the building pad, parking anddriveway areas. These risks can be reduced by performing adequate testing and evaluationduring construction. This evaluation should begin with proofrolling areas at grade or to befilled upon.

n Care should be taken during any excavation adjacent the existing building to not underminefoundations for the existing building. If excavation is required in the area of existingfootings, recommendations for underpinning can be provided if needed.

n Groundwater and difficult excavations are not anticipated to impact grading operations.

n Most of the near surface soils are fat clays (plastic soils). After grading, some plastic soilsmay be encountered at proposed bearing elevations for buildings, at floor slab subgradeelevations and at roadway subgrades. Treatment of foundation and slabs bearing in theclayey material is discussed herein.

n A net allowable bearing pressure of up to 2,000 pounds per square foot can be used forbuilding foundation design.


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n We anticipate that unstable plastic soils may be present at or near planned pavementsubgrade elevations. We recommend earthwork be performed during the summer topossibly reduce the instability of these subgrade plastic soils. Considering such, werecommend that contingencies be placed in the project budget for additional ABC stone(6 to 12 inches) and geogrid (BX-1100) for at least 50 percent of the pavement areas. Atthe time of constructions, the determination can be made as to what areas, if any, willrequire stabilization.

n The geotechnical engineer should be retained during the construction phase of theproject to observe earthwork and to perform necessary tests and observations duringsubgrade preparation; proofrolling; placement and compaction of controlled compactedfills; backfilling of excavations into the completed subgrade, and just prior to constructionof foundations.

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

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GEOTECHNICAL ENGINEERING REPORTCASWELL COUNTY PUBLIC LIBRARY

YANCEYVILLE, NORTH CAROLINATerracon Project No. 75175054

June 15, 2017

1.0 INTRODUCTION

Terracon has completed the geotechnical engineering report for the proposed Caswell CountyPublic Library project to be located in Yanceyville, North Carolina. Seven (7) soil test boringswere performed across the site.

The purpose of these services is to provide information and geotechnical engineeringrecommendations relative to:

n subsurface soil conditions n foundation design and constructionn groundwater conditionsn site preparation / earthwork

n pavementsn floor slab design and construction

2.0 PROJECT INFORMATION

2.1 Project DescriptionITEM DESCRIPTION

Proposed construction

The proposed project consists of renovation of existing libraryfacility and new construction of a single-story library addition,approximately 7,582 square feet in area and constructed usingsteel framing composed of metal studs and brick veneer with aslab-on-grade floor. We anticipate that column, wall, and floorloads will be less than 150 kips per column, 3 kips per linearfoot and 300 pounds per square foot, respectively.

Finished floor elevation (assumed) Unknown.Grading We anticipate maximum cut and fill depths of less than 3 feet.

2.2 Site Location and DescriptionITEM DESCRIPTIONLocation 161 Main Street East, Yanceyville, North Carolina.

Existing improvements Existing single-story building with asphalt driveway and parkinglots.

Current ground cover Asphalt pavement and grass.

Existing topography Based on google maps aerial the site appears to be relativelyflat.



If any of the project information outlined above is inconsistent with the proposed construction, orif the design changes, Terracon requests the opportunity to review our recommendations.

3.0 SUBSURFACE CONDITIONS

3.1 Site Geology

Piedmont Geology:The project site is located in the Piedmont Physiographic Province, an area underlain by ancientigneous and metamorphic rocks. The residual soils in this area are the product of in-placechemical weathering of rock. The typical residual soil profile consists of clayey soils near thesurface where soil weathering is more advanced, underlain by sandy silts / silty sands thatgenerally become harder / denser with depth to the top of parent bedrock. In residual materials thetransition from soil to rock occurs gradually over a vertical distance ranging from a few feet totens of feet. This transitional zone is termed “partially weathered rock” which is defined forengineering purposes as residual material that can be drilled with soil drilling methods andexhibits standard penetration test values in excess of 100 blows per foot. According to the 1985Geologic Map of North Carolina, the bedrock under the site is Granitic Rock from thePermian/Pennsylvanian period.

3.2 Typical ProfileBased on the results of the borings, subsurface conditions on the project site can be generalizedas follows:

Approximately 6 to 8 inches of asphalt pavement was encountered in borings B-1 through B-6.Underlying the asphalt pavement, approximately 4 to 7 inches of aggregate base course (ABCstone) was encountered. Approximately up to 4 to 5 inches of topsoil was encountered inborings B-5 and B-6. Beneath the surficial material, existing fill and residual material wasencountered in each boring.

Existing fill soils were encountered in borings B-3, B-3-A, and B-7 to depths ranging from 1.5 to 3feet below the existing surface. The fill consists of medium stiff fat clay and loose silty sand. Themajority of the fill appears to be placed in an uncontrolled manner. Isolated areas of morecompressible material may be present at other locations and may require removal andreplacement. In boring B-3, an unknown object or material caused auger refusal.

