Report of Subsurface Exploration and Geotechnical Engineering Evaluation

Transcription

1 Report of Subsurface Exploration and Geotechnical Engineering Evaluation Proposed Chatham County Jail Pittsboro, North Carolina F&R Project No. 66N-0097 Prepared For: CHATHAM COUNTY P.O. Box 1809 Pittsboro, NC Prepared By: Froehling & Robertson, Inc. 310 Hubert Street Raleigh, North Carolina November 16, 2011 Corporate HQ: 3015 Dumbarton Road Richmond, Virginia T F VIRGINIA NORTH CAROLINA SOUTH CAROLINA MARYLAND DISTRICT OF COLUMBIA A Woman-Owned Business

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3 TABLE OF CONTENTS SECTION PAGE EXECUTIVE SUMMARY PURPOSE & SCOPE OF SERVICES PROJECT INFORMATION SITE LOCATION AMD DESCRIPTION PROPOSED CONSTRUCTION EXPLORATION PROCEDURES SUBSURFACE EXPLORATION LABORATORY TESTING REGIONAL GEOLOGY & SUBSURFACE CONDITIONS REGIONAL GEOLOGY SUBSURFACE CONDITIONS GENERAL SURFICIAL MATERIALS RESIDUAL SOILS PARTIALLY WEATHERED ROCK & AUGER REFUSAL SOIL MOISTURE AND GROUNDWATER CONDITIONS GEOTECHNICAL DESIGN RECOMMENDATIONS GENERAL DEVELOPMENT CONSIDERATIONS FOUNDATION DESIGN SLAB-ON-GRADE FLOORS RETAINING WALLS PAVEMENT DESIGN CUT AND FILL SLOPES GEOTECHNICAL CONSTRUCTION RECOMMENDATIONS SITE PREPARATION STRUCTURAL FILL PLACEMENT AND COMPACTION PWR EXCAVATION FOUNDATION CONSTRUCTION RECOMMENDATIONS TEMPORARY EXCAVATION RECOMMENDATIONS CONTINUATION OF SERVICES LIMITATIONS ii

4 APPENDIX I Boring Location Plan Subsurface Profiles APPENDICES APPENDIX II Key to Soil Classification Unified Soil Classification Chart Boring Logs APPENDIX III Laboratory Testing APPENDIX IV ASFE Document Important Information about Your Geotechnical Engineering Report iii

5 EXECUTIVE SUMMARY This Executive Summary is provided as a brief overview of our geotechnical engineering evaluation for the project and is not intended to replace more detailed information contained elsewhere in this report. As an overview, this summary inherently omits details that could be very important to the proper application of the provided geotechnical design/construction recommendations. This report should be read in its entirety prior to implementation into design and construction. F&R performed 20 soil test borings to depths ranging from 8 to 33.7 feet. The borings predominantly encountered low to highly plastic clayey and silty soils with minor amounts of fine sand. The consistency of the soils ranged from firm to very hard. Soft soils were not encountered in the borings. The moisture condition of the recovered soil samples typically was dry to moist. Wet soils were only noted in isolated zones in three of the borings. Groundwater was only encountered in two of the borings and at depths of greater than 10 feet. It is not anticipated that groundwater will be encountered during site grading or foundation construction activities. However, due to the presence of impervious silt and clay soils, trapped/perched water conditions should be anticipated during periods of inclement weather and during seasonally wet periods. Partially Weathered Rock (PWR) was encountered in 7 of the 20 borings. The depth to PWR varied from 2.5 to 14 feet. Auger refusal was encountered in only one boring at a depth of 8 feet and is anticipated to represent the bedrock surface. Based on the proposed grading, we do not anticipate that PWR or rock will be encountered during mass grading. However, PWR or rock could be encountered in deeper utility excavations, particularly on the east side of the site. It is our opinion that the subsurface conditions are suitable for the proposed development from a geotechnical engineering perspective. Stiff residual soils and properly compacted structural fill are suitable to support the structure on shallow spread foundations designed using a net allowable bearing capacity of 3,000 psf. The near surface highly plastic clays and clayey silts encountered in 14 of the 20 borings are considered poor material for use as structural fill and poor subgrade materials. These soils are highly moisture sensitive, frequently difficult to properly place and compact, and become unstable during normal construction activities when wet. It is recommended that highly plastic soils be used in non-load bearing areas or in the lower portion of deeper roadway fills. These soils are also not desirable subgrade soils, and if present at finished subgrades, undercutting and repair with lower plasticity materials will be required to create suitable subgrades. The borings also encountered lower plasticity silts and clays (USCS ML and CL soils). Although these lower plasticity soils are still moisture sensitive, they are generally considered fair to good materials for use as structural earth fill and are suitable subgrades for pavements, slabs and foundations. If earthwork is performed during the seasonally wet winter months, additional subgrade undercutting and repair will likely be required and it may be more difficult to properly compact structural fill than if earthwork is performed during the seasonally dryer months. Chatham County Chatham County Jail F&R Project No. 66N-0097 November 16,

6 1.0 PURPOSE & SCOPE OF SERVICES The purpose of the subsurface exploration and geotechnical engineering evaluation was to explore the subsurface conditions in the area of the proposed Chatham County Jail development and to provide geotechnical engineering recommendations that can be used during the design and construction phases of the project. F&R s scope of services included the following: Completion of 20 soil test borings to depths ranging from 8 to 33.7 feet below the existing ground surface; Preparation of typed Boring Logs and development of Subsurface Profiles; Performing geotechnical laboratory testing on representative soil samples; Performing a geotechnical engineering evaluation of the subsurface conditions with regard to their suitability for the proposed construction; Preparation of this geotechnical report by professional engineers. 2.0 PROJECT INFORMATION 2.1 Site Location and Description The project site is located on the west side of County Landfill Road, approximately 3,000 feet north of its intersection with US Highway 64 in Pittsboro, Chatham County, North Carolina. The project site consists of approximately 10 acres of undeveloped wooded land, which is situated on a larger 26 acre parcel that is owned by Chatham County. The project site generally slopes down from the north and east to the southwest corner at grades typically ranging from about 5 to 10 percent. The highest elevation of the site is about 500 along the east property line and the lowest elevation is about 466 at the southwest corner, which equates to a topographic relief of about 34 feet across the 10 acre site. Two ephemeral drainage channels are located just beyond the proposed development limits at the southwest corner of the site. Shallow drainage features or swales (topographic depressions) extend from the ephemeral channel to the northeast and across the building area. Water was not Chatham County Chatham County Jail F&R Project No. 66N-0097 November 15,

7 present in the ephemeral channels or in the drainage features at the time of F&R s site reconnaissance. 2.2 Proposed Construction Information regarding proposed site layout and grading was provided by Landworks Design Group, P.A.; a portion of the site grading plan is presented as Figure No. 1 in Appendix I. Structural loading information was provided by Browning Engineers, Inc. via dated November 7, The proposed building will consist of a one and two-story, load-bearing masonry structure with a slab-on-grade floor. Based on our review of the provided plans, the building will be approximately 400 feet long and range in width from about 70 to 175 feet; the building footprint covers approximately 45,000 ft 2. The building will have a finished floor elevation (FFE) of 483. Existing site grades within the building range from approximately 476 to 487. As such, maximum earth cuts and fills of 4 and 7 feet, respectively, are anticipated to establish the FFE. The estimated column loads range between 150 and 215 kips and the estimated uniform wall loads range between 3.5 and 5.5 kips per linear foot (klf). A depressed loading dock will be located at the west end of the north building wall; the ground surface at the loading dock will be 4 feet below the FFE (i.e., at Elevation 479). Paved drive and parking areas are located on the north and south sides of the building. Based on review of proposed grading, maximum earth cuts and fills of approximately 8 feet are anticipated in these areas. Cut and fill slopes are located along the north, west and south margins of the project site. The slopes are 10 feet or less in height. Based on our review of the grading plan, it appears that most of the cut and fill slopes are proposed to be graded between 2.5H:1V and 3.5H:1V. Two BMP s are proposed; one is located near the southwest corner of the site (BMP #1) and the other is located on the west side of the site (BMP #2). Chatham County Chatham County Jail F&R Project No. 66N-0097 November 15,

8 3.0 EXPLORATION PROCEDURES 3.1 Subsurface Exploration F&R advanced a total of 20 soil test borings (B-1 to B-20) as part of this exploration at the approximate locations shown on the Boring Location Plan presented as Figure No. 1 in Appendix I. The borings were advanced to depths ranging from 8 to 33.7 feet. The test boring locations were established in the field by F&R using a hand held GPS unit. F&R was informed by Landworks Design Group, P.A. that the project surveyor confirmed the boring locations and those locations are shown on the Boring Location Plan. Ground surface elevations at the boring locations were interpolated from the existing topographic information presented on the previously referenced grading plan provided to F&R. Given the method of determination, the ground surface elevations should only be considered approximate. The test borings were advanced by an ATV mounted drill rig using 2-1/4 inside diameter (I.D.) hollow stem augers for borehole stabilization. Representative soil samples were obtained using a standard two-inch outside diameter (O.D.) split barrel sampler in general accordance with ASTM D 1586, Penetration Test and Split-Barrel Sampling of Soils (Standard Penetration Test). The number of blows required to drive the split barrel sampler three consecutive 6-inch increments with an automatic hammer is recorded and the blows of the last two 6-inch increments are added to obtain the Standard Penetration Test (SPT) N-values representing the penetration resistance of the soil. Standard Penetration Tests were performed almost continuously to a depth of 10 feet and at a nominal interval of approximately 5 feet thereafter. An automatic hammer was used to perform the Standard Penetration Test (SPT) on this project. Research has shown that the Standard Penetration Resistance (N-value) determined by an automatic hammer is different than the N-value determined by the safety hammer method. Most correlations that are published in technical literature are based on the N-value determined by the safety hammer method. This is commonly termed N 60 as the rope and cathead with a safety hammer delivers about 60 percent of the theoretical energy delivered by a 140-pound hammer falling 30 inches. Several researchers have proposed correction factors Chatham County Chatham County Jail F&R Project No. 66N-0097 November 15,

9 for the use of hammers other than the safety hammer to correct the values to be equivalent to the safety hammer SPT N 60 -values. The correction is made using the following equation: N 60 = N field x C E N field is the value recorded in the field and C E is the drill rod energy ratio for the hammer utilized in the field. When using an automatic hammer, it is recommended that a correction factor (C E ) of 1.3 be utilized to covert N field values to N 60 values in accordance with guidelines provided in the Performance and Use of the Standard Penetration Test in Geotechnical Engineering Practice manual published by the Center for Geotechnical Practice and Research at the Virginia Polytechnical Institute and State University. The N-values reported on the Boring Logs and Subsurface Profiles included in this report are the actual, uncorrected, field derived values (N field ). It is recommended that corrected N 60 values be used for engineering analysis. A representative portion of the soil was obtained from each SPT sample, sealed in an eight-ounce glass jar, labeled and transported to our laboratory for final classification and analysis by a geotechnical engineer. The soil samples were classified in general accordance with the Unified Soil Classification System (USCS), using visual-manual identification procedures (ASTM D2488). A Boring Log for each test boring is presented in Appendix II. Groundwater level measurements were obtained from the boreholes immediately after drilling (IAD) and after a stabilization period of approximately 24 hours. Temporary groundwater observation wells were installed in borings B-1, B-9, B-10, B-15, B-17 and B-20 to facilitate obtaining stabilized groundwater measurements. The temporary observation wells consisted of 1-inch diameter, hand-slotted PVC pipes installed into the completed borings. The annulus of each piezometer was backfilled with soil cuttings. Chatham County Chatham County Jail F&R Project No. 66N-0097 November 15,

