Geotechnical Engineering Report

Transcription

1

2

3 Geotechnical Engineering Report Union County Landfill Retaining Wall Wingate, North Carolina October 22, 2015 Project No Prepared for: CDM Smith Charlotte, North Carolina Prepared by: Terracon Consultants, Inc. Charlotte, North Carolina

4

5 TABLE OF CONTENTS Page EXECUTIVE SUMMARY... i 1.0 INTRODUCTION PROJECT INFORMATION Project Description Site Location and Description SUBSURFACE CONDITIONS Geology Typical Profile Groundwater RECOMMENDATIONS FOR DESIGN AND CONSTRUCTION Geotechnical Considerations Earthwork Site Preparation Compaction Requirements Grading and Drainage Earthwork Construction Considerations Excavations Foundations Foundation Design Recommendations Foundation Construction Considerations Lateral Earth Pressures Global Slope Stability GENERAL COMMENTS APPENDIX A FIELD EXPLORATION Exhibits A-1a & A-1b Site Location Map Exhibit A-2 Boring Location Plan Exhibit A-3 Field Exploration Description Exhibits A-4 to A-7 Boring Logs APPENDIX B SUPPORTING INFORMATION Exhibits B-1 Laboratory Testing APPENDIX C SUPPORTING DOCUMENTS Exhibit C-1 General Notes Exhibit C-2 Unified Soil Classification System APPENDIX D SLOPE STABILITY ANALYSIS Exhibit D-1 Slope Stability Section Plan Exhibit D-2 Slope Stability Section A-A Responsive Resourceful Reliable

6 Geotechnical Engineering Report Union County Landfill Retaining Wall Wingate, North Carolina October 22, 2015 Terracon Project No EXECUTIVE SUMMARY A geotechnical investigation has been performed for the proposed retaining wall, located at the Union County Landfill in Wingate, North Carolina. Four (4) borings, designated B-1 through B-4 were performed to depths of approximately 15 to 28 feet below the existing ground surface in the proposed retaining wall area. Based on the information obtained from our subsurface exploration, the site can be developed for the proposed project. The following geotechnical considerations were identified: The residual soils and PWR as encountered in our borings at the site appear suitable to support the proposed retaining wall on shallow foundations provided the subgrade is prepared as outlined in this report. The proposed retaining wall may be supported on conventional strip footings with a net allowable bearing pressure of 3,000 psf for footings in residual soil. If footings are bearing on or extended further below existing grades to PWR, a higher bearing pressure of 6,000 psf may be used. Total and differential settlements of less than 1 inch and less than ½ inch over 40 feet or less are anticipated at these bearing pressures. Further details and recommendations are provided herein. The residual soils encountered at the boring locations may be excavated with conventional construction equipment, such as bulldozers, backhoes, and trackhoes. However, difficult excavation of very stiff to hard residual soils and partially weathered rock (PWR) may be encountered. We have performed a slope stability analysis at the critical section of the proposed retaining wall alignment. Based on our analysis, the section satisfies the minimum factor of safety. Additional details are included herein. There are two culverts on-site that drain into the vicinity of the proposed retaining wall. These culverts may impact design and should be accounted for by the engineer or addressed during construction. This summary should be used in conjunction with the entire report for design purposes. It should be recognized that details were not included or fully developed in this section, and the report must be read in its entirety for a comprehensive understanding of the items contained herein. The section titled GENERAL COMMENTS should be read for an understanding of the report limitations. Responsive Resourceful Reliable i

7 GEOTECHNICAL ENGINEERING REPORT UNION COUNTY LANDFILL RETAINING WALL WINGATE, NORTH CAROLINA Project No October 22, INTRODUCTION A geotechnical engineering report has been completed for the proposed retaining wall, located at the Union County Landfill in Wingate, North Carolina. Four (4) borings, designated B-1 through B-4 were performed to depths of approximately 15 to 28 feet below the existing ground surface in the proposed retaining wall area. Logs of the borings and a description of the field exploration, along with a Site Location Map and Boring Location Plan are included in Appendix A of this report. The purpose of these services is to provide information and geotechnical engineering recommendations relative to: subsurface soil conditions foundation design and construction groundwater conditions lateral earth pressures earthwork and excavations global slope stability 2.0 PROJECT INFORMATION 2.1 Project Description ITEM Structures Surcharge loads (assumed) General Site Grading Cut and fill slopes Free-standing retaining walls Below Grade Areas DESCRIPTION New concrete retaining wall and asphalt pavement. Traffic: 300 psf Not provided, but anticipated to be close to existing grades. None anticipated. Temporary slopes anticipated to be maximum 3:1 (Horizontal to Vertical). Concrete retaining wall. Wall estimated to be 9.3 feet high and approximately 170-feet long. None anticipated. 2.2 Site Location and Description Location ITEM DESCRIPTION This project is located at the Union County Landfill located at 2125 Austin Chaney Road in Wingate, NC. Responsive Resourceful Reliable 1