The residual material at the site generally consists of zones of fat clay (CH), lean clay (CL),elastic silts (MH), sandy silts (ML), clayey sands (SC) and silty sands (SM). Most of the surfaceclays are moderately to highly plastic. The silts and clays were soft to stiff and sands wereloose to very dense.



Partially weathered rock was encountered in borings B-4 and B-5 at depths ranging from 8 to 18feet below existing ground surface. Auger refusal materials, which we interpret to likelyrepresent the top of rock were encountered in borings B-4 and B-5 at depths ranging from 9.7 to19.5 feet below existing ground surface.

For a detailed description of the conditions encountered in the borings, refer to the boring logs inAppendix A of this report. Stratification boundaries on the boring logs represent the approximatelocation of changes in soil types; in-situ, the transition between materials may be gradual.

3.3 GroundwaterThe boreholes were observed for the presence and level of groundwater while drilling and afterthe short period they were allowed to remain open. Groundwater was not observed in theborings at the time of observation.

Groundwater level fluctuations can occur due to seasonal variations in the amount of rainfall,runoff and other factors not evident at the time the borings were performed. Therefore,groundwater levels during construction or at other times in the life of the structure may be higheror lower than the levels indicated on the boring logs.

We do not expect the groundwater level to have a significant effect on the design andconstruction of the project, except possibly near the drainage feature for construction of theretaining wall.

4.0 RECOMMENDATIONS FOR DESIGN AND CONSTRUCTION

4.1 Geotechnical ConsiderationsExisting fill soils were encountered in borings B-3, B-3-A, and B-7 to depths ranging from 1.5 to 3feet below the existing surface. The fill consists of medium stiff fat clay and loose silty sand. Themajority of the fill appears to be placed in an uncontrolled manner. Isolated areas of morecompressible material may be present at other locations and may require removal andreplacement. Based on the encountered subsurface conditions throughout the site, we do notbelieve the refusal material in borings B-3 to be bedrock. The refusal in B-3 is likely debris or autility. We recommend performing test pits, before construction or at the start of construction, inthe vicinity of borings B-3 to determine the cause of the refusal. This risk of unforeseen conditionscannot be eliminated without completely removing the existing fill within the building pad, parkingand driveway areas. These risks can be reduced by performing adequate testing and evaluationduring construction. This evaluation should begin with proofrolling areas at grade or to be filledupon.

Care should be taken during any excavation adjacent the existing building to not underminefoundations for the existing building. If excavation is required in the area of existing footings,recommendations for underpinning can be provided if needed.



Most of the near surface soils are fat clays (plastic soils). After grading, some plastic soils may beencountered at proposed bearing elevations for buildings, at floor slab subgrade elevations and atroadway subgrades. Treatment of foundation and slabs bearing in the clayey material is discussedherein.

We anticipate that unstable plastic soils may be present at or near planned pavement subgradeelevations. We recommend earthwork be performed during the summer to possibly reduce theinstability of these subgrade plastic soils. Considering such, we recommend that contingenciesbe placed in the project budget for additional ABC stone (6 to 12 inches) and geogrid (BX-1100)for at least 50 percent of the pavement areas. At the time of constructions, the determinationcan be made as to what areas, if any, will require stabilization.

The geotechnical engineer should be retained during the construction phase of the project toobserve earthwork and to perform necessary tests and observations during subgradepreparation; proofrolling; placement and compaction of controlled compacted fills; backfilling ofexcavations into the completed subgrade, and just prior to construction of foundations.

4.2 Earthwork

4.2.1 Site PreparationBased on our laboratory testing and soil classification, the current natural moisture content ofthe on-site, near-surface soil is near the soil’s plastic limit. When the moisture content of soilreaches or exceeds its plastic limit, instability of the soil subgrade can be expected, especiallyunder construction traffic. To help minimize soil disturbance and undercut potential, werecommend that positive site drainage be insisted upon during the project. The use of truckedequipment, in lieu of rubber tired vehicles, should also be considered.

Site preparation should begin by removing the existing trees, undergrowth, and existing asphaltfrom the site. After the existing vegetation is removed, the site should be grubbed and the topsoilstripped and stockpiled for use in revegetating landscape areas or disposed of off-site. Based onthe borings, we expect 3 to 4 inches of topsoil and 3 to 3.5 inches of asphalt will requireremoval. Existing aggregate base course material may be left in place, if desired, to helpprotect the site subgrades during the site preparation activities. Actual stripping depths mayvary and should be evaluated by a Terracon representative at the time of construction.

After the materials are removed, the subgrade soils should be evaluated visually for plasticity.High plasticity soils are not desirable at or near subgrades because of their potential to shrinkand swell due to changes in moisture content. These soils may be used as fill in non-structuralareas provided they are not placed within 1.5 feet of pavement subgrade and can be properlycompacted. If existing highly plastic, CH and MH soils are present at building subgradeelevation, these should be undercut at least 12 inches and replaced with low to non-plastic soilmaterial.