10 3.2 Laboratory Testing F&R selected seven soil samples and subjected them to routine geotechnical index testing consisting of Natural Moisture Content, Sieve Analysis (% passing the #200 sieve) and Atterberg Limits determinations. The purpose of the index testing was to aid in our classification of the soil samples and development of engineering recommendations. In addition, a bulk soil sample was obtained and subjected to Standard Proctor testing and CBR testing to aid in the pavement design recommendations. The laboratory testing was performed in general accordance with applicable ASTM standards. The laboratory test results are presented in Appendix III of this report. 4.0 REGIONAL GEOLOGY & SUBSURFACE CONDITIONS 4.1 Regional Geology The project site is located in the Carolina Slate Belt of the Piedmont Physiographic province of North Carolina. This area generally consists of hills and ridges that are intertwined with an established system of draws and streams. The bedrock found in this area is mapped as Felsic Metavolcanic Rock. The virgin soils encountered in this area are the residual product of in-place chemical weathering of rock that was similar to the rock presently underlying the site. In areas not altered by erosion or disturbed by the activities of man, the typical residual soil profile consists of clayey soils near the surface, where soil weathering is more advanced, underlain by silts and sandy silts above partially weathered rock and bedrock. The boundary between soil and rock is not sharply defined. This transitional zone termed Partially Weathered Rock is typically found overlying the parent bedrock. Partially Weathered Rock (PWR) is defined, for engineering purposes, as residual material exhibiting Standard Penetration Resistances in excess of 100 blows per foot (bpf). Weathering is facilitated by fractures, joints and by the presence of less resistant rock types. Consequently, the profile of the PWR and hard rock is quite irregular and erratic, even over short horizontal distances. Commonly, lenses and boulders of hard rock and zones of PWR can be encountered within the soil mantle, well above the general bedrock level. Chatham County Chatham County Jail F&R Project No. 66N-0097 November 15,

11 4.2 Subsurface Conditions General The subsurface conditions discussed in the following sections and those shown on the attached Boring Logs represent an estimate of the subsurface conditions based on interpretation of the boring data using normally accepted geotechnical engineering judgments. The transitions between different soil strata are usually less distinct than those shown on the boring logs. Sometimes the relatively small sample obtained in the field is insufficient to definitively describe the origin of the subsurface material. Although individual soil test borings are representative of the subsurface conditions at the boring locations on the dates shown, they are not necessarily indicative of subsurface conditions at other locations or at other times. Data from the specific soil test borings are shown on the attached Boring Logs presented in Appendix II of this report. Subsurface Profiles have been prepared from the boring data to graphically illustrate the subsurface conditions encountered at the site. The Subsurface Profiles are presented as Figures 2 and 3 in Appendix I Surficial Materials Surficial Organic Soils were encountered in the test borings from the ground surface to depths of approximately 0.2 to 0.5 feet. The Surficial Organic Soils generally consisted of brown fine sandy silt with roots, fibrous matter, and/or other organic materials. In some of the borings, roots were encountered below the Surficial Organic Soil extending to depths of approximately 2 feet. Surficial Organic Soil is generally unsuitable for engineering purposes. F&R has not performed any laboratory testing to determine the organic content or other horticultural properties of the observed Surficial Organic Soil materials. Therefore, the term Surficial Organic Soil is not intended to indicate suitability for landscaping and/or other purposes. The Surficial Organic Soil depths provided in this report are based on driller observations and should be considered approximate. We note that the transition from Surficial Organic Soil to underlying materials may be gradual, and therefore the observation and measurement of Surficial Organic Soil depths is subjective. Actual Surficial Organic Soil depths should be expected to vary. Chatham County Chatham County Jail F&R Project No. 66N-0097 November 15,

12 4.2.3 Residual Soils The native soils consisted of variations of low to high plasticity clays and silts with varying minor amounts of fine sand (USCS ML, CL, MH and CH soils). The consistency of the soils typically ranged from stiff to very hard. Firm consistency soils (SPT N-values of 5 to 7 blows per foot bpf) were only noted in the upper 2 feet of borings B-8, B-9, B-12, B-17 and B-19). Soft soils (i.e., soils with SPT N-values of 4 bpf or less) were not encountered in any of the borings. Highly plastic clays and silty clays (USCS MH/CH, CH and MH soils) were encountered in 11 of the borings beneath the Surficial Organic Soil and extending to depths ranging from 2 to 6.5 feet (average depth of 2.5 feet). In addition, deeper layers (2 to 4 feet thick) of highly plastic soils were also noted in 5 borings in the upper 12 feet of the soil profile. The consistency of the highly plastic soils typically ranged from stiff to very stiff, with firm consistencies only noted in the upper 2 feet of B-17 and B-19. Layers of very stiff the very hard, moderately plastic clayey silts (USCS ML/MH) were noted in 5 borings. In borings B-3, B-14, B-16 and B-18, these soils were in a layer about 4.5 to 7 feet thick in the upper 10 feet of the soil profile. In boring B-19, these ML/MH clayey silts were encountered from a depth of 2 feet to termination at a depth of 20 feet. The remaining soils encountered in the borings consisted of low plasticity silts and clays (USCS ML and CL). The consistency of the low plasticity soils typically ranged from stiff to very hard, with firm consistency soils (SPT N-values of 5 blows per foot bpf) only noted in the upper 2 feet of borings B-8, B-9 and B Partially Weathered Rock & Auger Refusal Partially Weathered Rock (PWR) was encountered in 7 of the 20 soil test borings and sampled as very hard sandy silt with rock fragments and pieces of rock. The depth to PWR varied from as shallow as 2.5 feet in B-11 to as deep as 14 feet in B-20. The PWR typically extended from these depths to boring termination. However, in borings B-13, B-17 and B-20, inclusions Chatham County Chatham County Jail F&R Project No. 66N-0097 November 15,

13 (layers) of hard to very hard silt were encountered within the PWR. The SPT N-values in the PWR ranged from 50/0.5 to 50/5.5. Auger refusal was encountered only in boring B-8, at a depth of 8 feet. Auger refusal is a designation applied to any material that cannot be penetrated by the soil auger and typically includes boulders, hard rock lenses/ledges and bedrock. The nature of auger refusal was not explored in this boring, but is anticipated to represent the bedrock surface. 4.3 Soil Moisture and Groundwater Conditions In general, the recovered soil samples were dry to moist extending from the ground surface to boring termination. Wet soils were encountered only in 3 of the 20 test borings: B-9 from 6.5 to 8.5 feet, B-13 from 12 to 17 feet, and B-16 from 8 to 12 feet. Groundwater level measurements were recorded in the test borings upon completion of drilling and after a stabilization period of at least 24-hours. Groundwater was not present in any of the test borings immediately following drilling activities. Stabilized groundwater was noted only in two borings: B-9 at a depth of 18.7 feet and B-15 at a depth of 29.3 feet below the existing ground surface. As such, it is not anticipated that groundwater will be encountered during mass grading activities based on our understanding that maximum earth cuts will be generally less than 8 to 10 feet. However, due to the presence of relatively impervious silt and clay soils on the project site, trapped or perched water conditions should be anticipated during periods of inclement weather and during seasonally wet periods. It should be noted that groundwater levels fluctuate depending upon seasonal factors such as precipitation and temperature. As such, soil moisture and groundwater conditions at other times may vary or be different from those described in this report. Chatham County Chatham County Jail F&R Project No. 66N-0097 November 15,

14 5.0 GEOTECHNICAL DESIGN RECOMMENDATIONS 5.1 General Development Considerations The conclusions and recommendations contained in this section of the report are based upon the results of the 20 soil test borings performed by F&R, laboratory test results, our experience with similar subsurface conditions and projects, and the information provided regarding the proposed development. It is our opinion that the subsurface conditions encountered at the project site are suitable for the proposed development from a geotechnical engineering perspective provided the recommendations presented in subsequent sections of this report are followed throughout the design and construction phases of this project. Stiff residual soils and properly placed and compacted structural fill should be suitable for support of the proposed structure on conventional shallow spread foundations. The near surface highly plastic clays and clayey silts (USCS MH/CH, CH and MH soils) encountered in 14 of the 20 borings performed across the site are generally considered poor material for use as structural fill and poor subgrade materials for foundations, slabs and pavements. These soils are highly moisture sensitive. As a result of being highly moisture sensitive, these soils are frequently difficult to properly place and compact, and become unstable during normal construction activities when wet. As such, if these soils are excavated from cut areas, it is generally recommended that they be used in non-load bearing areas or in the lower portion of deeper roadway fills. The highly plastic soils are also not desirable subgrade soils, and if present at finished subgrade (e.g., roadway and building pad subgrades), undercutting and repair with lower plasticity materials will be generally required to create suitable subgrades for pavement and building construction. Although layers of highly plastic soils were encountered in some areas, the borings also encountered lower plasticity silts and clays (USCS ML and CL soils). Although these lower plasticity soils are still moisture sensitive, they are generally considered good to fair materials for use as structural earth fill and are suitable subgrades for pavements, slabs and foundations. Chatham County Chatham County Jail F&R Project No. 66N-0097 November 15,

15 Due to the moisture sensitivity of the on-site soils, it is strongly recommended that earthwork operations be performed during the seasonally drier months (typically May to October) when weather conditions are more conducive to moisture conditioning of earth fill and achieving proper compaction of structural fill. If earthwork is performed during the seasonally wet months, additional subgrade undercutting and repair will likely be required and it may be difficult to properly compact structural fill. Based on our review of the provided site grading plan, we do not anticipate that Partially Weathered Rock (PWR) will be encountered during mass grading. However, depending upon utility invert elevations, it is possible that PWR could be encountered in deeper utility excavation, particularly on the eastern side of the project site. Detailed recommendations regarding PWR excavation will be provided in a subsequent section of this report. 5.2 Foundation Design The project site is suitable to support the proposed structure on conventional shallow spread foundations provided the site preparation and fill placement recommendations presented in this report are followed. For foundations bearing on stiff residual soils or properly compacted structural fill overlying approved residual materials, F&R recommends the use of a net allowable soil bearing pressure of 3,000 pounds per square foot (psf) for the design of foundations. Spread foundations should bear directly upon approved structural fill or residual soils and should be embedded at least 24 inches below adjacent exterior grades for bearing capacity and frost protection considerations. Final foundation sizes should be determined by the project structural engineer based on actual design loads, building code requirements and other structural considerations. For foundations designed and constructed in accordance with the recommendations provided in this report, we have estimated that maximum settlements will be on the order of 1 to 1.25 inches or less. We anticipate that such settlements would be structurally acceptable; however, this should be determined by the Project Structural Engineer. Chatham County Chatham County Jail F&R Project No. 66N-0097 November 15,