8 Geotechnical Engineering Report Union County Landfill Retaining Wall Wingate, North Carolina October 22, 2015 Terracon Project No ITEM Existing development Current ground cover Existing topography DESCRIPTION The property includes an existing parking area, multiple buildings, and waste disposal areas adjacent to an existing retaining wall. Manicured grass areas, trees, and asphalt parking and drive areas. The site is relatively flat in the vicinity of the asphalt parking and access drive areas. The site appears to slope down approximately 8-feet for the waste disposal containers adjacent to the existing retaining wall. 3.0 SUBSURFACE CONDITIONS 3.1 Geology The project site is located in the Piedmont Physiographic Province, an area underlain by ancient igneous and metamorphic rocks. The residual soils in this area are the product of in-place chemical weathering of rock. The typical residual soil profile consists of clayey soils near the surface where soil weathering is more advanced, underlain by sandy silts and silty sands that generally become harder with depth to the top of parent bedrock. Alluvial soils are typically present within floodplain areas along creeks and rivers in the Piedmont. According to the 1985 Geologic Map of North Carolina, the site is within the Carolina Slate Belt. The bedrock underlying the site generally consists of Cid Formation Metamudstone and Meta-Argillite, which is described as thin to thick bedded; bedding plane and axial-planar cleavage common; interbedded with metasandstone, metaconglomerate, and metavolcanic rock. The boundary between soil and rock in the Piedmont is not sharply defined. A transitional zone termed partially weathered rock is normally found overlying the parent bedrock. Partially weathered rock is defined for engineering purposes as residual material with a standard penetration test resistance exceeding 100 blows per foot. The transition between hard/dense residual soils and partially weathered rock occurs at irregular depths due to variations in degree of weathering. Groundwater is typically present in fractures within the partially weathered rock or underlying bedrock in upland areas of the Piedmont. Fluctuations in groundwater levels on the order of 2 to 4 feet are typical in residual soils and partially weathered rock in the Piedmont, depending on variations in precipitation, evaporation, and surface water runoff. Seasonal high groundwater levels are expected to occur during or just after the typically cooler months of the year (November through April). 3.2 Typical Profile Based on the results of the borings, subsurface conditions on the project site can be generalized as follows: Responsive Resourceful Reliable 2

9 Geotechnical Engineering Report Union County Landfill Retaining Wall Wingate, North Carolina October 22, 2015 Terracon Project No Surficial materials encountered in the borings included approximately 3 to 5 inches of topsoil or stone. Below the surficial materials, residual soils were encountered in each of our borings, except B-4, to depths ranging from approximately 3 to 5.5 feet below existing grades. Residual soils encountered consisted of sandy silt. This soil visually classifies as ML in accordance with the Unified Soil Classification System (USCS). Standard penetration test values (N-values) in the sandy silt ranged from 29 to 73 blows per foot (bpf), indicating a very stiff to hard consistency. Partially weathered rock (PWR) was encountered in borings B-1 to B-3 below the residual soils, and below the surficial materials in boring B-4. The PWR was sampled and visually classified as sandy silt. Auger refusal was encountered in each boring at depths ranging from approximately 15 to 28 feet below existing grades. Conditions encountered at each boring location are indicated on the individual boring logs. Stratification boundaries on the boring logs represent the approximate location of changes in soil types; in-situ, the transition between materials may be gradual. Details for each of the borings can be found on the boring logs in Appendix A of this report. 3.3 Groundwater The boreholes were observed during and after completion of drilling for the presence and level of groundwater. Groundwater was not encountered in any of the borings. Each borehole was immediately backfilled after drilling, making subsequent groundwater measurements unobtainable. It should be recognized that fluctuations of the groundwater table will occur due to seasonal variations in the amount of rainfall, runoff and other factors not evident at the time the borings were performed. Therefore, groundwater levels during construction or at other times in the life of the structure may be higher or lower than the levels indicated on the boring logs. The possibility of groundwater level fluctuations should be considered when developing the design and construction plans for the project. 4.0 RECOMMENDATIONS FOR DESIGN AND CONSTRUCTION 4.1 Geotechnical Considerations In our opinion, the residual soils and PWR as encountered in our borings at the site are suitable to support the proposed retaining wall on shallow foundations provided the subgrade is prepared as outlined in this report. We recommend close examination of the bearing materials be performed during construction to confirm stable soil conditions. Responsive Resourceful Reliable 3

10 Geotechnical Engineering Report Union County Landfill Retaining Wall Wingate, North Carolina October 22, 2015 Terracon Project No The residual soils encountered at the boring locations may be excavated with conventional construction equipment, such as bulldozers, backhoes, and trackhoes. However, difficult excavation of very stiff to hard residual soils and partially weathered rock (PWR) may be encountered. We recommend that the contractor submit unit rates for difficult excavations in their bid. Additional information regarding difficult excavation is included herein. Based on the results of our subsurface exploration, it is our opinion that the proposed retaining wall may be supported on conventional strip footings with net allowable bearing pressures of 3,000 psf in residual soils. If footings are bearing on or extended further below existing grades to PWR, a higher bearing pressure of 6,000 psf may be used. Total and differential settlements of less than 1 inch and less than ½ inch over 40 feet or less are anticipated at these bearing pressures, if subgrade soils are prepared as described in this report. Further details and recommendations are provided herein. The proposed site retaining wall was evaluated for global slope stability. The slope stability analysis was performed at a critical section of the proposed retaining wall alignment. Based on our analysis, the section satisfies the minimum factor of safety. Additional details are included herein. It should be noted that during site drilling operations, it was observed that there are two culverts that drain into the vicinity of the proposed retaining wall. While not part of our scope of services, these culverts may impact design and should be accounted for by the engineer or addressed during construction. 4.2 Earthwork Site Preparation Existing vegetation, topsoil and any otherwise unsuitable material should be removed from the construction areas prior to placing fill. Existing utilities should be removed and relocated, or abandoned in place and filled with concrete or grout. The exposed subgrade soils in areas to receive fill or at the subgrade elevation in cut areas should be proofrolled to detect soft or loose soils and other unsuitable materials that may be present. Proofrolling should be performed with a moderately loaded, tandem axle dump truck or similar pneumatic-tired construction equipment weighing approximately 10 to 15 tons in the proposed building areas. A Terracon representative should observe this operation to aid in delineating unstable soil areas. Proofrolling should be performed after a suitable period of dry weather to avoid degrading an otherwise acceptable subgrade. Soils which continue to rut or deflect excessively under the proofrolling operations should be remediated as recommended by the geotechnical engineer. If subgrade soils are unsuitable, they will require removal and replacement; however, if they are unstable due to excessive moisture, the most economical solution for remediation may be to scarify, dry and recompact the material. This remediation is most effective during the typically hotter months of the year (May to October). If construction is performed during the cooler period Responsive Resourceful Reliable 4

