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ST16-01A-SY2411011 Geotechnical Engineering Report Monument Signs Coppell, Texas May 9, 2018 Terracon Project No. 94175221 Prepared for: Halff Associates, Inc. Richardson, Texas Prepared by: Terracon Consultants, Inc. Dallas, Texas Terracon Consultants, Inc.8901 Carpenter Freeway, Suite 100 Dallas, Texas 75247 Registration No. F-3272 P [214] 630 1010 F [214] 630 7070 terracon.com May 9, 2018 Halff Associates, Inc. 1201 N. Bowser Road Dallas, TX 75081 Attn: Mr. Jeff Roberts, PE E: jfroberts@halff.com Re: Geotechnical Engineering Report Monument Signs Southwestern Boulevard and S. Belt Line Road Coppell, Texas Terracon Project No. 94175221 Dear Mr. Roberts: This report presents the findings of our subsurface exploration and provides geotechnical recommendations for the design of the monument signs. This study was performed in general accordance with our Proposal No. P94175221 dated October 5, 2017. We appreciate the opportunity to be of service to you on this project. If you have any questions concerning this report, or if we may be of further service, please contact us. Sincerely, Terracon Consultants, Inc. Texas Registration #3272 Siva P. Pathivada, P.E.Tim G. Abrams, P.E. Department Manager I Senior Principal Minh Le, Ph.D., P.E. Project Manager TABLE OF CONTENTS Page EXECUTIVE SUMMARY ............................................................................................................. i 1.0 INTRODUCTION .............................................................................................................1 2.0 PROJECT INFORMATION .............................................................................................1 2.1 Project Description ...............................................................................................1 2.2 Site Location and Description...............................................................................1 3.0 SUBSURFACE CONDITIONS ........................................................................................2 3.1 Geology ...............................................................................................................2 3.2 Typical Profile ......................................................................................................2 3.3 Groundwater ........................................................................................................3 4.0 RECOMMENDATIONS FOR DESIGN AND CONSTRUCTION ......................................3 4.1 Geotechnical Considerations ...............................................................................3 4.2 Earthwork.............................................................................................................4 4.2.1 Site Preparation ........................................................................................4 4.2.2 Material Types ..........................................................................................4 4.2.3 Compaction Requirements .......................................................................4 4.3 Foundation Recommendations ............................................................................4 4.3.1 Shallow Footings – Design Parameters ....................................................5 4.3.2 Shallow Footings - Construction Considerations .......................................5 4.3.3 Underreamed Shafts - Axial Capacity .......................................................6 4.3.4 Underreamed Shafts - Lateral Capacity ....................................................7 4.3.5 Underreamed Shafts - Soil Induced Uplift Loads ......................................7 4.3.6 Underreamed Shafts – Uplift Resistance ..................................................7 4.3.7 Underreamed Shafts Construction Considerations ...................................7 4.4 Seismic Considerations........................................................................................8 5.0 GENERAL COMMENTS .................................................................................................8 APPENDIX A – FIELD EXPLORATION Exhibits A-1 through A-3 Boring Location Plans Exhibit A-4 Field Exploration Description Exhibits A-5 through A-7 Boring Logs APPENDIX B – LABORATORY TESTING Exhibit B-1 Laboratory Testing APPENDIX C – SUPPORTING DOCUMENTS Exhibit C-1 General Notes Exhibit C-2 Unified Soil Classification System Geotechnical Engineering Report Monument Signs Coppell, Texas May 9, 2018 Terracon Project No. 94175221 Responsive Resourceful Reliable i EXECUTIVE SUMMARY A geotechnical engineering exploration has been completed for the proposed monument signs to be located on Southwestern Boulevard and S. Belt Line Road in Coppell, Texas. Three (3) borings were sampled to depths of approximately 20 and 40 feet. The following geotechnical considerations were identified. n The subsurface soils consisted of fill materials, fat clays, lean clays underlain by gray shale. A sand layer was encountered in Boring B-2 to the boring termination depth of 20 feet. Groundwater was found in the borings at depth of 13 to 27 feet during drilling and 12 to 18 feet after completion of drilling. n Expansive clay soils are present at all three monument locations. The expansive clay soils can subject shallow foundations bearing in them to differential movements due to moisture fluctuations in the soils. The monument signs on Southwestern Boulevard (Borings B-1 and B-2) are recommended to be supported on shallow footing foundations founded at depths of 4 to 6 feet to reduce potential future movements. The monument sign on S. Belt Line Road (Boring B-3) is recommended to be supported by underreamed shaft foundations bearing in natural clays. n Based on the 2015 International Building Code and ASCE/SEI 7-10, seismic site classification for this site is C. 