16 Based on the soil profile encountered at the site (generally stiff to hard residual soils over very hard PWR material), it is our opinion that a seismic design Site Class C as presented in the 2009 NC Building Code should be used for structural design purposes. 5.3 Slab-on-Grade Floors Ground floors may be designed as a slab-on-grade. We recommend that a modulus of subgrade reaction (k) of 150 pounds per cubic inch (pci) be used for slab design. The subgrade soils for support of floor slabs should be prepared as outlined in subsequent sections of this report. Utility and other construction excavations performed in the prepared floor slab subgrade should be backfilled with properly compacted structural fill in accordance with subsequently referenced structural fill criteria to aid in providing uniform slab support. The floor slab should be supported on at least 4 inches of NCDOT ABC Stone to provide a uniformly well-compacted material immediately beneath the slab. The floor slab should be underlain by a vapor retarder to reduce the potential for floor slab dampness. Vapor retarder construction should be performed in accordance with applicable ACI guidelines. Floor slab design and construction should incorporate isolation joints around columns, utility penetrations, and along bearing walls to allow for differential movement to occur without damage to the floor. To reduce the risks of unsightly slab cracking, F&R recommends that concrete quality control testing be performed during concrete placement, control joints (as designed by the structural engineer) be cut into the slab as soon as possible after the concrete placement, and the slab be cured as appropriate for the prevailing weather conditions (temperature, humidity and wind velocity). Final slab design should be determined by the project structural engineer based on actual design loads, building code requirements and other structural considerations. 5.4 Retaining Walls The depressed loading dock wall located along the north side of the building will be a laterally loaded retaining wall of cast-in-place concrete construction. F&R is not aware of any other laterally loaded retaining walls on this project. Chatham County Chatham County Jail F&R Project No. 66N-0097 November 15,

17 Since the loading dock retaining wall will be integral to the building wall and structural system, F&R assumed that it will be restrained from movement and therefore should be designed to resist at-rest lateral earth pressures. Assuming the wall will be backfilled with low plasticity onsite materials (USCS CL or ML soils), the wall should be designed using an at-rest coefficient (K o ) of Assuming a moist backfill unit weight of 115 pounds per cubic foot (pcf), F&R recommends that an at-rest earth pressure equivalent fluid weight (EFW) of 65 pcf be used in design. Highly plastic clay or clayey silt soils should not be used as backfill for retaining walls. Should retaining walls that are allowed to rotate at the top be considered for this project (e.g., free standing exterior walls), F&R should be contacted to provide earth pressure coefficients and equivalent fluid weights. Lateral earth pressures arising from surcharge loading, foundations in the backfill zone, earthquake loading and groundwater should be added to the above soil earth pressures to determine the total lateral earth pressure, which the walls must resist. In addition, transient loads imposed on the walls by construction equipment during backfilling should be taken into account during design. Compaction of backfill behind the walls should be on the order of 95 percent of the Standard Proctor maximum dry density in structural areas. In non-structural areas, backfill compaction can be reduced to 92 percent. Excessive compaction may cause damage to the walls. Walls should be adequately braced during compaction of the wall backfill. Heavy compaction equipment should not be allowed within 10 feet of the walls. Although groundwater is not expected above the base of the retaining walls on a permanent basis, we recommend that laterally loaded walls be provided with a drainage system to maintain the wall backfill in a drained condition at all times such that the walls are not subject to hydrostatic pressures. We recommend that a one-foot wide zone of free-draining washed stone be constructed adjacent to the back of the walls and extend down to a foundation drain (perforated drain pipe). A geotextile filter fabric (Mirafi 180N or equivalent) should be placed between the washed stone drainage layer and the remaining backfill material. The foundation Chatham County Chatham County Jail F&R Project No. 66N-0097 November 15,

18 drain should be positively graded to allow drainage of any water that may collect in the wall backfill. It is assumed that the collection drain will be designed for gravity discharge of collected seepage in the backfill. It is recommended that the fabric encased washed stone extend to within approximately 2 feet of the ground surface and covered with more impermeable silty clayey soils in order to help prevent surface runoff or infiltration from rainfall being directed into the wall drain backfill. Alternatively, a geo-composite drainage material such as Miradrain 6000 may be installed against the wall and connected to an appropriately designed footing drain to suitably outlet collected water. The foundation drain should be positively graded to allow drainage of any water that may collect in the wall backfill. 5.5 Pavement Design Subgrade preparation in the proposed pavement areas should be performed as will be outlined in subsequent sections of this report. The design pavement section is dependent upon the anticipated traffic and soil subgrade strength. The results of the laboratory CBR testing indicated a soaked CBR value of about 1.5. Published CBR values for fine grained soils similar to those at the project site range from 2 to 5. These are considered to be low CBR values and indicative of soils that are relatively poor subgrade materials. As such, F&R used a design CBR value of 2 in our pavement analysis. Specific traffic information was not available for this project. The project will have paved car parking areas as well as driveways on the north and south sides of the site. The driveway on the north side of the site leads to the loading dock. F&R performed pavement designs using NCDOT Interim Pavement Design Procedure based on a design life of 20 years. Although traffic information was not available, F&R assumes that the driveways and travel lanes could receive occasional light and heavy truck traffic. We have assumed a daily traffic count of 200 cars, 4 light trucks and 1 heavy truck in our analysis for drives and travel lanes, which is equal to approximately 3.8 daily 18-kip equivalent single axle loads (ESAL). For the parking areas, F&R utilized a traffic volume of approximately 0.5 daily 18-kip ESAL, which assumes only car traffic and no truck traffic. Chatham County Chatham County Jail F&R Project No. 66N-0097 November 15,

19 Based on the above subgrade parameters and assumed traffic volumes, we recommend the following flexible pavement section over a prepared subgrade: Traffic NCDOT Asphalt Concrete Surface, Type SF9.5A NCDOT Asphalt Concrete Intermediate Course, Type I 19.0 B NCDOT ABC Base Course Thickness Total Thickness Medium Duty - Driveway Areas Light Duty - Car parking areas - No truck traffic ** ** F&R recommends that a non-woven geotextile filter fabric (Mirafi 180N or equivalent) be placed on the soil subgrade prior to placement of ABC stone base course in the more highly traveled driveway areas. The filter fabric will help to maintain separation between the silty/clayey subgrade soils and the ABC stone and prevent contamination of the ABC stone. We recommend that rigid concrete pavement be utilized in dumpster areas or other areas subjected to concentrated loading. The concrete pavement should consist of at least 6 inches of 5,000 psi air-entrained concrete over a 6 inch thick base course of compacted ABC stone. We emphasize that good base course drainage is essential for successful pavement performance. The ABC stone should be maintained in a drained condition at all times. Water build-up in the base course could result in premature pavement failures. Proper drainage may be aided by grading the site such that surface water is directed away from pavements and construction of swales adjacent to pavements. All pavements should be graded such that surface water is directed towards the outer limits of the paved area or to catch basins located such that surface water does not remain on the pavement. Flexible asphalt pavements, concrete pavements, and bases should be constructed in accordance with the guidelines of the latest applicable North Carolina Department of Transportation Standard Specifications for Roads and Structures. Materials, weather limitations, placement and compaction are specified under appropriate sections of this publication. Concrete pavement construction should be in accordance with applicable American Concrete Institute (ACI) guidelines. Chatham County Chatham County Jail F&R Project No. 66N-0097 November 15,

20 5.6 Cut and Fill Slopes Based on our review of the provided grading plan, it appears that project site cut and fill slopes will be less than 10 feet high and are designed at grades ranging from 2.5H:1V to 3.5:H:1V. It is F&R s opinion that these slopes will be stable from a slope stability standpoint provided the fill slopes are constructed on stable subgrade with properly compacted and tested structural fill materials. Fill slopes should be over built and then cut back to assure the slope face is well compacted material. The top of slopes should be located a minimum of 10 feet from structural limits. The slopes should be vegetated as soon as possible to minimize surface sloughing and erosion. However, seepage and surface runoff may cause the slopes to slough and erode resulting in shallow surface failures. A swale or shallow ditch should be constructed near the top of slopes to prevent surface water from flowing onto the slopes. We recommend that all cut and fill slopes be observed by a geotechnical engineer or his representative during construction. Additional slope drainage and protection measures may be required in certain areas depending upon conditions observed at the time of slope construction. 6.0 GEOTECHNICAL CONSTRUCTION RECOMMENDATIONS 6.1 Site Preparation After clearing and grubbing, all surficial organic soils, roots, vegetation and any other deleterious materials should be stripped from the building and pavement areas. The stripping should extend a distance of at least 5 feet beyond the building perimeters, but not less than the area within a 2H:1V slope projecting down to original grade from the perimeter footings or building pad in fill areas, whichever is greater. Following the stripping of deleterious material from proposed structural areas, the exposed subgrade soils at the finished subgrade level and in fill sections should be proofrolled with a loaded tandem axle dump truck, scraper, or other similar type of construction equipment to confirm the stability of the subgrade soils. The proofroll operations should be observed by a Chatham County Chatham County Jail F&R Project No. 66N-0097 November 15,

21 geotechnical engineer or his representative. If proofrolling reveals unstable conditions, the method of repair should be as directed by the project geotechnical engineer. Methods of repair may include, but are not necessarily limited to drying and re-compaction; undercutting and replacement with suitable structural fill; use of geo-textiles and/or geo-grids with select fill; use of lime stabilization, or other methods deemed appropriate by the project geotechnical engineer. Based on the results of the test borings, the subgrade soils are expected to be firm to stiff, although relatively soft soils (SPT N-values of 5 bpf) were noted in the upper 2 feet of a few borings and could be encountered in unexplored areas of the site. Even though the subgrade soil are anticipated to be relatively firm, they are moisture sensitive and will become soft when exposed to water. As such, subgrade conditions could be different at the time of construction as a result of prevailing weather conditions or if exposed to inclement weather during site earthwork activities. As such, F&R anticipates that some undercut/repair work will be required to establish stable subgrades. As reported earlier in this report, high plasticity soils (MH/CH, CH and MH soils) were encountered in 14 of the borings, primarily in the upper few feet of the soil profile. These soils are highly moisture sensitive and can undergo volume changes (shrink/swell) with changes in moisture content. These soils are generally considered to be poor subgrade and subgrade grade materials. Due to the moisture sensitivity, shrink/swell potential and poor subgrade/bearing grade characteristics, F&R recommends that a minimum of 2 feet of separation be maintained between stable high plasticity soils and proposed subgrades for pavement and building areas. In order to create this separation, undercutting highly plastic soils and replacement with lower plasticity soils will likely be required in some areas. Pavement and roadway subgrades should consist of low plasticity soils. Chatham County Chatham County Jail F&R Project No. 66N-0097 November 15,