11 Geotechnical Engineering Report Union County Landfill Retaining Wall Wingate, North Carolina October 22, 2015 Terracon Project No of the year, the timeline for scarifying, drying, and recompacting typically increases considerably and may lead to alternative remediation solutions. These solutions can include overexcavation of some or all of the unstable material to be backfilled with either approved engineered fill or ABC Stone. Potential undercutting can be reduced if the site preparation work is performed during a period of dry weather and if construction traffic is kept to a minimum on prepared subgrades. We recommend that the contractor submit a unit rate cost for undercutting as part of the bidding process. The existing soils encountered in our borings appear to be suitable for re-use as engineered fill. Engineered fill should meet the following material property requirements: Fill Type 1 USCS Classification Acceptable Location for Placement On-site Soils ML (LL < 50 & PI < 30) All locations and elevations Imported Low-Plasticity Soils ML, CL, SC, SM (LL < 50 & PI < 20 with a minimum 15% passing No. 200 sieve) All locations and elevations 1. Controlled, compacted fill should consist of approved materials that are free of organic matter and debris. Frozen material should not be used, and fill should not be placed on a frozen subgrade. A sample of each material type should be submitted to the geotechnical engineer for evaluation Compaction Requirements We recommend that engineered fill be tested for moisture content and compaction during placement. Should the results of the in-place density tests indicate the specified moisture or compaction limits have not been met, the area represented by the test should be reworked and retested as required until the specified moisture and compaction requirements are achieved. Engineered fill should meet the following compaction requirements: ITEM DESCRIPTION Fill Lift Thickness 8 to 10 inches or less in loose thickness when heavy, self-propelled compaction equipment is used 4 to 6 inches in loose thickness when handguided equipment (e.g. jumping jack or plate compactor) is used Responsive Resourceful Reliable 5

12 Geotechnical Engineering Report Union County Landfill Retaining Wall Wingate, North Carolina October 22, 2015 Terracon Project No ITEM Minimum Compaction Requirements Moisture Content Requirements DESCRIPTION 95% of the materials maximum standard Proctor dry density (ASTM D 698) The upper 12 inches in pavement and building areas should be compacted to at least 100% of the materials maximum standard Proctor dry density (ASTM D 698) Within 3% of the optimum moisture content value as determined by the standard Proctor test at the time of placement and compaction Grading and Drainage Final surrounding grades should be sloped away from the retaining wall on all sides to prevent ponding of water. It should be noted that during site drilling operations, it was observed that there are two culverts that drain into the vicinity of the proposed retaining wall. While not part of our scope of services, these culverts may impact design and should be accounted for by the engineer or addressed during construction Earthwork Construction Considerations Unstable subgrade conditions could develop during general construction operations, particularly if the soils are wetted and/or subjected to repetitive construction traffic. The use of light construction equipment would aid in reducing subgrade disturbance. Should unstable subgrade conditions develop, stabilization measures will need to be employed. Upon completion of filling and grading, care should be taken to maintain the subgrade moisture content prior to construction of on-grade slab and pavements. Construction traffic over the completed subgrade should be avoided to the extent practical. The site should also be graded to prevent ponding of surface water on the prepared subgrades or in excavations. If the subgrade should become frozen, desiccated, saturated, or disturbed, the affected material should be removed or these materials should be scarified, moisture conditioned, and recompacted prior to on-grade slab and pavement construction. The geotechnical engineer should be retained during the construction phase of the project to observe earthwork and to perform necessary tests and observations during subgrade preparation and just prior to construction of building slabs and pavements Excavations The residual and fill soils encountered at the boring locations may be excavated with conventional construction equipment, such as bulldozers, backhoes, and trackhoes; however, very dense/hard residual soils and PWR were encountered at relatively shallow depths in each of the borings. Additionally, auger refusal was encountered in each of the borings at depths Responsive Resourceful Reliable 6

13 Geotechnical Engineering Report Union County Landfill Retaining Wall Wingate, North Carolina October 22, 2015 Terracon Project No ranging from approximately 15 to 28 feet below existing grades. Shallow PWR and bedrock material may also be encountered between boring locations. Smaller equipment may have difficulty excavating PWR. A larger trackhoe or bulldozer equipped with a single-tooth ripper may be required to excavate these materials. Some PWR, especially in confined excavations, and rock will require blasting or impact hammering to efficiently excavate. We recommend that unit rates for mass rock and trench rock be included in the bid package to limit disputes, in the case that rock-like materials are encountered. PWR may be encountered during site development. The depth and thickness of PWR, boulders, and rock lenses or seams can vary dramatically in short distances and between the testing locations. It is our opinion that a clear and appropriate definition of rock be included in the project specifications to reduce the potential for misunderstandings. A sample definition of rock for excavation specifications is provided below: Mass Rock is defined as any material that cannot be dislodged by a Caterpillar D-8 Bulldozer, or equivalent, equipped with a single tooth ripper, without the use of impact hammers or drilling and blasting. Trench Rock is defined as any material that cannot be dislodged by a Caterpillar 312 hydraulic backhoe, or equivalent, without the use of impact hammers or drilling and blasting. Boulders or masses of rock exceeding ½ or ¼ cubic yard in volume shall also be considered mass or trench rock, respectively, during excavation. These classifications do not include materials such as loose rock, concrete, or other materials that can be removed by means other than impact hammering, but which for any reason, such as economic reasons, the Contractor chooses to remove by impact hammering. As a minimum, all temporary excavations should be sloped or braced as required by Occupational Safety and Health Administration (OSHA) regulations to provide stability and safe working conditions. Temporary excavations may be required during grading operations. The grading contractor should be responsible for designing and constructing stable, temporary excavations and should shore, slope or bench the sides of the excavations as required, to maintain stability of both the excavation sides and bottom. All excavations should comply with applicable local, state and federal safety regulations, including the current OSHA Excavation and Trench Safety Standards. Construction site safety is the sole responsibility of the contractor who controls the means, methods and sequencing of construction operations. Under no circumstances shall the information provided herein be interpreted to mean that Terracon is assuming any responsibility Responsive Resourceful Reliable 7