After site stripping and plasticity evaluation, we recommend proofrolling in areas to receive fill orat the subgrade elevation to detect soft or loose soils. Proofrolling should be performed with aloaded, tandem-axle dump truck or similar rubber-tired construction equipment with a minimumgross weight of 20 tons. A representative of the geotechnical engineer should observe theproofrolling to identify areas of unstable or unsuitable subgrades. Proofrolling operations should beperformed after a suitable period of dry weather to avoid degrading an otherwise acceptablesubgrade.

4.2.2 Material TypesEngineered fill should meet the following material property requirements:

Fill Type 1 USCS Classification Acceptable Location for PlacementImported Low- to

Moderate-Plasticity Soil

CL, ML, SC or SM All locations and elevations.

Sand / Gravel withless than 15% fines

(silt and clay)GW/GP, SW/SP 2

NCDOT CABC (crushed aggregate base course) may beused beneath pavements.2

NCDOT No. 57 (washed, crushed stone) may be used asa capillary break beneath floor slabs.2

On-site soils SM, ML, SC, CL Generally suitable when placed at appropriate moisturecontent.

On-site soils CH, MH Use at depths greater than 3 feet from planned buildingfinished grades.

1. Controlled, compacted fill should consist of approved materials that are free of organic matter anddebris. A sample of each material type should be submitted to the geotechnical engineer for evaluation.

2. “Clean” sand (less than 15% silt and clay) should not be used as general site fill in building and pavementareas to reduce risk of perched water developing in the surface fill as water infiltrating the sand fill becomestrapped above the less permeable clay located near the ground surface.

4.2.3 Compaction RequirementsItem Description

Fill Lift Thickness 9-inches or less in loose thickness (4” to 6” lifts when hand-operated equipment is used)

Compaction Requirements 1 Minimum of 95% of the materials standard Proctor maximumdry density (ASTM D698)

Moisture ContentWithin the range of -3% to +3% of optimum moisture content asdetermined by the standard Proctor test at the time ofplacement and compaction

1. Engineered fill should be tested for moisture content and compaction during placement. If in-placedensity tests indicate the specified moisture or compaction limits have not been met, the arearepresented by the tests should be reworked and retested as required until the specified moisture andcompaction requirements are achieved.



4.2.4 Utility Trench BackfillAll trench excavations should be made with sufficient working space to permit constructionincluding backfill placement and compaction. If utility trenches are backfilled with relatively cleangranular material, they should be capped with at least 18 inches of cohesive fill in non-pavementareas to reduce the infiltration and conveyance of surface water through the trench backfill.

Utility trenches are a common source of water infiltration and migration. All utility trenches thatpenetrate beneath the building should be effectively sealed to restrict water intrusion and flowthrough the trenches that could migrate below the building. We recommend constructing aneffective clay “trench plug” that extends at least 5 feet out from the face of the building exterior.The plug material should consist of clay compacted at a water content at or above the soilsoptimum water content. The clay fill should be placed to completely surround the utility line and becompacted in accordance with recommendations in this report.

Some of the on-site soils encountered in utility trenches will likely include fat clays that willgenerally not be suitable for trench backfill in structural areas. If the fat clays are to be used in non-structural areas, these soils will likely require drying.

4.2.5 Grading and DrainageDuring construction, grades should be sloped to promote runoff away from the constructionarea. Final grades should be sloped away from the structure on all sides to prevent ponding ofwater. If gutters / downspouts do not discharge directly onto pavement, they should notdischarge directly adjacent to the building in landscaped areas. This can be accomplishedthrough the use of splash-blocks, downspout extensions, and flexible pipes that are designed toattach to the end of the downspout if necessary. Flexible pipe should only be used if it is day-lighted in such a manner that it gravity-drains collected water. Splash-blocks should also beconsidered below hose bibs and water spigots. Paved surfaces which adjoin the buildingshould be sealed with caulking or other sealant to prevent moisture infiltration at the buildingenvelope; maintenance should be performed as necessary to maintain the seal.

4.2.6 Earthwork Construction ConsiderationsAlthough the exposed subgrade is anticipated to be relatively stable upon initial exposure, unstablesubgrade conditions could develop during general construction operations, particularly if the soilsare wetted and/or subjected to repetitive construction traffic. The use of light constructionequipment would aid in reducing subgrade disturbance. Should unstable subgrade conditionsdevelop, stabilization measures will need to be employed.

Upon completion of filling and grading, care should be taken to maintain the subgrade moisturecontent prior to construction of floor slabs and pavements. Construction traffic over thecompleted subgrade should be avoided to the extent practical. The site should also be gradedto prevent ponding of surface water on the prepared subgrades or in excavations. If the



subgrade should become frozen, desiccated, saturated, or disturbed, the affected materialshould be removed or these materials should be scarified, moisture conditioned, andrecompacted prior to floor slab and pavement construction.