22 6.2 Structural Fill Placement and Compaction It is expected that the low to moderately plastic on-site cut soils can be used as structural fill material. Low to moderately plastic soils are generally considered fair to good materials for use as structural earth fill. As previously indicated, highly plastic clayey and clayey silt soils (USCS MH/CH, CH and MH soils) are considered poor materials for re-use as structural fill and it is recommended that they be used in non-load bearing landscaped areas or in the lower portions of deep roadway fills. A majority of the soils encountered in the test borings were dry to moist; however, wet soils were encountered in a few isolated areas. Depending upon the site and prevailing weather conditions at the time of construction, some soils may require moisture conditioning (drying of wet soils or wetting of dry soils) prior to use as structural fill. As such, it is recommended that earthwork be performed during the summer months when weather conditions are more conducive to moisture conditioning of fill materials. All structural earth fill should be compacted at a moisture content within +3 percent of the optimum moisture content. All structural earth fill (i.e., fill placed in load bearing areas or slopes) should be placed in loose lifts not exceeding 8 inches and be compacted to at least 95 percent of the Standard Proctor maximum dry density as determined by ASTM D-698. The top 12 inches of fill should be compacted to at least 98 percent of the Standard Proctor maximum dry density. All areas requiring grade increases that are steeper than a slope of 4H:1V should be plowed, stepped and leveled to assure that fill is placed on near level surfaces. All structural fill material should be placed and compacted under the full-time observation of a qualified geotechnical engineer or engineering technician working under the direction of the geotechnical engineer. The placement and compaction of all fill material should be tested at frequent intervals in order to confirm that the recommended degree of compaction is achieved. As previously stated, the on-site soils have sufficient silt/clay content to render them moisture sensitive. The on-site soils will become unstable (i.e., pump and rut) during normal construction activities when in the presence of excess moisture. Soils with a moisture content greater than 3 Chatham County Chatham County Jail F&R Project No. 66N-0097 November 15,

23 percent above the optimum moisture content are generally considered to have excessive moisture. During earthwork and construction activities, surface water runoff must be drained away from the construction areas to prevent water from ponding on or saturating the soils within excavations or on subgrades. This is especially important considering the moisture sensitivity of the soils at this site. Excavated, ripped or blasted PWR and rock may also be used as structural fill material. Special placement and compaction procedures for the PWR and other rock materials should be provided by the project geotechnical engineer prior to earthwork. All structural fill (soil/pwr/rock) placement and compaction activities should be observed on a full-time basis by a geotechnical engineer or qualified engineering technician working under the supervision of the geotechnical engineer. 6.3 PWR Excavation Based on the results of the test borings, we do not anticipate that PWR will be encountered during mass grading activities. However, some PWR could be encountered in deeper utility line excavations, particularly on the east side of the project site. Once final utility plans are available, the magnitude of potential PWR excavation can be determined for utility trenches. If PWR is encountered in mass grading areas, heavy excavating equipment with ripping tools (e.g., D-8 dozer with single shank ripper) is typically effective in removing softer PWR (i.e., PWR with N-values of 50/4 to 50/6 ). However, removal of harder PWR (i.e., PWR with N-values of 50/0 to 50/3 ) and hard rock during mass grading in open areas will not likely be possible with ripping equipment and may require hammering, chipping or blasting. Removal of softer PWR from confined excavations (e.g., utility excavations) may be able to be accomplished using a large track hoe (e.g., CAT 330 with rock teeth); however, excavation will likely be slow and light blasting is typically performed to pre-loosen the PWR. Removal of harder PWR and hard rock in confined excavations will not likely be possible with conventional equipment and typically requires blasting. The speed and ease of PWR and rock excavation will depend upon the equipment utilized, experience of the equipment operators and geologic structure of the PWR. Chatham County Chatham County Jail F&R Project No. 66N-0097 November 15,

24 6.4 Foundation Construction Recommendations We recommend that the footing excavations be observed by a qualified geotechnical engineer or his representative prior to placement of reinforcing steel and concrete. The purpose of the engineering observation would be to determine that the foundations bear in suitable soils at the proper embedment depths, and that unsuitable soft or loose materials are undercut and backfilled with approved structural fill material. Hand auguring and Dynamic Cone Penetrometer (DCP) testing should be performed at the direction of the project geotechnical engineer to verify the consistency of the bearing soils and underlying support soils. It is recommended that a smooth bladed backhoe bucket be used to remove the final 6 to 12 inches of soils above the foundation bearing grade in order to prevent disturbing soils below the bearing grade and/or prevent gouging narrow grooves in the bearing grade as may occur with a toothedend bucket. It is anticipated that highly plastic clayey and clayey silt soils (MH/CH, CH & MH soils) may be encountered at the foundation bearing grade in some areas of the building, particularly in areas where the bearing grades fall within the upper few feet of the native soil profile. If highly plastic soils are encountered at the footing bearing grade elevation, undercutting and repairing of footing bearing grades may be required. Undercutting and repair of footing subgrades will also be required if soft soils are encountered at the footing bearing level. If undercutting is performed, the undercut excavations should be backfilled with materials approved by the project geot4echnical engineer. Some undercuts may be recommended to be backfilled with NCDOT No. 57 washed stone up to the planned bearing grade. The washed stone thickness should not exceed 2 feet before the surface of the washed stone is densified with a heavy vibratory plate compactor to the satisfaction of the geotechnical engineer or his representative. Exposure to the environment may weaken the soils at the footing bearing level if excavations remain open for long periods of time. The foundation bearing surface should be level or suitably benched and free of loose soil, ponded water and debris. If the bearing soils are softened by surface water intrusion or exposure, the softened soils must be removed from the foundation Chatham County Chatham County Jail F&R Project No. 66N-0097 November 15,

25 excavation immediately prior to placement of concrete. Foundation excavations must be maintained in a drained/de-watered condition throughout the foundation construction process. If the foundation excavations must remain open overnight, or if rainfall becomes imminent while the bearing soils are exposed, we recommend that a 2 to 4 inch thick mud mat of lean concrete (1,500 psi) be placed on the bearing soils before placing the reinforcing steel. In addition, F&R stresses the need for positive perimeter surface drainage around building areas to direct all runoff water away from buildings and foundations. 6.5 Temporary Excavation Recommendations Mass excavations and other excavations required for construction of this project must be performed in accordance with the United States Department of Labor, Occupational Safety and Health Administration (OSHA) guidelines (29 CFR 1926, Subpart P, Excavations) or other applicable jurisdictional codes for permissible temporary side-slope ratios and/or shoring requirements. The OSHA guidelines require daily inspections of excavations, adjacent areas and protective systems by a competent person for evidence of situations that could result in cave-ins, indications of failure of a protective system, or other hazardous conditions. All excavated soils, equipment, building supplies, etc., should be placed away from the edges of the excavation at a distance equaling or exceeding the depth of the excavation. F&R cautions that the actual excavation slopes will need to be evaluated frequently each day by the competent person and flatter slopes or the use of shoring may be required to maintain a safe excavation depending upon excavation specific circumstances. The contractor is responsible for providing the competent person and all aspects of site excavation safety. F&R can evaluate specific excavation slope situations if we are informed and requested by the owner, designer or contractor s competent person. 7.0 CONTINUATION OF SERVICES As previously discussed, the Geotechnical Engineer of record should be retained to observe and test earthwork activities, and subgrade preparations for slopes, foundations, floor slabs and pavements. It should be noted that the actual soil conditions at the various subgrade levels and Chatham County Chatham County Jail F&R Project No. 66N-0097 November 15,

26 footing bearing grades will vary across this site and thus the presence of the Geotechnical Engineer and/or his representative during construction will serve to validate the subsurface conditions and recommendations presented in this report. We also stress the importance of conducting hand auger and DCP testing in the footing excavations in order to confirm the anticipated subsurface conditions and define footings that should be undercut and repaired as outlined in this report. We recommend that F&R be employed to monitor the earthwork and foundation construction, and to report that the recommendations contained in this report are completed in a satisfactory manner. Our continued involvement on the project will aid in the proper implementation of the recommendations discussed herein. The following is a recommended scope of services: Review of project plans and construction specifications to verify that the recommendations presented in this report have been properly interpreted and implemented; Observe the earthwork process to document that subsurface conditions encountered during construction are consistent with the conditions anticipated in this report; Observe the subgrade conditions before placing structural fill including proofroll observations; Observe the placement and compaction of any structural fill and backfill, and perform laboratory and field compaction testing of the fill; and, Observe all foundation excavations and footing bearing grades for compliance with the recommended design soil bearing capacity. 8.0 LIMITATIONS This report has been prepared for the exclusive use of Chatham County and/or their agents, for specific application to the referenced project in accordance with generally accepted soil and foundation engineering practices. No other warranty, express or implied, is made. Our evaluations and recommendations are based on design information furnished to us; the data obtained from the previously described subsurface exploration program, and generally accepted geotechnical engineering practice. The evaluations and recommendations do not reflect variations in subsurface conditions which could exist intermediate of the boring locations or in unexplored Chatham County Chatham County Jail F&R Project No. 66N-0097 November 15,

27 areas of the site. Should such variations become apparent during construction, it will be necessary to re-evaluate our recommendations based upon on-site observations of the conditions. There are important limitations to this and all geotechnical studies. Some of these limitations are discussed in the information prepared by ASFE, which is included in Appendix IV. We ask that you please review this ASFE information. Regardless of the thoroughness of a subsurface exploration, there is the possibility that conditions between borings will differ from those at the boring locations, that conditions are not as anticipated by the designers, or that the construction process has altered the soil conditions. Therefore, experienced geotechnical engineers should evaluate earthwork, pavement, and foundation construction to verify that the conditions anticipated in design actually exist. Otherwise, we assume no responsibility for construction compliance with the design concepts, specifications, or recommendations. In the event that changes are made in the design or location of the proposed structures, the recommendations presented in the report shall not be considered valid unless the changes are reviewed by our firm and conclusions of this report modified and/or verified in writing. If this report is copied or transmitted to a third party, it must be copied or transmitted in its entirety, including text, attachments, and enclosures. Interpretations based on only a part of this report may not be valid. Chatham County Chatham County Jail F&R Project No. 66N-0097 November 15,

28 APPENDIX I FIGURES Chatham County Chatham County Jail F&R Project No. 66N-0097 November 16, 2011

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33 APPENDIX II BORING LOGS Chatham County Chatham County Jail F&R Project No. 66N-0097 November 16, 2011

34 KEY TO SOIL CLASSIFICATION Correlation of Penetration Resistance with Relative Density and Consistency Sands and Gravels Silts and Clays No. of Relative No. of Relative Blows, N Density Blows, N Density 0-4 Very loose 0-2 Very soft 5-10 Loose 3-4 Soft Medium dense 5-8 Firm Dense 9-15 Stiff Over 50 Very dense Very stiff Hard Over 50 Very hard Particle Size Identification Boulders: Cobbles: Gravel: Sand: Silt and Clay: (Unified Classification System) Diameter exceeds 12-in. (300-mm) 3-in. (75-mm) to 12-in. (300-mm) diameter Coarse - ¾-in. (19-mm) to 3 in. (75-mm) diameter Fine - No. 4 (4.75-mm) sieve to ¾-in. (19-mm) diameter Coarse No. 10 (2.0-mm) to No. 4 (4.76 mm) sieve Medium No. 40 (0.425-mm) to No. 10 (2.0-mm) sieve Fine - No. 200 (0.075-mm) to No. 40 (0.425-mm) sieve Less than No. 200 (0.075-mm) sieve Modifiers The modifiers provide our estimate of the amount of silt, clay or sand size particles in the soil sample. Approximate Content Modifiers Field Moisture Description 5%: Trace Dry Absence of moisture, dusty, dry to touch 5 to 10%: Few Moist Damp but no visible water 15 to 25%: Little Wet Visible free water, usually soil is below water table 30 to 45%: Some 50 to 100% Mostly Chatham County Chatham County Jail F&R Project No. 66N-0097 November 16, 2011