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 1 GEOTECHNICAL ENGINEERING REPORT MONUMENT SIGNS COPPELL, TEXAS Terracon Project No. 94175221 May 9, 2018 1.0 INTRODUCTION New monument signs are planned on Southwestern Blvd. and S. Belt Line Road in Coppell, Texas. Terracon’s scope of services included drilling and sampling three soil borings, laboratory testing, and engineering analysis. The purpose of these services is to provide information and geotechnical engineering recommendations relative to: §subsurface soil conditions §foundation design and construction §groundwater conditions §seismic considerations 2.0 PROJECT INFORMATION 2.1 Project Description ITEM DESCRIPTION Site layout See Appendix A: Exhibits A-1 through A-3: Boring Location Plans Planned signs Monument signs with height less than 5 feet (assumed) Finished grade elevation Assumed within 2 feet of existing grade elevations. 2.2 Site Location and Description ITEM DESCRIPTION Locations Two signs are located on Southwestern Boulevard near S. Belt Line Road (see Exhibit A-2) One sign is located on S. Belt Line Road between Dividend Drive and Hackberry Road (see Exhibit A-3) Existing improvements Roadway pavements and shoulders Current ground cover Concrete and grass Existing topography Relatively level Geotechnical Engineering Report Monument Signs Coppell, Texas May 9, 2018 Terracon Project No. 94175221 Responsive Resourceful Reliable 2 3.0 SUBSURFACE CONDITIONS 3.1 Geology Review of surface geology maps indicates the site is situated on alluvial and terrace deposits of the Trinity River System (presented in Borings B-1 and B-2) over the Eagle Ford Formation of Cretaceous age (presented in Boring B-3). The alluvial and terrace deposits consist of clays, sandy clays and clayey sands. Residual clays of high plasticity are formed by the Eagle Ford Formation above the shale. These soils are noted for their ability to experience large volume changes with fluctuations in their moisture content. The Eagle Ford is a dark gray to gray shale with occasional seams and thin layers of limestone. Calcareous concretions, often exceeding 12 inches in diameter, are found throughout the Eagle Ford Formation, as well as occasional thin layers and nodules of pyrite and chert. The Eagle Ford is anticipated to be over 200 feet thick at this site. The Eagle Ford is not water bearing, but it serves as an aquatard when overlain by more recent alluvial and terrace deposits. Perched groundwater is often present in the alluvial and terrace deposits. 3.2 Typical Profile The subsurface conditions were explored by drilling three borings to depths of 20 and 40 feet at the approximate locations indicated in Exhibits A-1 through A-3. A description of the field work is presented in Exhibit A-4. Boring logs are presented in Exhibits A-5 through A-7. Conditions encountered at the boring locations are indicated on the 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. Laboratory tests were performed to classify the soil, and measure soil strength. Brief descriptions and results of these tests are presented in Appendix B. Borings B-1 and B-2 encountered expansive clay fill to depths of 1.5 to 2 feet. The fill was underlain by expansive clays to a depth of 12 feet in Boring B-2 and to a depth of 17 feet in Boring B-1. A sandy lean clay layer was present below 17 feet in Boring B-1. In Boring B-2, a moderately active sandy clay was present between 12 and 16 feet. The sandy clay layer was underlain by a clayey sand layer to the termination depth of 20 feet. Boring B-3 encountered expansive fat clays to a depth of 38 feet underlain by gray shale bedrock to the termination depth of 40 feet. Geotechnical Engineering Report Monument Signs Coppell, Texas May 9, 2018 Terracon Project No. 94175221 Responsive Resourceful Reliable 3 3.3 Groundwater The borings were advanced using dry auger drilling techniques, which allows short-term groundwater observations to be made while drilling. Groundwater was measured during and immediately after drilling as shown in table below. Groundwater Measurement Boring During Drilling, feet After Drilling, feet B-1 13 13 B-2 14 12 B-3 27 18 The groundwater level observations provide an indication of groundwater conditions present at the site at the time of drilling. Groundwater level fluctuations 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 vary. 