All temporary excavations should be sloped or braced as required by Occupational Health andSafety Administration (OSHA) regulations to provide stability and safe working conditions.

The geotechnical engineer should be retained during the construction phase of the project toobserve earthwork and to perform necessary tests and observations during subgradepreparation; proof-rolling; placement and compaction of controlled compacted fills; backfilling ofexcavations into the completed subgrade, and just prior to construction of building floor slabs.

4.3 Foundation RecommendationsIn our opinion, the proposed building can be supported by a shallow, spread footing foundationsystem consisting of shallow foundations bearing on residual soil, approved existing fill or newcontrolled fill. Design recommendations for foundation systems are presented in the followingtable and paragraphs.

4.3.1 Foundation Design RecommendationsDescription Value

Net allowable bearing pressure 1 2,000 psfMinimum embedment below lowest adjacent finishedgrade2 18 inches

Approximate total settlement 3 Less than 1 inch

Estimated differential settlement 3 Less than 3/4 inch over 40 feet

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

2. In areas of plastic soil, the footing excavations should be extended to a depth of at least 3 feet below finishedgrades and backfilled with non-plastic material.

3. The actual magnitude of settlement that will occur beneath the foundation slab depends upon the variations withinthe subsurface soil profile, the structural loading conditions and the quality of the foundation excavation. Theestimated total and differential settlements listed assume that the foundation related earthwork and the foundationdesign are completed in accordance with our recommendations.

Due to the plastic surface soils, we recommend the perimeter foundations be extended to a depthof at least 3 feet below finished grades and backfilled with non-plastic material.

A representative of the geotechnical engineer should be retained at the time of foundationconstruction to examine the bearing conditions in the foundation excavations. A combination ofhand auger borings, dynamic cone penetrometer (DCP) testing, and probing should beperformed as appropriate to confirm the suitability of the foundation bearing materials for the



design bearing pressure. Soft, loose, or otherwise unsuitable materials should be over-excavated and replaced with compacted soil fill.

The base of all foundation excavations should be free of water and loose soil prior to placingconcrete. Concrete should be placed soon after excavating to reduce bearing soil disturbance.Should the soils at bearing level become excessively disturbed or saturated, the affected soilshould be removed prior to placing concrete.

4.4 Seismic ConsiderationsCode Used Site Classification

2005 ASCE 7(ref. 2012 IBC)

CSs = 0.195 S1 = 0.076

Fa = 1.2 Fv = 1.7SDS = 0.156 SD1 = 0.086

4.5 Floor Slabs

4.5.1 Design RecommendationsItem Description

Floor slab support Approved/prepared site soils or new engineered fill

Modulus of subgrade reaction (k) 100 pounds per square inch per inch (psi/in) for pointloading conditions.

Stone Base Course 1 At least 4 inches of crushed stone (NCDOT CABC orNo. 57)

1. The floor slab design should include a capillary break, comprised of free-draining, compacted,granular material, at least 4 inches thick and can be considered as part of the low volume changezone. Free-draining granular material should have less than 5 percent fines (material passing the#200 sieve). Other design considerations such as cold temperatures and condensationdevelopment could warrant more extensive design provisions.

For the floor slabs partially bearing on highly plastic soils, we recommend that the soils beundercut at least 12 inches and replaced with low to non-plastic material or stone.

4.5.2 Floor Slab Construction ConsiderationsOn most project sites, the site grading is generally accomplished early in the construction phase.However as construction proceeds, the floor slab subgrade may be disturbed due to utilityexcavations, construction traffic, desiccation, rainfall, etc. As a result, the floor slab subgrade maynot be suitable for placement of base rock and concrete and corrective action will be required.



We recommend the area underlying the floor slab be rough graded and then thoroughlyproofrolled with a loaded tandem axle dump truck prior to final grading and placement of baserock. Particular attention should be paid to high traffic areas that were rutted and disturbed earlierand to areas where backfilled trenches are located. Areas where unsuitable conditions arelocated should be repaired by removing and replacing the affected material with properlycompacted fill. All floor slab subgrade areas should be moisture conditioned and properlycompacted to the recommendations in this report immediately prior to placement of the base rockand concrete.

4.6 Pavements

4.6.1 Subgrade PreparationOn most project sites, the site grading is accomplished relatively early in the construction phase.Fills are placed and compacted in a uniform manner. However, as construction proceeds,excavations are made into these areas, rainfall and surface water saturates some areas, heavytraffic from concrete trucks and other delivery vehicles disturbs the subgrade and many surfaceirregularities are filled in with loose soils to improve trafficability temporarily. As a result, thepavement subgrades, initially prepared early in the project, should be carefully evaluated as thetime for pavement construction approaches.

We recommend the moisture content and density of the top 9 inches of the subgrade beevaluated and the pavement subgrades be proofrolled within two days prior to commencement ofactual paving operations. Areas not in compliance with the required ranges of moisture or densityshould be moisture conditioned and recompacted. Particular attention should be paid to hightraffic areas that were rutted and disturbed earlier and to areas where backfilled trenches arelocated. Areas where unsuitable conditions are located should be repaired by removing andreplacing the materials with properly compacted fills.