35 R Froehling & Robertson, Inc. BORING LOG Boring: B-1 (1 of 1) Project No: 66N-0097 Client: Chatham County Project: Chatham County Jail City/State: Pittsboro, North Carolina Elevation Depth Description of Materials (Classification) SURFICIAL ORGANIC SOIL: Brown fine sandy SILT with roots and organics. Firm, moist, reddish brown slightly fine sandy very clayey SILT (MH/CH). Stiff, moist, orangish tan slightly fine sandy clayey SILT (ML/CL). Stiff, moist, reddish brown slightly fine sandy clayey SILT (MH). Stiff to firm, moist, orangish tan slightly fine sandy SILT (ML). Boring terminated at 10.0 feet. Elevation: 492 ± Total Depth: 10.0' Boring Location: See Boring Location Plan * Sample Blows Sample Depth (feet) N-Value (blows/ft) Drilling Method: 2.25" ID HSA Hammer Type: Automatic Date Drilled: 10/5/11 Driller: J. Gilchrist Remarks GROUNDWATER DATA: IAD: Dry 24 Hrs: Dry BORING_LOG 66N-0097 BORING LOGS.GPJ F&R.GDT 11/17/11 *Number of blows required for a 140 lb hammer dropping 30" to drive 2" O.D., 1.375" I.D. sampler a total of 18 inches in three 6" increments. The sum of the second and third increments of penetration is termed the standard penetration resistance, N-Value.

36 R Froehling & Robertson, Inc. BORING LOG Boring: B-2 (1 of 1) Project No: 66N-0097 Client: Chatham County Project: Chatham County Jail City/State: Pittsboro, North Carolina Elevation Depth Description of Materials (Classification) SURFICIAL ORGANIC SOIL: Brown fine sandy SILT with roots and organics. Stiff to very stiff, moist, reddish brown, slightly fine sandy very clayey SILT (MH/CH). Very stiff, moist, orangish tan, slightly fine sandy clayey SILT (ML/CL). Stiff to very stiff, moist, tan to gray fine sandy SILT (ML). Boring terminated at 10.0 feet. Elevation: 493 ± Total Depth: 10.0' Boring Location: See Boring Location Plan * Sample Blows Sample Depth (feet) N-Value (blows/ft) Drilling Method: 2.25" ID HSA Hammer Type: Automatic Date Drilled: 10/5/11 Driller: J. Gilchrist Remarks GROUNDWATER DATA: IAD: Dry 24 Hrs: Dry (cave at 5.4') BORING_LOG 66N-0097 BORING LOGS.GPJ F&R.GDT 11/17/11 *Number of blows required for a 140 lb hammer dropping 30" to drive 2" O.D., 1.375" I.D. sampler a total of 18 inches in three 6" increments. The sum of the second and third increments of penetration is termed the standard penetration resistance, N-Value.

37 R Froehling & Robertson, Inc. BORING LOG Boring: B-3 (1 of 1) Project No: 66N-0097 Client: Chatham County Project: Chatham County Jail City/State: Pittsboro, North Carolina Elevation Depth Description of Materials (Classification) SURFICIAL ORGANIC SOIL: Brown fine sandy SILT with roots and organics. Stiff, moist, reddish brown slightly fine sandy clayey SILT (ML/MH) with occasional root. Very stiff, moist, orangish tan fine sandy clayey SILT (ML/MH). Hard, dry to moist, light tan to tan fine sandy SILT (ML). Boring terminated at 10.0 feet. Elevation: 483 ± Total Depth: 10.0' Boring Location: See Boring Location Plan * Sample Blows Sample Depth (feet) N-Value (blows/ft) Drilling Method: 2.25" ID HSA Hammer Type: Automatic Date Drilled: 10/5/11 Driller: J. Gilchrist Remarks GROUNDWATER DATA: IAD: Dry 24 Hrs: Dry (cave at 3.5') BORING_LOG 66N-0097 BORING LOGS.GPJ F&R.GDT 11/17/11 *Number of blows required for a 140 lb hammer dropping 30" to drive 2" O.D., 1.375" I.D. sampler a total of 18 inches in three 6" increments. The sum of the second and third increments of penetration is termed the standard penetration resistance, N-Value.

38 R Froehling & Robertson, Inc. BORING LOG Boring: B-4 (1 of 1) Project No: 66N-0097 Client: Chatham County Project: Chatham County Jail City/State: Pittsboro, North Carolina Elevation Depth Description of Materials (Classification) SURFICIAL ORGANIC SOIL: Brown fine sandy SILT with roots and organics. Stiff to hard, moist, light brown fine sandy silty CLAY (CL). Hard to very hard, dry to moist, tan sandy SILT (ML). Elevation: 486 ± Total Depth: 10.0' Boring Location: See Boring Location Plan * Sample Blows Sample Depth (feet) N-Value (blows/ft) Drilling Method: 2.25" ID HSA Hammer Type: Automatic Date Drilled: 10/5/11 Driller: J. Gilchrist Remarks GROUNDWATER DATA: IAD: Dry 24 Hrs: Dry (cave at 4.4') Boring terminated at 10.0 feet BORING_LOG 66N-0097 BORING LOGS.GPJ F&R.GDT 11/17/11 *Number of blows required for a 140 lb hammer dropping 30" to drive 2" O.D., 1.375" I.D. sampler a total of 18 inches in three 6" increments. The sum of the second and third increments of penetration is termed the standard penetration resistance, N-Value.

39 R Froehling & Robertson, Inc. BORING LOG Boring: B-5 (1 of 1) Project No: 66N-0097 Client: Chatham County Project: Chatham County Jail City/State: Pittsboro, North Carolina Elevation Depth 0.2 Description of Materials (Classification) SURFICIAL ORGANIC SOIL: Brown fine sandy SILT with roots and organics. Stiff to very stiff, moist, reddish brown slightly fine sandy very clayey SILT (MH/CH). Elevation: 486 ± Total Depth: 10.0' Boring Location: See Boring Location Plan * Sample Blows Sample Depth (feet) N-Value (blows/ft) Drilling Method: 2.25" ID HSA Hammer Type: Automatic Date Drilled: 10/5/11 Driller: D. Tignor Remarks GROUNDWATER DATA: IAD: Dry 24 Hrs: Dry (cave at 7') Very stiff to stiff, dry to moist, reddish brown slightly fine sandy clayey SILT (ML). Boring terminated at 10.0 feet BORING_LOG 66N-0097 BORING LOGS.GPJ F&R.GDT 11/17/11 *Number of blows required for a 140 lb hammer dropping 30" to drive 2" O.D., 1.375" I.D. sampler a total of 18 inches in three 6" increments. The sum of the second and third increments of penetration is termed the standard penetration resistance, N-Value.

40 R Froehling & Robertson, Inc. BORING LOG Boring: B-6 (1 of 1) Project No: 66N-0097 Client: Chatham County Project: Chatham County Jail City/State: Pittsboro, North Carolina Elevation Depth Description of Materials (Classification) SURFICIAL ORGANIC SOIL: Brown fine sandy SILT with roots and organics. Stiff, moist, orangish brown slightly fine sandy silty CLAY (CL). Very stiff, moist, orangish brown slightly fine sandy clayey SILT (MH). Elevation: 491 ± Total Depth: 10.0' Boring Location: See Boring Location Plan * Sample Blows Sample Depth (feet) N-Value (blows/ft) Drilling Method: 2.25" ID HSA Hammer Type: Automatic Date Drilled: 10/5/11 Driller: D. Tignor Remarks GROUNDWATER DATA: IAD: Dry 24 Hrs: Dry (cave at 7') Very stiff, dry to moist, tan slightly fine sandy SILT (ML). Boring terminated at 10.0 feet BORING_LOG 66N-0097 BORING LOGS.GPJ F&R.GDT 11/17/11 *Number of blows required for a 140 lb hammer dropping 30" to drive 2" O.D., 1.375" I.D. sampler a total of 18 inches in three 6" increments. The sum of the second and third increments of penetration is termed the standard penetration resistance, N-Value.

41 R Froehling & Robertson, Inc. BORING LOG Boring: B-7 (1 of 1) Project No: 66N-0097 Client: Chatham County Project: Chatham County Jail City/State: Pittsboro, North Carolina Elevation Depth Description of Materials (Classification) SURFICIAL ORGANIC SOIL: Brown fine sandy SILT with roots and organics. Very stiff, moist, brown to tan slightly fine sandy clayey SILT (ML/CL). Hard, moist, tan and light tan slightly fine sandy clayey SILT (ML). Elevation: 471 ± Total Depth: 10.0' Boring Location: See Boring Location Plan * Sample Blows Sample Depth (feet) N-Value (blows/ft) Drilling Method: 2.25" ID HSA Hammer Type: Automatic Date Drilled: 10/6/11 Driller: D. Tignor Remarks GROUNDWATER DATA: IAD: Dry 24 Hrs: Dry (cave at 7') Very stiff, moist, grayish tan fine sandy SILT (ML) with trace rock fragments. Very hard to hard, moist, brown fine sandy SILT (ML) with weathered rock fragments. Boring terminated at 10.0 feet /5" BORING_LOG 66N-0097 BORING LOGS.GPJ F&R.GDT 11/17/11 *Number of blows required for a 140 lb hammer dropping 30" to drive 2" O.D., 1.375" I.D. sampler a total of 18 inches in three 6" increments. The sum of the second and third increments of penetration is termed the standard penetration resistance, N-Value.

42 R Froehling & Robertson, Inc. BORING LOG Boring: B-8 (1 of 1) Project No: 66N-0097 Client: Chatham County Project: Chatham County Jail City/State: Pittsboro, North Carolina Elevation Depth Description of Materials (Classification) SURFICIAL ORGANIC SOIL: Brown fine sandy SILT with roots and organics. Firm, moist, light brown SILT (ML). Very stiff, moist, light brown slightly fine sandy silty CLAY (CH). Very stiff to very hard, moist, tan to grayish tan sandy SILT and quartz rock pieces (ML/GM). Auger refusal and boring terminated at 8.0 feet. Elevation: 478 ± Total Depth: 8.0' Boring Location: See Boring Location Plan * Sample Blows /5.5" Sample Depth (feet) N-Value (blows/ft) Drilling Method: 2.25" ID HSA Hammer Type: Automatic Date Drilled: 10/6/11 Driller: J. Gilchrist Remarks GROUNDWATER DATA: IAD: Dry 24 Hrs: Dry (cave at 4') BORING_LOG 66N-0097 BORING LOGS.GPJ F&R.GDT 11/17/11 *Number of blows required for a 140 lb hammer dropping 30" to drive 2" O.D., 1.375" I.D. sampler a total of 18 inches in three 6" increments. The sum of the second and third increments of penetration is termed the standard penetration resistance, N-Value.