14 Geotechnical Engineering Report Union County Landfill Retaining Wall Wingate, North Carolina October 22, 2015 Terracon Project No for construction site safety or the contractor's activities; such responsibility shall neither be implied nor inferred. 4.3 Foundations In our opinion, the proposed retaining wall can be supported by shallow, strip footing foundation systems bearing within suitable residual soils and PWR or new properly compacted fill. Design recommendations for shallow foundations for the proposed structure are presented in the following sections Foundation Design Recommendations DESCRIPTION Net allowable bearing pressure 1 Minimum dimensions Minimum embedment below finished grade Approximate total settlement Approximate differential settlement Wall 3,000 psf (residual soil) / 6,000 psf (PWR) 24 inches 18 inches < 1 inch < 1/2 inch over 40 feet 1. The recommended net allowable bearing pressure is the pressure in excess of the minimum surrounding overburden pressure at the footing base elevation. Assumes any fill or soft soils, if encountered, will be undercut and replaced with engineered fill Foundation Construction Considerations The foundation bearing materials should be evaluated at the time of the foundation excavation. A representative of Terracon should use a combination of hand auger borings and dynamic cone penetrometer (DCP) testing in conjunction with visual observations to determine the suitability of the bearing materials for the design bearing pressure. The base of all foundation excavations should be free of water and loose soil and rock prior to placing concrete. Concrete should be placed soon after excavating to reduce bearing soil disturbance. Should the soils at bearing level become disturbed, saturated, or frozen, the affected soil should be removed prior to placing concrete. Exposure to inclement weather can introduce unwanted moisture into the footing subgrade. If construction occurs during inclement weather, and concreting of foundations is not possible at the time they are excavated, a layer of lean concrete should be placed on exposed bearing surfaces for protection. Where high moisture conditions are encountered at footing bearing elevations, the bottom of the excavations could be stabilized with a relatively clean, well-graded crushed stone or gravel, or a lean concrete mud mat to provide a working base for construction. If unsuitable bearing soils are encountered in footing excavations, the excavations should be extended deeper to suitable soils. The footings could bear directly on the soils at the lower level Responsive Resourceful Reliable 8

15 Geotechnical Engineering Report Union County Landfill Retaining Wall Wingate, North Carolina October 22, 2015 Terracon Project No or on lean concrete backfill placed in the excavations. The footings could also bear on properly compacted structural fill extending down to the suitable soils. Overexcavation for compacted structural fill placement below footings should extend laterally beyond all edges of the footings at least 8 inches per foot of overexcavation depth below footing base elevation. The overexcavation should then be backfilled up to the footing base elevation with well-graded granular material placed in lifts of 10 inches or less in loose thickness and compacted to at least 98 percent of the material's maximum standard Proctor dry density (ASTM D-698). The overexcavation and backfill procedures are described in the following figure. D = Depth of overexcavation to suitable soils, as determined by a Terracon representative during construction. 4.4 Lateral Earth Pressures Reinforced concrete walls with unbalanced backfill levels on opposite sides should be designed for earth pressures at least equal to those indicated in the following table. Earth pressures will be influenced by structural design of the walls, conditions of wall restraint, methods of construction and/or compaction and the strength of the materials being restrained. Two wall restraint conditions are shown. Active earth pressure is commonly used for design of free-standing cantilever retaining walls and assumes wall movement. The "at-rest" condition assumes no wall movement. The recommended design lateral earth pressures do not include a factor of safety and do not provide for possible hydrostatic pressure on the walls. Responsive Resourceful Reliable 9

16 Geotechnical Engineering Report Union County Landfill Retaining Wall Wingate, North Carolina October 22, 2015 Terracon Project No Earth Pressure Conditions Active (Ka) At-Rest (Ko) Passive (Kp) Earth Pressure Coefficients Earth Pressure Coefficient for Backfill Type On-site soils 0.36 Imported granular soils 0.33 On-site soils 0.53 Imported granular soils 0.50 On-site soils 2.77 Imported granular soils 3.00 Equivalent Fluid Density (pcf) Surcharge Pressure, p 1 (psf) (0.36)S (0.33)S (0.53)S (0.50)S Earth Pressure, p 2 (psf) (43)H (40)H (64)H (60)H Applicable conditions to the above include: For active earth pressure, wall must rotate about base, with top lateral movements of about H to H, where H is wall height For passive earth pressure to develop, wall must move horizontally to mobilize resistance Uniform surcharge, where S is surcharge pressure In-situ soil backfill weight a maximum of 120 pcf Horizontal backfill, compacted to 95 percent of standard Proctor maximum dry density Unit weight of water (ɣ w) is 62.4 pcf Loading from heavy compaction equipment not included No hydrostatic pressures acting on wall No dynamic loading No safety factor included in soil parameters Ignore passive pressure in the upper 24 inches Responsive Resourceful Reliable 10

17 Geotechnical Engineering Report Union County Landfill Retaining Wall Wingate, North Carolina October 22, 2015 Terracon Project No Backfill placed against structures should consist of granular soils or low plasticity cohesive soils. For the granular values to be valid, the granular backfill must extend out from the base of the wall at an angle of at least 45 and 60 degrees from vertical for the active/at-rest and passive cases, respectively. High plasticity clay (CH) and elastic silt (MH) should not be used as backfill. To minimize the build-up of lateral soil pressures in excess of the recommended design pressures, over-compaction of the fill behind the wall should be avoided; however, a lesser degree of compaction may permit excessive post-construction settlements. In order to limit wall pressures resulting from over-compaction of wall backfill, we recommend that backfill within 5 feet of a wall be compacted by small, hand-operated compaction equipment to 95 percent of the standard Proctor maximum dry density. Remaining backfill should be compacted in accordance with the compaction recommendations provided in the Earthwork section of this report. 4.5 Global Slope Stability A slope stability analysis for the proposed retaining wall was performed at the cross section of the critical section of the retaining wall, i.e., the area along the wall alignment having the lowest existing elevation and potential for the wall to be at its tallest. The location of the critical section performed in our analysis is shown on Exhibit D-1 in Appendix D. The section selected for the slope stability analysis is based on our understanding of the proposed retaining wall, the existing topographic information provided by CDM Smith, and the borings that were completed along the proposed retaining wall alignment. The SLOPE/W computer program developed by Geo-Slope, Inc. was used for the slope stability analysis. The design parameters used in the analysis were based on the findings during our field exploration, laboratory testing results, literature research with regard to soil strength conditions, and our experience with similar soils in the project area. Please refer to the following table for the material strength parameters utilized for the slope stability analysis. Soil Strength Parameters Material c (psf) Effective Stress (Degrees) Total Unit Weight (pcf) Fill Soils Residual Soils PWR The failure surface with the minimum factor of safety for the soil strength parameters tabulated above is presented on Exhibit D-2 in Appendix D. The computer-generated outputs include the cross-section analyzed along with the failure surface representing the minimum factor of safety, Responsive Resourceful Reliable 11