As previously stated, some of the near surface soils are highly plastic clays. It is not desirableto have these plastic soils at subgrade for pavements and the presence of these soils atsubgrade would likely affect the pavement service life. When dry, these soils should proofrollsuccessfully; however, over time, these soils may get wet due to infiltration through cracks in thepavement or water migration through the base course.

We recommend that contingencies be placed in the project budget for additional ABC stone (6to 12 inches) and geogrid (BX-1100) for at least 50 percent of the pavement areas. At the timeof constructions, the determination can be made as to what areas, if any, will requirestabilization.



Utilizing geogrid can help extend the pavement service life if used in areas of high plasticity soilsand unstable areas. If a significant precipitation event occurs after the evaluation or if the surfacebecomes disturbed, the subgrade should be reviewed by qualified personnel immediately prior topaving. The subgrade should be in its finished form at the time of the final review.

4.6.2 Design ConsiderationsTraffic patterns and anticipated loading conditions were not available at the time that this reportwas prepared. However, we anticipate that traffic loads will be produced primarily by automobile,light truck traffic and a weekly dumpster truck visit. The thickness of pavements subjected toheavy truck traffic have not been considered.

Expansive soils are present at this site. This report provides recommendations to help mitigatethe effects of soil shrinkage and expansion. However, even if these recommendations arefollowed some pavement distress could still occur. It is, therefore, important to minimize moisturechanges in the subgrade both during construction and during the life of the pavement to reduceshrink/swell movements.

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

n Final grade adjacent to parking lots and drives should slope down from pavement edges ata minimum 2%;

n The subgrade and the pavement surface should have a minimum ¼ inch per foot slope topromote proper surface drainage;

n Install pavement drainage surrounding areas anticipated for frequent wetting (e.g., gardencenters, wash racks);

n Install joint sealant and seal cracks immediately;n Seal all landscaped areas in, or adjacent to pavements to reduce moisture migration to

subgrade soils;n Place compacted, low permeability backfill against the exterior side of curb and gutter; and,n Place curb, gutter and/or sidewalk directly on clay subgrade soils rather than on unbound

granular base course materials.



4.6.3 Estimates of Minimum Pavement Thickness

Pavement Type MaterialLayer Thickness (inches)

Light Duty Heavy Duty

Rigid

Portland Cement Concrete(4,000 psi) 5 7

Crushed Aggregate Base Course(NCDOT CABC Type 1 or Type 2) 4 4

Flexible(Superpave)

Asphalt Surface(NCDOT SF-9.5A) 3* 1.5

Asphalt Binder(NCDOT I-19.0B) or (S9.5B) -- 2.5

Crushed Aggregate Base Course(NCDOT CABC Type 1 or Type 2) 6 8

Note: * - Placed in two, 1.5-inch lifts.

The placement of a partial pavement thickness for use during construction is not suggestedwithout a detailed pavement analysis incorporating construction traffic. In addition, we shouldbe contacted to confirm the traffic assumptions outlined above. If the actual traffic varies fromthe assumptions outlined above, modification of the pavement section thickness will berequired.

Recommendations for pavement construction presented depend upon compliance withrecommended material specifications. To assess compliance, observation and testing shouldbe performed under the direction of the geotechnical engineer.

Asphalt concrete aggregates and base course materials should conform to the North CarolinaDepartment of Transportation (NCDOT) "Standard Specifications for Roads and Structures.”Concrete pavement should be air-entrained and have a minimum compressive strength of 4,000psi after 28 days of laboratory curing per ASTM C-31.

The performance of all pavements can be enhanced by minimizing excess moisture which canreach the subgrade soils. The following recommendations should be considered a minimum:

n site grading at a minimum 2 percent grade away from the pavements;n subgrade and pavement surface with a minimum 1/4 inch per foot slope to

promote proper surface drainage; andn installation of joint sealant to seal cracks immediately.n Seal all landscaped areas in, or adjacent to pavements to reduce moisture

migration to subgrade soils;n Place compacted, low permeability backfill against the exterior side of curb and

gutter; and,



n Place curb, gutter and/or sidewalk directly on low permeability subgrade soilsrather than on unbound granular base course materials.

4.6.4 Pavement DrainagePavements should be sloped to provide rapid drainage of surface water. Water allowed to pondon or adjacent to the pavements could saturate the subgrade and contribute to prematurepavement deterioration. In addition, the pavement subgrade should be graded to provide positivedrainage within the granular base section. Appropriate sub-drainage or connection to a suitabledaylight outlet should be provided to remove water from the granular subbase.