43 R Froehling & Robertson, Inc. BORING LOG Boring: B-9 (1 of 1) Project No: 66N-0097 Client: Chatham County Project: Chatham County Jail City/State: Pittsboro, North Carolina Elevation Depth Description of Materials (Classification) SURFICIAL ORGANIC SOIL: Brown fine sandy SILT with roots and organics. Firm, moist, light brown SILT (ML). Stiff to very stiff, moist, grayish tan, slightly fine sandy SILT (ML). Elevation: 476 ± Total Depth: 19.3' Boring Location: See Boring Location Plan * Sample Blows Sample Depth (feet) N-Value (blows/ft) Drilling Method: 2.25" ID HSA Hammer Type: Automatic Date Drilled: 10/6/11 Driller: J. Gilchrist Remarks GROUNDWATER DATA: IAD: Dry 24 Hrs: 18.7' in PVC Pipe Stiff, moist to wet, brown, orangish brown and dark brown slightly fine sandy clayey SILT (MH). Very stiff, moist, tan to brown sandy SILT (ML) with rock fragments Hard to very hard, moist, light brown slightly fine sandy SILT (ML) Boring terminated at 19.3 feet /4" BORING_LOG 66N-0097 BORING LOGS.GPJ F&R.GDT 11/17/11 *Number of blows required for a 140 lb hammer dropping 30" to drive 2" O.D., 1.375" I.D. sampler a total of 18 inches in three 6" increments. The sum of the second and third increments of penetration is termed the standard penetration resistance, N-Value.

44 R Froehling & Robertson, Inc. BORING LOG Boring: B-10 (1 of 1) Project No: 66N-0097 Client: Chatham County Project: Chatham County Jail City/State: Pittsboro, North Carolina Elevation Depth Description of Materials (Classification) SURFICIAL ORGANIC SOIL: Brown fine sandy SILT with roots and organics. Stiff, moist, brown sandy SILT (ML). Hard to very hard, moist, tan to light brown fine sandy SILT (ML) with weathered rock fragments. Elevation: 480 ± Total Depth: 18.9' Boring Location: See Boring Location Plan * Sample Blows Sample Depth (feet) N-Value (blows/ft) Drilling Method: 2.25" ID HSA Hammer Type: Automatic Date Drilled: 10/6/11 Driller: J. Gilchrist Remarks GROUNDWATER DATA: IAD: Dry 24 Hrs: Dry Boring terminated at 18.9 feet. 50/5" BORING_LOG 66N-0097 BORING LOGS.GPJ F&R.GDT 11/17/11 *Number of blows required for a 140 lb hammer dropping 30" to drive 2" O.D., 1.375" I.D. sampler a total of 18 inches in three 6" increments. The sum of the second and third increments of penetration is termed the standard penetration resistance, N-Value.

45 R Froehling & Robertson, Inc. BORING LOG Boring: B-11 (1 of 1) Project No: 66N-0097 Client: Chatham County Project: Chatham County Jail City/State: Pittsboro, North Carolina Elevation Depth Description of Materials (Classification) SURFICIAL ORGANIC SOIL: Brown fine sandy SILT with roots and organics. Very stiff, moist, tan to light brown sandy clayey SILT (ML) with weathered rock fragments. PARTIALLY WEATHERED ROCK: Sampled as very hard, tan mixture of sandy SILT and rock fragments. Elevation: 478 ± Total Depth: 18.6' Boring Location: See Boring Location Plan * Sample Blows /5" 43-50/4" Sample Depth (feet) N-Value (blows/ft) Drilling Method: 2.25" ID HSA Hammer Type: Automatic Date Drilled: 10/6/11 Driller: J. Gilchrist Remarks GROUNDWATER DATA: IAD: Dry 24 Hrs: Dry (cave at 7') 28-50/3" 50/4" /4" Boring terminated at 18.6 feet. 50/1" BORING_LOG 66N-0097 BORING LOGS.GPJ F&R.GDT 11/17/11 *Number of blows required for a 140 lb hammer dropping 30" to drive 2" O.D., 1.375" I.D. sampler a total of 18 inches in three 6" increments. The sum of the second and third increments of penetration is termed the standard penetration resistance, N-Value.

46 R Froehling & Robertson, Inc. BORING LOG Boring: B-12 (1 of 1) Project No: 66N-0097 Client: Chatham County Project: Chatham County Jail City/State: Pittsboro, North Carolina Elevation Depth Description of Materials (Classification) SURFICIAL ORGANIC SOIL: Brown fine sandy SILT with roots and organics. Firm, moist, light brown fine sandy SILT (ML) with roots. Very stiff, dry to moist, orangish tan fine sandy SILT (ML) with weathered rock fragments. Very hard, dry, tan silty SAND (SM) with weathered rock fragments. Hard, moist, orangish tan sandy SILT (ML) with weathered rock fragments. Elevation: 480 ± Total Depth: 19.4' Boring Location: See Boring Location Plan * Sample Blows Sample Depth (feet) N-Value (blows/ft) Drilling Method: 2.25" ID HSA Hammer Type: Automatic Date Drilled: 10/6/11 Driller: J. Gilchrist Remarks GROUNDWATER DATA: IAD: Dry 24 Hrs: Dry (cave at 8') PARTIALLY WEATHERED ROCK: Sampled as very hard mixture of sandy SILT and rock fragments. 50/5" Boring terminated at 19.4 feet /5" BORING_LOG 66N-0097 BORING LOGS.GPJ F&R.GDT 11/17/11 *Number of blows required for a 140 lb hammer dropping 30" to drive 2" O.D., 1.375" I.D. sampler a total of 18 inches in three 6" increments. The sum of the second and third increments of penetration is termed the standard penetration resistance, N-Value.

47 R Froehling & Robertson, Inc. BORING LOG Boring: B-13 (1 of 1) Project No: 66N-0097 Client: Chatham County Project: Chatham County Jail City/State: Pittsboro, North Carolina Elevation Depth Description of Materials (Classification) SURFICIAL ORGANIC SOIL: Brown fine sandy SILT with roots and organics. Stiff, moist, orangish brown slightly fine sandy very clayey SILT (MH/CH). Hard to very hard, dry to moist, tan slightly fine sandy clayey SILT (ML/CL) with quartz fragments. Elevation: 486 ± Total Depth: 18.9' Boring Location: See Boring Location Plan * Sample Blows Sample Depth (feet) N-Value (blows/ft) Drilling Method: 2.25" ID HSA Hammer Type: Automatic Date Drilled: 10/9/11 Driller: D. Tignor Remarks GROUNDWATER DATA: IAD: Dry 24 Hrs: Dry (cave at 14') PARTIALLY WEATHERED ROCK: Sampled as very hard sandy SILT and rock fragments. 50/3" 50/5" Hard, wet, tan SILT (ML) with rock fragments PARTIALLY WEATHERED ROCK: Sampled as very hard fine sandy SILT with rock fragments. Boring terminated at 18.9 feet. 50/5" BORING_LOG 66N-0097 BORING LOGS.GPJ F&R.GDT 11/17/11 *Number of blows required for a 140 lb hammer dropping 30" to drive 2" O.D., 1.375" I.D. sampler a total of 18 inches in three 6" increments. The sum of the second and third increments of penetration is termed the standard penetration resistance, N-Value.

48 R Froehling & Robertson, Inc. BORING LOG Boring: B-14 (1 of 1) Project No: 66N-0097 Client: Chatham County Project: Chatham County Jail City/State: Pittsboro, North Carolina Elevation Depth Description of Materials (Classification) SURFICIAL ORGANIC SOIL: Brown fine sandy SILT with roots and organics. Very stiff, moist, orangish brown slightly fine sandy very clayey SILT (MH/CH). Hard to very hard, dry, orangish tan to tan slightly fine sandy clayey SILT (ML/MH). Elevation: 478 ± Total Depth: 18.8' Boring Location: See Boring Location Plan * Sample Blows Sample Depth (feet) N-Value (blows/ft) Drilling Method: 2.25" ID HSA Hammer Type: Automatic Date Drilled: 10/7/11 Driller: D. Tignor Remarks GROUNDWATER DATA: IAD: Dry PARTIALLY WEATHERED ROCK: Sampled as light tan to brown, sandy SILT with rock fragments /5.5" /3" Boring terminated at 18.8 feet. 50/3" BORING_LOG 66N-0097 BORING LOGS.GPJ F&R.GDT 11/17/11 *Number of blows required for a 140 lb hammer dropping 30" to drive 2" O.D., 1.375" I.D. sampler a total of 18 inches in three 6" increments. The sum of the second and third increments of penetration is termed the standard penetration resistance, N-Value.

49 R Froehling & Robertson, Inc. BORING LOG Boring: B-15 (1 of 1) Project No: 66N-0097 Client: Chatham County Project: Chatham County Jail City/State: Pittsboro, North Carolina Elevation Depth Description of Materials (Classification) SURFICIAL ORGANIC SOIL: Brown fine sandy SILT with roots and organics. Stiff, moist, reddish brown slightly fine sandy very clayey SILT (MH/CH). Hard, moist, orangish brown slightly fine sandy clayey SILT (ML/MH). Hard to very hard, dry, tan sandy to very sandy SILT (ML) with rock fragments. Elevation: 483 ± Total Depth: 33.7' Boring Location: See Boring Location Plan * Sample Blows Sample Depth (feet) N-Value (blows/ft) Drilling Method: 2.25" ID HSA Hammer Type: Automatic Date Drilled: 10/6/11 Driller: D. Tignor Remarks GROUNDWATER DATA: IAD: Dry 24 Hrs: 29.3' in PVC Pipe PARTIALLY WEATHERED ROCK: Sampled as very hard sandy SILT and rock fragments /5.5" /2" /3" BORING_LOG 66N-0097 BORING LOGS.GPJ F&R.GDT 11/17/ Boring terminated at 33.7 feet. *Number of blows required for a 140 lb hammer dropping 30" to drive 2" O.D., 1.375" I.D. sampler a total of 18 inches in three 6" increments. The sum of the second and third increments of penetration is termed the standard penetration resistance, N-Value. 50/4" 50/2"

50 R Froehling & Robertson, Inc. BORING LOG Boring: B-16 (1 of 1) Project No: 66N-0097 Client: Chatham County Project: Chatham County Jail City/State: Pittsboro, North Carolina Elevation Depth Description of Materials (Classification) SURFICIAL ORGANIC SOIL: Brown fine sandy SILT with roots and organics. Stiff, moist, reddish brown slightly fine sandy very clayey SILT (MH/CH). Hard to very stiff, moist, orangish tan to tan slightly fine sandy clayey SILT (ML/MH). Elevation: 480 ± Total Depth: 19.4' Boring Location: See Boring Location Plan * Sample Blows Sample Depth (feet) N-Value (blows/ft) Drilling Method: 2.25" ID HSA Hammer Type: Automatic Date Drilled: 10/6/11 Driller: D. Tignor Remarks GROUNDWATER DATA: IAD: Dry 24 Hrs: Dry (cave at 16') Very stiff, wet, light tan silty CLAY (CH/MH) Very hard, moist, light brown sandy SILT (ML) with rock fragments Boring terminated at 19.4 feet /5" BORING_LOG 66N-0097 BORING LOGS.GPJ F&R.GDT 11/17/11 *Number of blows required for a 140 lb hammer dropping 30" to drive 2" O.D., 1.375" I.D. sampler a total of 18 inches in three 6" increments. The sum of the second and third increments of penetration is termed the standard penetration resistance, N-Value.