18 Geotechnical Engineering Report Union County Landfill Retaining Wall Wingate, North Carolina October 22, 2015 Terracon Project No the center of the circle of that failure surface, and the entry and exit points of the failure surfaces that were analyzed. The minimum factor of safety for the section was determined to be greater than 2.3. It is our opinion that this factor of safety is sufficient for the proposed retaining wall under the conditions analyzed. 5.0 GENERAL COMMENTS Terracon should be retained to review the final design plans and specifications so comments can be made regarding interpretation and implementation of our geotechnical recommendations in the design and specifications. Terracon also should be retained to provide observation and testing services during grading, excavation, foundation construction and other earth-related construction phases of the project. The analysis and recommendations presented in this report are based upon the data obtained from the borings performed at the indicated locations and from other information discussed in this report. This report does not reflect variations that may occur between borings, across the site, or due to the modifying effects of construction or weather. The nature and extent of such variations may not become evident until during or after construction. If variations appear, we should be immediately notified so that further evaluation and supplemental recommendations can be provided. The scope of services for this project does not include either specifically or by implication any environmental or biological (e.g., mold, fungi, bacteria) assessment of the site or identification or prevention of pollutants, hazardous materials or conditions. If the owner is concerned about the potential for such contamination or pollution, other studies should be undertaken. This report has been prepared for the exclusive use of our client for specific application to the project discussed and has been prepared in accordance with generally accepted geotechnical engineering practices. No warranties, either express or implied, are intended or made. Site safety, excavation support, and dewatering requirements are the responsibility of others. In the event that changes in the nature, design, or location of the project as outlined in this report are planned, the conclusions and recommendations contained in this report shall not be considered valid unless Terracon reviews the changes and either verifies or modifies the conclusions of this report in writing. Responsive Resourceful Reliable 12

19 APPENDIX A FIELD EXPLORATION

20 TOPOGRAPHIC MAP IMAGE COURTESY OF THE U.S. GEOLOGICAL SURVEY QUADRANGLES INCLUDE: WATSON, NC (1/1/1987). DIAGRAM IS FOR GENERAL LOCATION ONLY, AND IS NOT INTENDED FOR CONSTRUCTION PURPOSES Project Manager: Project No CRB Drawn by: Checked by: KCM CRB Approved by: CRB SITE LOCATION MAP Exhibit Union County Landfill Retaining Wall A-1a Scale: 1 =24,000 SF File Name: A1 & A2 Date: 10/22/ E Starita Road Charlotte, NC Austin Chaney Road Wingate, NC

21 PROVIDED BY MICROSOFT BING MAPS DIAGRAM IS FOR GENERAL LOCATION ONLY, AND IS NOT INTENDED FOR CONSTRUCTION PURPOSES Project Manager: CRB Drawn by: KCM Checked by: CRB Approved by: CRB Project No Scale: AS SHOWN File Name: A1 & A2 Date: 10/22/ E Starita Road Charlotte, NC SITE LOCATION MAP Union County Landfill Retaining Wall 2125 Austin Chaney Road Wingate, NC Exhibit A-1b

22 LEGEND: = Approximate Location of Borings B-1 B-2 B-3 B-4 AERIAL PHOTOGRAPHY PROVIDED BY MICROSOFT BING MAPS DIAGRAM IS FOR GENERAL LOCATION ONLY, AND IS NOT INTENDED FOR CONSTRUCTION PURPOSES Project Manager: CRB Drawn by: KCM Checked by: CRB Approved by: CRB Project No Scale: AS SHOWN File Name: A1 & A2 Date: 10/22/ E Starita Road Charlotte, NC BORING LOCATION PLAN Union County Landfill Retaining Wall 2125 Austin Chaney Road Wingate, NC Exhibit A-2

23 Geotechnical Engineering Report Union County Landfill Retaining Wall Wingate, North Carolina October 22, 2015 Terracon Project No Field Exploration Description The boring locations were laid out on the site by Terracon personnel and were measured from available site features. Right angles for the boring locations were estimated. The locations of the borings should be considered accurate only to the degree implied by the means and methods used to define them. The borings were drilled with an ATV-mounted rotary drill rig using hollow stem augers to advance the boreholes. Samples of the soil encountered in the borings were obtained using the split-barrel sampling procedure. In the split barrel sampling procedure, the number of blows required to advance a standard 2 inch O.D. split barrel sampler the last 12 inches of the typical total 18 inch penetration by means of a 140 pound hammer with a free fall of 30 inches, is the standard penetration resistance value (SPT-N). This value is used to estimate the in-situ relative density of cohesionless soils and consistency of cohesive soils. An automatic SPT hammer was used to advance the split-barrel sampler in the borings performed on this site. A significantly greater efficiency is achieved with the automatic hammer compared to the conventional safety hammer operated with a cathead and rope. This higher efficiency has an appreciable effect on the SPT-N value. The effect of the automatic hammer's efficiency has been considered in the interpretation and analysis of the subsurface information for this report. The samples were tagged for identification, sealed to reduce moisture loss, and taken to our laboratory for further examination, testing, and classification. Information provided on the boring logs attached to this report includes soil descriptions, consistency evaluations, boring depths, sampling intervals, and groundwater conditions. The borings were backfilled with auger cuttings prior to the drill crew leaving the site. A field log of each boring was prepared by a staff professional. These logs included visual classifications of the materials encountered during drilling as well as the driller s interpretation of the subsurface conditions between samples. Final boring logs included with this report represent the engineer's interpretation of the field logs and include modifications based on laboratory observation and tests of the samples. Exhibit A-3