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 Expansive clay soils are present at three monument locations. These soils are prone to volume change with variations in moisture level. The expansive clay soils can subject shallow foundations bearing in them to differential movements due to moisture fluctuations in the soils. We estimate the potential magnitude of post construction heave at this site to be on the order of 3 to 4 inches for dry soil conditions at Borings B-1 and B-2; and on the order of 5 to 6 inches for dry soil conditions at Boring B-3. The monument signs on Southwestern Boulevard located near Borings B-1 and B-2 are recommended to be supported on shallow footing foundations. The monument sign on S. Belt Line Road near Boring B-3 is recommended to be supported by underreamed shaft foundations bearing in natural clays. Geotechnical recommendations for earthwork and foundations for the project are presented in the following report sections. Geotechnical Engineering Report Monument Signs Coppell, Texas May 9, 2018 Terracon Project No. 94175221 Responsive Resourceful Reliable 4 4.2 Earthwork 4.2.1 Site Preparation All the existing vegetation and deleterious materials should be removed. Any soft or pumping areas should be excavated to firm ground. Excavated areas should be backfilled with properly placed and compacted fill as discussed Section 4.2.3 Compaction Requirements. 4.2.2 Material Types Fill materials should meet the criteria given below. Nomenclature Technical Description Appropriate Use On-site soils Free of vegetation, organic material, debris, and rocks greater than 4 inches in maximum dimension §General site grading Imported fill Clean clay soil (free of deleterious material and debris) with a liquid limit (LL) less than 60 and no rock greater than 4 inches in maximum dimension 4.2.3 Compaction Requirements The recommended compaction criteria are presented in the following table. We recommend that all 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. Type of Fill Compaction Criteria Subgrade preparation to receive fill Surface scarified to a minimum depth of 6 inches and compacted to the criteria provided below. All fills; loose lift thickness 9-inch or less. General site fill A minimum of 95% maximum standard Proctor dry density (ASTM D 698) at a minimum of 2 percentage points above optimum moisture content. 4.3 Foundation Recommendations The monument signs on Southwestern Boulevard near Borings B-1 and B-2 are recommended to be supported on shallow footing foundations founded at a depth of 4 feet to reduce potential future movements. The monument sign on S. Belt Line Road near Boring B-3 is recommended to be supported by underreamed shaft foundations bearing in natural clays to reduce potential future movements. Geotechnical Engineering Report Monument Signs Coppell, Texas May 9, 2018 Terracon Project No. 94175221 Responsive Resourceful Reliable 5 4.3.1 Shallow Footings – Design Parameters The proposed monument signs on Southwestern Boulevard (Borings B-1 and B-2) can be supported by shallow footing foundations bearing in the natural clays at depths of 4 to 6 feet. Estimated potential movements of shallow footing foundation bearing in the natural clays at a depth of 4 feet are about 2 inches. Estimated potential movements of shallow footing foundation bearing in the natural clays at a depth of 6 feet are about 1 inch. Design recommendations for spread footings and continuous footings are presented in the following table. Description Continuous Footing Individual Footing Bearing stratum Natural clays at 4 to 6 feet deep Net allowable bearing pressure1 3,000 psf 3,500 psf Minimum dimension 18 inches 36 inches Minimum embedment below lowest adjacent finished grade 24 inches Approximate differential settlement 50 to 75 percent of total settlement Ultimate passive pressure2,3 235 psf/ft triangular distribution Ultimate Coefficient of sliding friction 2,3 0.32 1.The recommended net allowable bearing pressure is the pressure in excess of the minimum surrounding overburden pressure at the footing base elevation. 2.The sides of the excavation for the spread footing foundation must be nearly vertical and the concrete should be placed neat against these vertical faces for the passive earth pressure values to be valid. If the loaded side is sloped or benched, and then backfilled, the allowable passive pressure will be significantly reduced. Passive resistance in the upper 2 feet of the soil profile should be neglected. 3.A minimum safety factor of 1.5 should be used for sliding failure. If the signs are subject to significant wind load to cause overturning, overturning resistance for spread footing foundations may be computed as the sum of the weight of the foundation element, the weight of the soil overlying the foundation and soil bearing resistance. We recommend using a soil unit weight of 120 pcf for compacted structural fill overlying the footing placed as described in Section 4.2 Earthwork. We recommend a minimum factor of safety of 1.5 be utilized for uplift calculations. 