51 R Froehling & Robertson, Inc. BORING LOG Boring: B-17 (1 of 1) Project No: 66N-0097 Client: Chatham County Project: Chatham County Jail City/State: Pittsboro, North Carolina Elevation Depth Description of Materials (Classification) SURFICIAL ORGANIC SOIL: Brown fine sandy SILT with roots and organics. Firm, moist, reddish brown slightly fine sandy very clayey SILT (MH/CH). Stiff to very stiff, moist, tan slightly fine sandy SILT (ML). Elevation: 477 ± Total Depth: 18.6' Boring Location: See Boring Location Plan * Sample Blows Sample Depth (feet) N-Value (blows/ft) Drilling Method: 2.25" ID HSA Hammer Type: Automatic Date Drilled: 10/5/11 Driller: D. Tignor Remarks GROUNDWATER DATA: IAD: Dry 24 Hrs: Dry PARTIALLY WEATHERED ROCK: Sampled as very hard SILT with weathered rock fragments. Hard, moist, light tan and tan SILT (ML) /5" PARTIALLY WEATHERED ROCK: Sampled as very hard sandy SILT and rock pieces. 50/3" Boring terminated at 18.6 feet. 50/0.5" BORING_LOG 66N-0097 BORING LOGS.GPJ F&R.GDT 11/17/11 *Number of blows required for a 140 lb hammer dropping 30" to drive 2" O.D., 1.375" I.D. sampler a total of 18 inches in three 6" increments. The sum of the second and third increments of penetration is termed the standard penetration resistance, N-Value.

52 R Froehling & Robertson, Inc. BORING LOG Boring: B-18 (1 of 1) Project No: 66N-0097 Client: Chatham County Project: Chatham County Jail City/State: Pittsboro, North Carolina Elevation Depth Description of Materials (Classification) SURFICIAL ORGANIC SOIL: Brown fine sandy SILT with roots and organics. Stiff, moist, reddish brown slightly fine sandy very clayey SILT (MH/CH). with quartz fragments. Very stiff, moist, tan and orangish brown clayey SILT (ML/MH). Elevation: 484 ± Total Depth: 20.0' Boring Location: See Boring Location Plan * Sample Blows Sample Depth (feet) N-Value (blows/ft) Drilling Method: 2.25" ID HSA Hammer Type: Automatic Date Drilled: 10/5/11 Driller: D. Tignor Remarks GROUNDWATER DATA: IAD: Dry 24 Hrs: Dry (cave at 16') Very stiff, moist, light brown slightly fine sandy SILT (ML) Boring terminated at 20.0 feet BORING_LOG 66N-0097 BORING LOGS.GPJ F&R.GDT 11/17/11 *Number of blows required for a 140 lb hammer dropping 30" to drive 2" O.D., 1.375" I.D. sampler a total of 18 inches in three 6" increments. The sum of the second and third increments of penetration is termed the standard penetration resistance, N-Value.

53 R Froehling & Robertson, Inc. BORING LOG Boring: B-19 (1 of 1) Project No: 66N-0097 Client: Chatham County Project: Chatham County Jail City/State: Pittsboro, North Carolina Elevation Depth Description of Materials (Classification) SURFICIAL ORGANIC SOIL: Brown fine sandy SILT with roots and organics. FIrm, moist, reddish brown slightly fine sandy very clayey SILT (MH/CH). Very stiff, moist, reddish brown with black seams, slightly fine sandy clayey SILT (ML/MH). Elevation: 484 ± Total Depth: 20.0' Boring Location: See Boring Location Plan * Sample Blows Sample Depth (feet) N-Value (blows/ft) Drilling Method: 2.25" ID HSA Hammer Type: Automatic Date Drilled: 10/5/11 Driller: D. Tignor Remarks GROUNDWATER DATA: IAD: Dry 24 Hrs: Dry (cave at 16.5') Boring terminated at 20.0 feet BORING_LOG 66N-0097 BORING LOGS.GPJ F&R.GDT 11/17/11 *Number of blows required for a 140 lb hammer dropping 30" to drive 2" O.D., 1.375" I.D. sampler a total of 18 inches in three 6" increments. The sum of the second and third increments of penetration is termed the standard penetration resistance, N-Value.

54 R Froehling & Robertson, Inc. BORING LOG Boring: B-20 (1 of 1) Project No: 66N-0097 Client: Chatham County Project: Chatham County Jail City/State: Pittsboro, North Carolina Elevation Depth Description of Materials (Classification) SURFICIAL ORGANIC SOIL: Brown fine sandy SILT with roots and organics. Stiff, moist, reddish brown slightly fine sandy very clayey SILT (MH/CH). Very stiff, dry to moist, tan slightly sandy clayey SILT (ML/MH) with rock fragments. Very stiff, dry to moist, tan fine sandy SILT (ML). Elevation: 487 ± Total Depth: 20.0' Boring Location: See Boring Location Plan * Sample Blows Sample Depth (feet) N-Value (blows/ft) Drilling Method: 2.25" ID HSA Hammer Type: Automatic Date Drilled: 10/5/11 Driller: D. Tignor Remarks GROUNDWATER DATA: IAD: Dry 24 Hrs: Dry PARTIALLY WEATHERED ROCK: Sampled as very hard SILT with rock fragments. Very hard, moist, tan sandy SILT (ML) */4" Boring terminated at feet BORING_LOG 66N-0097 BORING LOGS.GPJ F&R.GDT 11/17/11 *Number of blows required for a 140 lb hammer dropping 30" to drive 2" O.D., 1.375" I.D. sampler a total of 18 inches in three 6" increments. The sum of the second and third increments of penetration is termed the standard penetration resistance, N-Value.

55 APPENDIX III LABORATORY TEST RESULTS Chatham County Chatham County Jail F&R Project No. 66N-0097 November 16, 2011

56 R Froehling & Robertson, Inc. ATTERBERG LIMITS Project No:66N-0097 Client:Chatham County Project:Chatham County Jail City/State:Pittsboro, North Carolina CL CH Plasticity Index CL-ML ML MH Liquid Limit US_ATTERBERG_LIMITS 66N-0097 BORING LOGS.GPJ F&R.GDT 11/3/11 Boring No. B-1 B-16 B-19 B-2 B-4 B-6 Depth LL PL PI Fines Classification % Natural Water Content Brown, ELASTIC SILT (MH) Orange-Brown, FAT CLAY (CH) Brown, ELASTIC SILT (MH) Orange-Brown, ELASTIC SILT (MH) Tan-White, LEAN CLAY with SAND (CL) Orange-Brown, ELASTIC SILT (MH) 16.9

57 FROEHLING & ROBERTSON % Passing the #200 Project: Chatam County Jail Project No: 66N-0097 Client: Chatam County Jail Date: 10/25/ Boring No. B-1 B-2 B-4 B-6 B-16 B-19 B-2 B-26 Depth (ft.) Pan # K-01 S-04 1 Wet soil + tare (g) Dry soil + tare (g) Wt. of Water (g) Tare wt. (g) Dry wt. of Soil (g) Dry wt. + tare Soil after wash Dry wt. of soil after wash Wt. of -#200 Material % Passing # Moisture %

58

59 COMPACTION TEST REPORT DATE: 10/21/2011 PROJECT NO.: 66N-0097 PROJECT: Chatam County Jail Test specification: ASTM D Method A Standard 100% SATURATION CURVES FOR SPEC. GRAV. EQUAL TO: Dry density, pcf Water content, % No. LOCATION AND DESCRIPTION REMARKS 01 Location: Boring B-20 Depth: 0' - 5' Sample Number: 01 Sample was Received on 10/14/2011 Light Orange, Elastic Silt. No. USCS LL PI NAT. MOIST. OVERSIZE %< No.200 MAX. DRY DEN. OPT. MOIST. 01 MH %>#4= % % FROEHLING & ROBERTSON, INC. Figure 01 Tested By: J.Pope Checked By: D.Jenks

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63 APPENDIX IV ASFE DOCUMENT Chatham County Chatham County Jail F&R Project No. 66N-0097 November 16, 2011

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66 FROEHLING & ROBERTSON, INC. SUBSURFACE INVESTIGATION REPORT Chatham County Jail Off Site Sewer Force Main, Gravity Sewer and Water Line Pittsboro, NC F&R Project No. 66P 0090 Prepared for: Chatham County Public Works P.O. Box 910 Pittsboro, North Carolina September 7, Hubert Street Raleigh, North Carolina

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68 TABLE OF CONTENTS PAGE 1.0 PURPOSE AND SCOPE OF SERVICES PROJECT INFORMATION EXPLORATION PROCEDURES Field Exploration Laboratory Testing REGIONAL GEOLOGY SUBSURFACE CONDITIONS General Surficial Materials Fill/Possible Fill Soils Residual Soils Partially Weathered Rock & Auger Refusal Soil Moisture & Groundwater Conditions LIMITATIONS...7 APPENDIX I Key to Soil Classification Unified Soil Classification Chart Boring Logs APPENDIX II ASFE Document: Important Information about your Geotechnical Engineering Report

69 1.0 PURPOSE AND SCOPE OF SERVICES The purpose of the subsurface investigation was to explore the subsurface conditions at the site with respect to the installation of sewer and water utility lines. The information obtained will be used for contractor bidding purposes primarily as it relates to boring and jacking or directional drilling methods anticipated to be required at stream crossings. F&R s scope of services included the following: Advancing 11 borings (B 1 through B 11) within the area of the 4 sewer force main to depths ranging from 8 to 15 feet; Advancing 3 borings (B 14 through B 16) within the area of the 8 gravity sewer line to depths ranging from 7.5 to 18.5 feet. Note that borings B 12 and B 13, which were located in this area, were not performed due to property access issues; Advancing 2 borings (B 17 & B 18) within the area of the 8 water main to depths of 14.3 and 17 feet, respectively; Preparing typed Borelog Reports; Preparing this report by professional engineers. This report is organized to discuss Project Information (Section 2.0), Exploration Procedures (Section 3.0), Regional Geology (Section 4.0), and Subsurface Conditions (Section 5.0). 2.0 PROJECT INFORMATION The proposed utility lines begin at the proposed Chatham County Jail site, which is located on Landfill Road off of US Highway 64 in Pittsboro, North Carolina. More specifically, the water main runs along the north side of the jail and then south along East Alston Road for a total length of approximately 1.3 miles. The sewer force main begins at the jail and extends southward along the east side of Landfill Road and then eastward along the south side of US Highway 64 for a total length of approximately 4.5 miles. The sewer force main then transitions to a gravity sewer for a distance of approximately 0.5 miles, and terminates at the Pittsboro city limits. Chatham County Public Works 1 Chatham County Jail Sewer & Water Lines F&R Project No. 66P 0090 September 7, 2012