24 PROJECT: Union County Landfill Retaining Wall BORING LOG NO. B-1 CLIENT: CDM Smith Charlotte, North Carolina Page 1 of 1 SITE: GRAPHIC LOG DEPTH 0.3 4" TOPSOIL SANDY SILT (ML), light brown to brown with tan, white, red, and black, hard, residuum 3.0 Union County Landfill Wingate, North Carolina LOCATION See Exhibit A-2 PARTIALLY WEATHERED ROCK, sampled as light brown to brown with tan, white, red, and black sandy silt with rock fragments DEPTH (Ft.) WATER LEVEL OBSERVATIONS SAMPLE TYPE RECOVERY (In.) 16 8 FIELD TEST RESULTS N= /4" WATER CONTENT (%) ATTERBERG LIMITS LL-PL-PI PERCENT FINES 67 5 THIS BORING LOG IS NOT VALID IF SEPARATED FROM ORIGINAL REPORT. GEO SMART LOG-NO WELL BORING LOGS.GPJ TERRACON2015.GDT 10/22/ NO RECOVERY Auger Refusal at 19 Feet Stratification lines are approximate. In-situ, the transition may be gradual. Advancement Method: Hollow Stem Augers Abandonment Method: Borings backfilled with soil cuttings upon completion. WATER LEVEL OBSERVATIONS No Free Water Observed Dry Cave-In See Exhibit A-3 for description of field procedures. See Appendix B for description of laboratory procedures and additional data (if any). See Appendix C for explanation of symbols and abbreviations E Starita Road Charlotte, North Carolina Hammer Type: Automatic Notes: Boring Started: 9/30/2015 Drill Rig: CME-550X Project No.: /6" 50/2" 50/4" 50/1" 50/0" Boring Completed: 9/30/2015 Driller: J. Cain Exhibit: A-4

25 PROJECT: Union County Landfill Retaining Wall BORING LOG NO. B-2 CLIENT: CDM Smith Charlotte, North Carolina Page 1 of 1 SITE: GRAPHIC LOG DEPTH 0.4 5" TOPSOIL / STONE SANDY SILT (ML), light brown to brown with tan, white, red, and black, very stiff, residuum 3.0 Union County Landfill Wingate, North Carolina LOCATION See Exhibit A-2 PARTIALLY WEATHERED ROCK, sampled as light brown to brown with tan, white, red, and black sandy silt with rock fragments DEPTH (Ft.) WATER LEVEL OBSERVATIONS SAMPLE TYPE RECOVERY (In.) 12 5 FIELD TEST RESULTS N=29 50/5" WATER CONTENT (%) 6 ATTERBERG LIMITS LL-PL-PI PERCENT FINES /2" THIS BORING LOG IS NOT VALID IF SEPARATED FROM ORIGINAL REPORT. GEO SMART LOG-NO WELL BORING LOGS.GPJ TERRACON2015.GDT 10/22/ PARTIALLY WEATHERED ROCK, sampled as very light brown to very light gray sandy silt with rock fragments 20.5 Auger Refusal at 20.5 Feet Stratification lines are approximate. In-situ, the transition may be gradual. Advancement Method: Hollow Stem Augers Abandonment Method: Borings backfilled with soil cuttings upon completion. WATER LEVEL OBSERVATIONS No Free Water Observed Dry Cave-In See Exhibit A-3 for description of field procedures. See Appendix B for description of laboratory procedures and additional data (if any). See Appendix C for explanation of symbols and abbreviations E Starita Road Charlotte, North Carolina /4" 1 50/1" 1 50/1" 0 50/0" Hammer Type: Automatic Notes: Boring Started: 9/30/2015 Drill Rig: CME-550X Project No.: Boring Completed: 9/30/2015 Driller: J. Cain Exhibit: A-5

26 PROJECT: Union County Landfill Retaining Wall BORING LOG NO. B-3 CLIENT: CDM Smith Charlotte, North Carolina Page 1 of 1 SITE: GRAPHIC LOG Union County Landfill Wingate, North Carolina LOCATION See Exhibit A-2 DEPTH 0.3 3" TOPSOIL SANDY SILT (ML), trace gravel, light brown to brown with red and tan, very stiff to hard, residuum DEPTH (Ft.) WATER LEVEL OBSERVATIONS SAMPLE TYPE RECOVERY (In.) 8 FIELD TEST RESULTS N=29 WATER CONTENT (%) 8 ATTERBERG LIMITS LL-PL-PI PERCENT FINES 54 THIS BORING LOG IS NOT VALID IF SEPARATED FROM ORIGINAL REPORT. GEO SMART LOG-NO WELL BORING LOGS.GPJ TERRACON2015.GDT 10/22/ PARTIALLY WEATHERED ROCK, sampled as light brown to brown with tan, white, and red sandy silt PARTIALLY WEATHERED ROCK, sampled as very light brown to very light gray sandy silt with rock fragments PARTIALLY WEATHERED ROCK, sampled as very light gray sandy silt with rock fragments Auger Refusal at 28.1 Feet Stratification lines are approximate. In-situ, the transition may be gradual. Advancement Method: Hollow Stem Augers Abandonment Method: Borings backfilled with soil cuttings upon completion. WATER LEVEL OBSERVATIONS No Free Water Observed Dry Cave-In See Exhibit A-3 for description of field procedures. See Appendix B for description of laboratory procedures and additional data (if any). See Appendix C for explanation of symbols and abbreviations E Starita Road Charlotte, North Carolina Hammer Type: Automatic Notes: Boring Started: 9/30/2015 Drill Rig: CME-550X Project No.: N= /2" 50/4" 50/3" 50/1" 50/1" 50/1" 23 Boring Completed: 9/30/2015 Driller: J. Cain Exhibit: A-6