4.6.5 Pavement MaintenanceThe pavement sections provided in this report represent minimum recommended thicknessesand, as such, periodic maintenance should be anticipated. Therefore preventive maintenanceshould be planned and provided for through an on-going pavement management program.Maintenance activities are intended to slow the rate of pavement deterioration, and to preservethe pavement investment. Maintenance consists of both localized maintenance (e.g., crack andjoint sealing and patching) and global maintenance (e.g., surface sealing). Preventivemaintenance is usually the first priority when implementing a pavement maintenance program.Additional engineering observation is recommended to determine the type and extent of a costeffective program. Even with periodic maintenance, some movements and related cracking maystill occur and repairs may be required.

5.0 GENERAL COMMENTS

Terracon should be retained to review the final design plans and specifications so commentscan be made regarding interpretation and implementation of our geotechnical recommendationsin the design and specifications. Terracon also should be retained to provide observation andtesting services during grading, excavation, foundation construction and other earth-relatedconstruction phases of the project.

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

The scope of services for this project does not include either specifically or by implication anyenvironmental or biological (e.g., mold, fungi, bacteria) assessment of the site or identification orprevention of pollutants, hazardous materials or conditions. If the owner is concerned about thepotential 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 theproject discussed and has been prepared in accordance with generally accepted geotechnicalengineering practices. No warranties, either express or implied, are intended or made. Sitesafety, excavation support, and dewatering requirements are the responsibility of others. In theevent that changes in the nature, design, or location of the project as outlined in this report areplanned, the conclusions and recommendations contained in this report shall not be consideredvalid unless Terracon reviews the changes and either verifies or modifies the conclusions of thisreport in writing.

APPENDIX A

FIELD EXPLORATION

TOPOGRAPHIC MAP IMAGE COURTESY OFTHE U.S. GEOLOGICAL SURVEY

QUADRANGLES INCLUDE: YANCEYVILLE, NC(1/1/2002).

SITE LOCATION

Caswell County Public Library161 Main Street East

Yanceyville, NC7327 W Friendly Ave Ste GGreensboro, NC 27410-6253

75175054

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

PURPOSES

Project Manager:

Drawn by:

Checked by:

Approved by:

L. Akins

L. Akins

J. Hoskins

L. Akins

5/23/2017

Project No.

File Name:

Date:

A-1

Exhibit

SITE

1”=2,000’Scale:

EXPLORATION PLAN

7327 W Friendly Ave Ste GGreensboro, NC 27410-6253

75175054AERIAL PHOTOGRAPHY PROVIDED BYMICROSOFT BING MAPS

Caswell County Public Library161 Main Street East

Yanceyville, NCDIAGRAM IS FOR GENERAL LOCATION ONLY,AND IS NOT INTENDED FOR CONSTRUCTION

PURPOSES

Project Manager:

Drawn by:

Checked by:

Approved by:

L. Akins

L. Akins

J. Hoskins

L. Akins

5/23/2017

Scale:

Project No.

File Name:

Date:

N.T.S.

A-2

Exhibit


Responsive ■ Resourceful ■ Reliable Exhibit A-3

Field Exploration

The boring locations were established in the field by measuring from existing site features andestimating right angles. The locations of the borings should be considered accurate only to thedegree implied by the means and methods used to define them.

The borings were drilled by Mobile-57 truck-mounted drill rig equipped with hollow stem augers.Samples of the soil encountered in the borings were obtained using the split barrel samplingprocedures.

In the split-barrel sampling procedure, the number of blows required to advance a standard2-inch O.D. split-barrel sampler the last 12 inches of the typical total 18-inch penetration bymeans of a 140-pound safety hammer with a free fall of 30 inches, is the standard penetrationresistance value (SPT-N). This value is used to estimate the in-situ relative density ofcohesionless soils and consistency of cohesive soils. Soil samples were taken at 2.5-footintervals above a depth of 10 feet and at 5-foot intervals below 10 feet.

The samples were tagged for identification, sealed to reduce moisture loss, and taken to ourlaboratory for further examination, testing, and classification. Information provided on the boringlogs attached to this report includes soil descriptions, consistency evaluations, boring depths,sampling intervals, and groundwater conditions. The borings were backfilled with auger cuttingsprior to the drill crew leaving the site.

A field log of each boring was prepared by the drill crew. These logs included visualclassifications of the materials encountered during drilling as well as the driller’s interpretation ofthe subsurface conditions between samples. Final boring logs included with this reportrepresent the engineer's interpretation of the field logs and include modifications based onlaboratory observation of the samples.

Descriptive classifications of the soils indicated on the boring logs are in accordance with theenclosed General Notes and the Unified Soil Classification System. Also shown are estimatedUnified Soil Classification Symbols. A brief description of this classification system is attachedto this report.

3-2-2N=4

5-5-6N=11

4-7-10N=17

50/5"

13-40-50/3"50/3"

0.5

3.0

8.0

13.0

14.8

TOPSOIL, 6" Topsoil

RESIDUAL - FAT CLAY (CH), with sand, tan brown, soft, wet

SILTY SAND (SM), trace mica, tan brown, medium dense, moist

PARTIALLY WEATHERED ROCK - SILTY SAND (SM), with quartz fragments, tanwhite, moist

PARTIALLY WEATHERED ROCK - SILTY SAND (SM), tan brown, moist

Boring Terminated at 14.8 Feet

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Hammer Type: AutomaticStratification lines are approximate. In-situ, the transition may be gradual.