70 3.0 EXPLORATION PROCEDURES 3.1 FIELD EXPLORATION A subsurface exploration was conducted by F&R in August of 2012 during which F&R performed a total of 16 borings (B 1 through B 11 & B 14 through B 18). Borings B 12 and B 13 were unable to be performed due to the inability to access the adjacent private property where the proposed borings were located. Borings B 1 through B 11 were located along the proposed sewer force main; borings B 14 through B 16 were located along the proposed gravity sewer; and borings B 17 and B 18 were located along the proposed water main. The borings were advanced to depths ranging from approximately 7.5 to 18.5 feet below the existing ground surface. The borings were located in the field by F&R at locations that were reasonably accessible to our drilling equipment and clear of overhead and underground utilities. After the completion of drilling, the final northing and easting coordinates and boring collar elevations were then provided by the project surveyor Riley Surveying, PA. The coordinates are indicated on the respective boring logs, and the boring locations will be shown on plans prepared by Landworks Design Group, P.A. The borings were performed by two F&R drill crews using CME 55 ATV mounted and CME 55 Track mounted drill rigs utilizing 2 1/4 inside diameter (I.D.) hollow stem augers for borehole stabilization. Representative soil samples were obtained using a standard two inch outside diameter (O.D.) split barrel sampler in general accordance with ASTM D 1586, Penetration Test and Split Barrel Sampling of Soils (Standard Penetration Test). The number of blows required to drive the split barrel sampler three consecutive 6 inch increments with an automatic hammer is recorded and the blows of the last two 6 inch increments are added to obtain the Standard Penetration Test (SPT) N values representing the penetration resistance of the soil. Standard Penetration Tests were performed almost continuously to a depth of 10 feet and at a nominal interval of approximately 5 feet thereafter. An automatic hammer was used to perform the Standard Penetration Test (SPT) on this project. Research has shown that the Standard Penetration Resistance (N value) determined by an Chatham County Public Works 2 Chatham County Jail Sewer & Water Lines F&R Project No. 66P 0090 September 7, 2012

71 automatic hammer is different than the N value determined by the safety hammer method. Most correlations that are published in technical literature are based on the N value determined by the safety hammer method. This is commonly termed N 60 as the rope and cathead with a safety hammer delivers about 60 percent of the theoretical energy delivered by a 140 pound hammer falling 30 inches. Several researchers have proposed correction factors for the use of hammers other than the safety hammer to correct the values to be equivalent to the safety hammer SPT N 60 values. The correction is made using the following equation: N 60 = N field x C E N field is the value recorded in the field and C E is the drill rod energy ratio for the hammer utilized in the field. When using an automatic hammer, it is recommended that a correction factor (C E ) of 1.3 be utilized to covert N field values to N 60 values in accordance with guidelines provided in the Performance and Use of the Standard Penetration Test in Geotechnical Engineering Practice manual published by the Center for Geotechnical Practice and Research at the Virginia Polytechnical Institute and State University. The N values reported on the Boring Logs included in this report are the actual, uncorrected, field derived values (N field ). corrected N 60 values be used for engineering analysis. It is recommended that Representative soil samples were sealed in glass jars, labeled and transported to our laboratory for classification by a geotechnical engineer. The soil samples were visually classified in general accordance with the Unified Soil Classification System (USCS), using visual manual identification procedures (ASTM D 2488). The Boring Log for each test boring is presented in Appendix I of this report. Groundwater levels were recorded in the borings immediately after drilling activities were completed. 3.2 LABORATORY TESTING Laboratory testing was not a part of our scope of work for this project. Chatham County Public Works 3 Chatham County Jail Sewer & Water Lines F&R Project No. 66P 0090 September 7, 2012

72 4.0 REGIONAL GEOLOGY The project site is located in the Carolina Slate Belt of the Piedmont Geologic Province of North Carolina. This area generally consists of hills and ridges that are intertwined with an established system of draws and streams. According to the North Carolina Geologic Map (1985), the bedrock found in this area is primarily mapped as Felsic and Mafic Metavolcanic Rock. The virgin soils of the Piedmont are the residual product of in place chemical weathering of rock that was similar to the rock presently underlying the site. In areas not altered by erosion or disturbed by the activities of man, the typical residual soil profile consists of clayey soils near the surface, where soil weathering is more advanced, underlain by silts and sandy silts above weathered rock and crystalline rock. The boundary between soil and rock is typically not sharply defined and a transitional zone termed Weathered Rock is typically found overlying the more competent bedrock. Weathered Rock (WR) is defined, for engineering purposes, as residual material exhibiting Standard Penetration Test (SPT) resistances in excess of 100 blows per foot (bpf). Weathering is facilitated by fractures, joints and by the presence of less resistant rock types. Consequently, the profile of residual soil, partially weathered rock, and rock can be irregular and erratic, even over short horizontal distances. 5.0 SUBSURFACE CONDITIONS 5.1 GENERAL The subsurface conditions discussed in the following sections of this report and those shown on the attached Boring Logs represent an estimate of the subsurface conditions based on interpretation of the boring data using normally accepted geotechnical engineering judgments. The transitions between different soil strata are usually less distinct than those shown on the Boring Logs. Sometimes the relatively small sample obtained in the field is insufficient to definitively describe the origin of the subsurface material. Although individual soil test borings are representative of the subsurface conditions at the boring locations on the dates shown, they are not necessarily indicative of subsurface conditions at other locations or at other times. Chatham County Public Works 4 Chatham County Jail Sewer & Water Lines F&R Project No. 66P 0090 September 7, 2012

73 Data from the specific soil test borings are shown on the attached Boring Logs presented in Appendix I of this report. 5.2 SURFICIAL MATERIALS Surficial Organic Soils were encountered in all of the test borings except borings B 8 and B 15 and extended from the ground surface to depths of approximately 0.1 to 0.4 feet. The Surficial Organic Soils generally consisted of brown and black fine sandy silt and silty fine sand with roots, fibrous matter, and/or other organic materials. In some of the borings, roots were encountered below the Surficial Organic Soil extending to depths of approximately 2 feet. Surficial Organic Soil is generally unsuitable for engineering purposes. F&R has not performed any laboratory testing to determine the organic content or other horticultural properties of the observed Surficial Organic Soil materials. Therefore, the term Surficial Organic Soil is not intended to indicate suitability for landscaping and/or other purposes. The Surficial Organic Soil depths provided in this report are based on driller observations and should be considered approximate. We note that the transition from Surficial Organic Soil to underlying materials may be gradual, and therefore the observation and measurement of Surficial Organic Soil depths is subjective. Actual Surficial Organic Soil depths should be expected to vary. 5.3 FILL/POSSIBLE FILL SOILS Existing fill/possible fill soil was encountered below the Surficial Organic Soils in all borings except B 1, B 2 and B 9 and generally consisted of sandy silt, sandy clay and/or silty clay (USCS classification ML, CL & CH) with varying amounts of gravel and organics. The SPT N values in the fill ranged from 3 to 23 blows per foot (bpf), which is indicative of poorly compacted (typically 0 to 4 bpf) to well compacted (typically 8 bpf and higher) soils. However, most of the fill encountered appears moderately (typically 5 to 7 bpf) to well compacted. The fill/possible fill was present to depths ranging from 1 to 8.5 feet. In boring B 4, the fill consisted of silty sand with boulders and rip rap to a depth of approximately 4 feet. The SPT N values in this zone were over 100 bpf; however, this is not an Chatham County Public Works 5 Chatham County Jail Sewer & Water Lines F&R Project No. 66P 0090 September 7, 2012

74 accurate indicator of the compaction of the soils due to the presence of the boulders and riprap. 5.4 RESIDUAL SOILS Native/residual soils were encountered below the Surficial Organic Soils in borings B 1, B 2 and B 9, and below the fill soils in borings B 3, B 6 through B 8, B 10, B 11, and B 14 through B 18. No residual soils were encountered in borings B 4 and B 5. The residual soils generally consisted of variations of low to high plasticity clays and silts with varying amounts of gravel/rock fragments, fine sand and coarse sand (USCS ML, CL & CH). SPT N values obtained in these soils ranged from 5 to 86 bpf although a majority ranged from 11 to 25 bpf indicating consistencies of stiff to very stiff. Soft soils (i.e., soils with N values of 4 bpf or less) were not encountered in any of the borings. Highly plastic silty clays (USCS CH) were encountered in borings B 2, B 17 and B 18 from depths of 0.4 to 1.5 feet, 8.5 to 13.5 feet, and 12 to 16 feet, respectively. The consistency of the highly plastic soils typically ranged from medium stiff to very stiff. 5.5 PARTIALLY WEATHERED ROCK & AUGER REFUSAL Partially Weathered Rock (PWR) and Rock was encountered in all of the borings except borings B 3 and B 16. The PWR was sampled as very hard sandy silt and very dense silty sand with rock fragments. The depth to PWR varied from as shallow as 4 to 4.5 feet in borings B 2, B 4, B 8 and B 9 to as deep as 13.5 to 16 feet in borings B 7, B 15, B 17 and B 18. The PWR typically extended from these depths to boring termination. However, in boring B 2, a layer of dense silty sand was encountered within the PWR. The SPT N values in the PWR ranged from 50/0 to 50/6. Auger refusal was encountered in borings B 1, B 4, B 5, B 8, B 10, B 11, B 14, B 17 and B 18 at depths ranging from 7.5 to 14.3 feet. Auger refusal is a designation applied to any material that cannot be penetrated by the soil auger, and is typically caused by encountering boulders, hard rock lenses/ledges or bedrock. The nature of auger refusal was not explored in these borings, but is anticipated to represent the bedrock surface. Chatham County Public Works 6 Chatham County Jail Sewer & Water Lines F&R Project No. 66P 0090 September 7, 2012

75 5.6 SOIL MOISTURE & GROUNDWATER CONDITIONS In general, the recovered soil samples were dry to moist extending from the ground surface to boring termination. Wet soils were only encountered in borings B 4 from 4 to 10.4 feet, B 16 from 0.3 to 3.5 feet, and B 17 from 6 to 8.5 feet. The water level was measured immediately after drilling in all of the borings. Typically, no groundwater was encountered except at borings B 4, B 5 and B 16, which encountered water at depths of 7, 7, and 13.5 feet below the existing ground surface, respectively. It should be noted that groundwater elevations vary depending upon seasonal factors such as precipitation and temperature. As such, soil moisture and groundwater conditions at other times of the year may vary from those observed at the time of this exploration and described in this report. 6.0 LIMITATIONS This report has been prepared for the exclusive use of Chatham County Public Works and their agents for specific application to the referenced site in accordance with generally accepted soil and foundation subsurface exploration practices. No other warranty, expressed or implied, is made. These findings presented do not reflect variations in subsurface conditions that could exist intermediate of the boring locations or in unexplored areas of the site. Should such variations become apparent during construction, we reserve the right to re evaluate our findings based upon on site observations of the conditions. F&R was not requested to provide any geotechnical engineering analyses or recommendations on this project. Chatham County Public Works 7 Chatham County Jail Sewer & Water Lines F&R Project No. 66P 0090 September 7, 2012

76 APPENDIX I KEY TO SOIL CLASSIFICATION UNIFIED SOIL CLASSIFICATION CHART BORING LOGS

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97 APPENDIX II ASFE DOCUMENT

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100 HQ: 3015 DUMBARTON ROAD RICHMOND, VIRGINIA T F VIRGINIA NORTH CAROLINA SOUTH CAROLINA MARYLAND DISTRICT OF COLUMBIA A Minority Owned Company