27 PROJECT: Union County Landfill Retaining Wall BORING LOG NO. B-4 CLIENT: CDM Smith Charlotte, North Carolina Page 1 of 1 SITE: GRAPHIC LOG Union County Landfill Wingate, North Carolina LOCATION See Exhibit A-2 DEPTH 0.3 4" STONE PARTIALLY WEATHERED ROCK, sampled as light brown and brown to very light gray sandy silt with rock fragments DEPTH (Ft.) WATER LEVEL OBSERVATIONS SAMPLE TYPE RECOVERY (In.) 3 FIELD TEST RESULTS 50/3" WATER CONTENT (%) ATTERBERG LIMITS LL-PL-PI PERCENT FINES 2 50/2" /2" THIS BORING LOG IS NOT VALID IF SEPARATED FROM ORIGINAL REPORT. GEO SMART LOG-NO WELL BORING LOGS.GPJ TERRACON2015.GDT 10/22/ Auger Refusal at 15 Feet Stratification lines are approximate. In-situ, the transition may be gradual. Advancement Method: Hollow Stem Augers Abandonment Method: Borings backfilled with soil cuttings upon completion. WATER LEVEL OBSERVATIONS No Free Water Observed Dry Cave-In See Exhibit A-3 for description of field procedures. See Appendix B for description of laboratory procedures and additional data (if any). See Appendix C for explanation of symbols and abbreviations E Starita Road Charlotte, North Carolina /5" 1 50/1" 0 50/0" Hammer Type: Automatic Notes: Boring Started: 9/30/2015 Drill Rig: CME-550X Project No.: Boring Completed: 9/30/2015 Driller: J. Cain Exhibit: A-7

28 APPENDIX B LABORATORY TESTING

29 Geotechnical Engineering Report Union County Landfill Retaining Wall Wingate, North Carolina October 22, 2015 Terracon Project No Laboratory Testing Samples retrieved during the field exploration were taken to the laboratory for further observation by the project geotechnical engineer and were classified in accordance with the Unified Soil Classification System (USCS) described in Appendix A. At that time, the field descriptions were confirmed or modified as necessary. Moisture content, Atterberg Limits, and wash no. 200 sieve tests were conducted in general accordance with the applicable ASTM standards on selected soil samples and the test results are presented on the boring logs. Laboratory tests were conducted on selected soil samples. The laboratory test results were used for the geotechnical engineering analyses, and the development of earthwork and lateral earth pressure recommendations. Laboratory tests were performed in general accordance with the applicable ASTM, local or other accepted standards. Selected soil samples obtained from the site were tested for the following engineering properties: In-situ Water Content Sieve Analysis Atterberg Limits Descriptive classifications of the soils indicated on the boring logs are in accordance with the enclosed General Notes and the Unified Soil Classification System. Also shown are estimated Unified Soil Classification Symbols. A brief description of this classification system is included in Appendix C of this report. All classification was by visual manual procedures. Selected samples were further classified using the results of Material Finer than No. 200 Sieve and Atterberg limits testing. The Water Content, Material Finer than No. 200 Sieve and Atterberg limits test results are provided on the boring logs. The following table summarizes the in-situ moisture content, wash No. 200 sieve tests, and Atterberg Limits test results. These results are also shown on the boring logs in Appendix A. Sample Location Depth, (feet) In-situ Moisture Content, (%) % Passing the No. 200 Sieve Liquid Limit, (%) Plastic Limit, (%) Plasticity Index, (%) B B B B Exhibit B-1

30 APPENDIX C SUPPORTING DOCUMENTS

31 DESCRIPTION OF SYMBOLS AND ABBREVIATIONS GENERAL NOTES Water Initially Encountered N Standard Penetration Test Resistance (Blows/Ft.) SAMPLING Standard Penetration Test WATER LEVEL Water Level After a Specified Period of Time Water Level After a Specified Period of Time Water levels indicated on the soil boring logs are the levels measured in the borehole at the times indicated. Groundwater level variations will occur over time. In low permeability soils, accurate determination of groundwater levels is not possible with short term water level observations. FIELD TESTS (HP) (T) (DCP) (PID) (OVA) Hand Penetrometer Torvane Dynamic Cone Penetrometer Photo-Ionization Detector Organic Vapor Analyzer DESCRIPTIVE SOIL CLASSIFICATION Soil classification is based on the Unified Soil Classification System. Coarse Grained Soils have more than 50% of their dry weight retained on a #200 sieve; their principal descriptors are: boulders, cobbles, gravel or sand. Fine Grained Soils have less than 50% of their dry weight retained on a #200 sieve; they are principally described as clays if they are plastic, and silts if they are slightly plastic or non-plastic. Major constituents may be added as modifiers and minor constituents may be added according to the relative proportions based on grain size. In addition to gradation, coarse-grained soils are defined on the basis of their in-place relative density and fine-grained soils on the basis of their consistency. LOCATION AND ELEVATION NOTES Unless otherwise noted, Latitude and Longitude are approximately determined using a hand-held GPS device. The accuracy of such devices is variable. Surface elevation data annotated with +/- indicates that no actual topographical survey was conducted to confirm the surface elevation. Instead, the surface elevation was approximately determined from topographic maps of the area. RELATIVE DENSITY OF COARSE-GRAINED SOILS (More than 50% retained on No. 200 sieve.) Density determined by Standard Penetration Resistance CONSISTENCY OF FINE-GRAINED SOILS (50% or more passing the No. 200 sieve.) Consistency determined by laboratory shear strength testing, field visual-manual procedures or standard penetration resistance STRENGTH TERMS Descriptive Term (Density) Standard Penetration or N-Value Blows/Ft. Very Loose 0-3 Loose Medium Dense Dense Descriptive Term (Consistency) Unconfined Compressive Strength Qu, (psf) Very Soft less than Soft Medium Stiff Stiff 500 to 1,000 1,000 to 2,000 2,000 to 4,000 Standard Penetration or N-Value Blows/Ft Very Dense > 50 Very Stiff 4,000 to 8, Hard > 8,000 > 30 RELATIVE PROPORTIONS OF SAND AND GRAVEL Descriptive Term(s) of other constituents Percent of Dry Weight Major Component of Sample GRAIN SIZE TERMINOLOGY Particle Size Trace With Modifier < > 30 Boulders Cobbles Gravel Sand Silt or Clay Over 12 in. (300 mm) 12 in. to 3 in. (300mm to 75mm) 3 in. to #4 sieve (75mm to 4.75 mm) #4 to #200 sieve (4.75mm to 0.075mm Passing #200 sieve (0.075mm) RELATIVE PROPORTIONS OF FINES Descriptive Term(s) of other constituents Trace With Modifier Percent of Dry Weight < > 12 Term Non-plastic Low Medium High PLASTICITY DESCRIPTION Plasticity Index > 30 Exhibit: C-1