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161 Main Street East Yanceyville, NCSITE:

Page 1 of 1

Advancement Method:Hollow Stem Auger

Abandonment Method:

Notes:

Project No.: 75175054

Drill Rig: Mobile B-57

Boring Started: 5/22/2017

BORING LOG NO. B-1Gunn Memorial Public LibraryCLIENT:161 Main Street East

Driller: M. Hartley

Boring Completed: 5/22/2017

Exhibit:

Rhonda Griffin

A-4

See Exhibit A-3 for description of fieldprocedures.See Appendix B for description of laboratoryprocedures and additional data (if any).

See Appendix C for explanation of symbols andabbreviations.

PROJECT: Caswell County Public Library

7327 W Friendly Ave Ste GGreensboro, NC

At completion of drilling: dryWATER LEVEL OBSERVATIONS

At completion of drilling: dry

DEPTH

LOCATION

Latitude: 36.404163° Longitude: -79.332919°

See Exhibit A-2

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1-1-2N=3

5-12-27N=39

29-50/1"50/1"

20-21-21N=42

12-48-50/2"50/2"

0.6

3.0

6.0

8.0

13.0

14.7

TOPSOIL, 7" Topsoil

RESIDUAL - FAT CLAY (CH), with sand, tan brown, soft, wet

SILTY SAND (SM), with quartz fragments, tan brown, medium dense, moist


SILTY SAND (SM), tan, dense, moist


Boring Terminated at 14.7 Feet

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Page 1 of 1


Abandonment Method:

Notes:





Driller: M. Hartley


Exhibit:

Rhonda Griffin

A-5







DEPTH

LOCATION


See Exhibit A-2

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3-50/3"50/3"

0.30.7

1.8

ASPHALT, 3" AsphaltAGGREGATE BASE COURSE, 5" ABC StoneFILL - SILTY SAND (SM), trace clay and concrete fragments, dark gray, wet to moist

Auger Refusal at 1.8 Feet

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Page 1 of 1


Abandonment Method:

Notes:





Driller: M. Hartley


Exhibit:

Rhonda Griffin

A-6







DEPTH

LOCATION


See Exhibit A-2

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LL-PL-PI

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3-6-3N=9

2-2-4N=6

6-14-14N=28

4-8-12N=20

11-11-21N=32

0.30.7

3.0

6.0

8.0

13.0

15.0

ASPHALT, 3" AsphaltAGGREGATE BASE COURSE, 5" ABC StoneFILL - SILTY SAND (SM), with clay, brown, loose, moist

RESIDUAL - FAT CLAY (CH), trace sand, tan, medium stiff, moist

SILTY SAND (SM), witth quartz fragments, tan white, medium dense, moist

SANDY SILT (ML), tan brown, very stiff, moist

SILTY SAND (SM), tan, dense, moist

Boring Terminated at 15 Feet

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Page 1 of 1


Abandonment Method:

Notes:




BORING LOG NO. B-3-AGunn Memorial Public LibraryCLIENT:161 Main Street East

Driller: M. Hartley


Exhibit:

Rhonda Griffin

A-7







DEPTH

LOCATION


See Exhibit A-2

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4-2-5N=7

2-4-7N=11

7-15-16N=31

14-50/5"50/5"

50/0"

0.3

1.0

3.0

6.0

8.0

9.7

ASPHALT, 3.5" AsphaltAGGREGATE BASE COURSE, 9" ABC Stone

RESIDUAL - CLAYEY SAND (SC), orange brown, loose, wet

FAT CLAY (CH), with sand, tan orange, stiff, moist

SILTY SAND (SM), with quartz fragments, tan, dense, moist

PARTIALLY WEATHERED ROCK - SILTY SAND (SM), with quartz fragments, tan,moist


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Page 1 of 1


Abandonment Method:

Notes:





Driller: M. Hartley


Exhibit:

Rhonda Griffin

A-8







DEPTH

LOCATION


See Exhibit A-2

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ATTERBERGLIMITS

LL-PL-PI

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1-2-1N=3

13-15-21N=36

5-9-9N=18

7-11-17N=28

34-35-50N=85

0.4

3.0

6.0

TOPSOIL, 5" TopsoilRESIDUAL - SANDY FAT CLAY (CH), tan orange, soft, wet

SILTY SAND (SM), tan brown, dense, moist

SILTY SAND (SM), with quartz fragments, tan brown, medium dense to very dense,wet to moist

26 59-20-39

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Page 1 of 2


Abandonment Method:

Notes:





Driller: M. Hartley


Exhibit:

Rhonda Griffin

A-9







DEPTH

LOCATION


See Exhibit A-2

WA

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ATTERBERGLIMITS

LL-PL-PI

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10-50/1"50/1"

18.0

19.5

SILTY SAND (SM), with quartz fragments, tan brown, medium dense to very dense,wet to moist (continued)

PARTIALLY WEATHERED ROCK - SILTY SAND (SM), with rock fragments and mica,tan brown, moist


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Page 2 of 2


Abandonment Method:

Notes:





Driller: M. Hartley


Exhibit:

Rhonda Griffin

A-9







DEPTH

LOCATION


See Exhibit A-2

WA

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ON

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ATTERBERGLIMITS

LL-PL-PI

WA

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1-2-4N=6

2-3-5N=8

4-6-8N=14

3-4-6N=10

0.3

3.0

6.0

10.0

TOPSOIL, 3" TopsoilRESIDUAL - LEAN CLAY (CL), with sand, tan orange, medium stiff, wet

SANDY SILT (ML), trace clay, orange brown, medium stiff, wet

SILTY SAND (SM), tan orange, medium dense, moist


26 47-21-26

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Page 1 of 1


Abandonment Method:

Notes:





Driller: M. Hartley


Exhibit:

Rhonda Griffin

A-10







DEPTH

LOCATION


See Exhibit A-2

WA

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RC

ON

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(%

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ATTERBERGLIMITS

LL-PL-PI

WA

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1-2-3N=5

0-2-4N=6

4-5-7N=12

3-5-5N=10

0.3

3.0

6.0

10.0

TOPSOIL, 3" TopsoilFILL - FAT CLAY (CH), with sand, tan orange, medium stiff, wet

RESIDUAL - CLAYEY SAND (SC), orange brown, loose to medium dense, wet tomoist

ELASTIC SILT (MH), trace sand, red orange, stiff, moist


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Page 1 of 1


Abandonment Method:

Notes:





Driller: M. Hartley


Exhibit:

Rhonda Griffin

A-11







DEPTH

LOCATION


See Exhibit A-2

WA

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ON

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(%

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ATTERBERGLIMITS

LL-PL-PI

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APPENDIX BLABORATORY TESTING

0

10

20

30

40

50

60

0 20 40 60 80 100

CH o

r

OH

CL o

r

OL

ML or OL

MH or OH

PL PIBoring ID Depth Description

SANDY FAT CLAY

LEAN CLAY with SAND

CH

CL

Fines

PLASTICITY

INDEX

LIQUID LIMIT

"U" L

ine

"A" L

ine

59

47

20

21

39

26

63

71

LL USCS

B-5

B-6

ATTERBERG LIMITS RESULTSASTM D4318

1 - 2.5

1 - 2.5

PROJECT NUMBER: 75175054PROJECT: Caswell County Public Library

SITE: 161 Main Street East Yanceyville, NC

CLIENT: Gunn Memorial Public Library 161 Main Street East

EXHIBIT: B-17327 W Friendly Ave Ste G

Greensboro, NC

LAB

OR

AT

OR

Y T

ES

TS

AR

E N

OT

VA

LID

IF S

EP

AR

AT

ED

FR

OM

OR

IGIN

AL

RE

PO

RT

.

AT

TE

RB

ER

G L

IMIT

S 7

5175

054

CA

SW

ELL

CO

UN

TY

PU

.GP

J T

ER

RA

CO

N_D

AT

AT

EM

PLA

TE

.GD

T

6/2/

17

CL-ML

APPENDIX CSUPPORTING DOCUMENTS

Exhibit C-2

UNIFIED SOIL CLASSIFICATION SYSTEM

Criteria for Assigning Group Symbols and Group Names Using Laboratory Tests ASoil Classification

GroupSymbol Group Name B

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

Gravels:More than 50% ofcoarse fraction retainedon 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 coarsefraction passes No. 4sieve

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 theNo. 200 sieve

Silts and Clays:Liquid limit less than 50

Inorganic:PI J CL Lean clay K,L,M

PI J ML Silt K,L,M

Organic:Liquid limit - oven dried

0.75 OLOrganic clay K,L,M,N

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

Silts and Clays:Liquid limit 50 or more

Inorganic:CH Fat clay K,L,M

MH Elastic Silt K,L,M

Organic:Liquid limit - oven dried

0.75 OHOrganic 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) sieveB If field sample

C Gravels with 5 to 12% fines require dual symbols: GW-GM well-gradedgravel with silt, GW-GC well-graded gravel with clay, GP-GM poorlygraded gravel with silt, GP-GC poorly graded gravel with clay.

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

E Cu = D60/D10 Cc =6010

230

DxD

)(D

F If soil containsG If fines classify as CL-ML, use dual symbol GC-GM, or SC-SM.

H

I If soil containsJ If Atterberg limits plot in shaded area, soil is a CL-ML, silty clay.K

whichever is predominant.L If soil contains

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

N PIO PIP PI plots on or aboveQ

geotechnical engineering report -...

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