32 UNIFIED SOIL CLASSIFICATION SYSTEM Criteria for Assigning Group Symbols and Group Names Using Laboratory Tests A Coarse Grained Soils: More than 50% retained on No. 200 sieve Fine-Grained Soils: 50% or more passes the No. 200 sieve Gravels: More than 50% of coarse fraction retained on No. 4 sieve Sands: 50% or more of coarse fraction passes No. 4 sieve Silts and Clays: Liquid limit less than 50 Silts and Clays: Liquid limit 50 or more Clean Gravels: Less than 5% fines C Gravels with Fines: More than 12% fines C Clean Sands: Less than 5% fines D Sands with Fines: More than 12% fines D Inorganic: Organic: Inorganic: Organic: Group Symbol Soil Classification Group Name B Cu 4 and 1 Cc 3 E GW Well-graded gravel F Cu 4 and/or 1 Cc 3 E GP Poorly graded gravel F Fines classify as ML or MH GM Silty gravel F,G,H Fines classify as CL or CH GC Clayey gravel F,G,H Cu 6 and 1 Cc 3 E SW Well-graded sand I Cu 6 and/or 1 Cc 3 E SP Poorly graded sand I Fines classify as ML or MH SM Silty sand G,H,I Fines classify as CL or CH SC Clayey sand G,H,I PI 7 and plots on or above A line J CL Lean clay K,L,M PI 4 or plots below A line J ML Silt K,L,M Liquid limit - oven dried Organic clay K,L,M,N 0.75 OL Liquid limit - not dried Organic silt K,L,M,O PI plots on or above A line CH Fat clay K,L,M PI plots below A line MH Elastic Silt K,L,M Liquid limit - oven dried Liquid limit - not dried Highly organic soils: Primarily organic matter, dark in color, and organic odor PT Peat 0.75 OH Organic clay K,L,M,P Organic silt K,L,M,Q A Based on the material passing the 3-inch (75-mm) sieve B If field sample contained cobbles or boulders, or both, add with cobbles or boulders, or both to group name. C Gravels with 5 to 12% fines require dual symbols: GW-GM well-graded gravel with silt, GW-GC well-graded gravel with clay, GP-GM poorly graded gravel with silt, GP-GC poorly graded gravel with clay. D Sands with 5 to 12% fines require dual symbols: SW-SM well-graded sand with silt, SW-SC well-graded sand with clay, SP-SM poorly graded sand with silt, SP-SC poorly graded sand with clay E Cu = D 60/D 10 Cc = D (D ) 2 x D 60 F If soil contains 15% sand, add with sand to group name. G If fines classify as CL-ML, use dual symbol GC-GM, or SC-SM. H If fines are organic, add with organic fines to group name. I If soil contains 15% gravel, add with gravel to group name. J If Atterberg limits plot in shaded area, soil is a CL-ML, silty clay. K If soil contains 15 to 29% plus No. 200, add with sand or with gravel, whichever is predominant. L If soil contains 30% plus No. 200 predominantly sand, add sandy to group name. M If soil contains 30% plus No. 200, predominantly gravel, add gravelly to group name. N PI 4 and plots on or above A line. O PI 4 or plots below A line. P PI plots on or above A line. Q PI plots below A line. Exhibit C-2

33 APPENDIX D SLOPE STABILITY ANALYSIS

34 LEGEND: = Approximate Location of Slope Stability Analysis = Approximate Location of Soil Test Borings B-1 A B-2 A B-3 B-4 DIAGRAM IS FOR GENERAL LOCATION ONLY, AND IS NOT INTENDED FOR CONSTRUCTION PURPOSES Project Manager: CRB Drawn by: KCM Checked by: CRB Approved by: DJC Project No Scale: AS SHOWN File Name: D-1 SSSP Date: 10/22/ Starita Road, Suite E Charlotte, North Carolina PH. (704) FAX. (704) SLOPE STABILITY SECTION PLAN Union County Landfill Retaining Wall 2125 Austin Chaney Road Wingate, NC EXHIBIT D-1

35 Minimum Factor of Safety Center of Failure Surface Traffic Surcharge = 300 psf Note: Slope/W computer software developed by GeoStudio was utilized in our analysis. DIAGRAM IS FOR GENERAL LOCATION ONLY, AND IS NOT INTENDED FOR CONSTRUCTION PURPOSES Project Manager: CRB Drawn by: KCM Checked by: CRB Approved by: DJC Project No Scale: AS SHOWN File Name: D-2 A-A Date: 10/22/ Starita Road, Suite E Charlotte, North Carolina PH. (704) FAX. (704) SLOPE STABILITY SECTION A-A Union County Landfill Retaining Wall 2125 Austin Chaney Road Wingate, NC EXHIBIT D-2