4.3.2 Shallow Footings - Construction Considerations Shallow footings excavations should be protected from standing water or desiccation. The base of all foundation excavations should be free of water and loose soil and rock prior to placing concrete. Excavation of individual footings or sections of continuous footings, placement of steel and concrete, and backfilling should be completed in a reasonably continuous manner. It is recommended that complete installation of individual footings or sections of continuous footings Geotechnical Engineering Report Monument Signs Coppell, Texas May 9, 2018 Terracon Project No. 94175221 Responsive Resourceful Reliable 6 be accomplished within 48 hours of excavation to prevent drying of the soils supporting the footings. If the soils at bearing level become dry with presence of desiccation cracks, disturbed or soft, or frozen, the affected soil should be removed prior to placing concrete. A lean concrete mud-mat over the bearing soils should be placed if the excavations must remain open for an extended period of time. Backfilling adjacent and over shallow footings should proceed as soon as practical to reduce disturbance. Backfilling should be accomplished using soils similar to those excavated. All backfill should be properly compacted to the criteria presented in Section 4.2.3 Compaction Requirements. All footing installations should be inspected by qualified geotechnical personnel to help verify the design depth and perform related duties. 4.3.3 Underreamed Shafts - Axial Capacity The monument sign on S. Belt Line Road (Boring B-3) is recommended to be supported by underreamed shaft foundations bearing in natural clays to reduce the potential movements. Design parameters for underreamed shaft foundations are presented in the following table. Design Parameter Recommendation Bearing stratum Tan and gray fat clay (CH) Bearing elevation 18 feet below finished grade. Allowable end bearing capacity 6,000 psf Minimum bell to shaft diameter ratio 2 to 1 Maximum bell to shaft diameter ratio 3 to 1 Minimum bell diameter 24 inches larger than the straight shaft portion. Minimum shaft diameter 18 inches Minimum underream edge to underream edge spacing One underream diameter, based on the larger of the two. Closer drilled shaft spacing should be evaluated by Terracon to determine if reductions in the allowable bearing pressures should be made to control settlement. Total settlement 70 to 80 percent of the foundation settlement is expected to occur as the shafts are loaded. The total settlement is estimated to range from ½ to 1 percent of the underream diameter. Differential settlement ½ to ¾ of the total settlement Geotechnical Engineering Report Monument Signs Coppell, Texas May 9, 2018 Terracon Project No. 94175221 Responsive Resourceful Reliable 7 4.3.4 Underreamed Shafts - Lateral Capacity The underreamed drilled shafts may be subject to lateral loads. Parameters for lateral load analysis are provided in the following table for use in Ensoft’s L-PILE computer program. Design Parameter Clay Soils from 0 to 18 feet LPILE material type Stiff clay w/o water Effective soil unit weight (pcf)125 Undrained cohesion, c (psf)2,150 Strain Factor,50 0.007 4.3.5 Underreamed Shafts - Soil Induced Uplift Loads The underreamed drilled shafts will be subject to uplift as a result of heave in the overlying clay soils. The magnitude of these loads vary with the shaft diameter, soil parameters, and particularly the in-situ moisture levels at the time of construction. The shafts must contain sufficient continuous vertical reinforcing to resist the net tensile load. Underreamed shaft foundations must be designed with adequate embedment into the bearing stratum to resist the uplift forces. The uplift load can be approximated by assuming a uniform uplift of 1,800 psf over the shaft perimeter to a depth of 10 feet. 4.3.6 Underreamed Shafts – Uplift Resistance The adequacy of the uplift resistance of the existing underreamed shafts when the underreamed shafts were first constructed can be estimated from the equations presented in the tables below for a depth of seasonal moisture change of 10 feet. Design Parameter Underreamed Shaft Uplift Design Recommendation Allowable Uplift Resistance, Q Uplift Allow (Factor of Safety of 2) QUplift Allow = 870 x Nu x (B2 – S2), lbs. Where, Nu = 4.57 (Db/B-0.75) for 0 < (Db/B) < 2.5 Nu = 8 for (Db/B) 2.5 Db = Embedment depth below active zone, feet (D b = Depth of bottom of bell – 6 feet) B = Bell Diameter, feet S = Shaft Diameter, feet 4.3.7 Underreamed Shafts Construction Considerations The construction of all underreamed drilled shafts should be observed by experienced geotechnical personnel during construction to confirm: 1) the bearing stratum; 2) the minimum bearing depth; 3) the removal of all cuttings 4) that groundwater seepage, if any, is correctly Geotechnical Engineering Report Monument Signs Coppell, Texas May 9, 2018 Terracon Project No. 94175221 Responsive Resourceful Reliable 8 handled; and 5) that the shafts are within acceptable vertical tolerance. Recommendations for drilled shaft construction are presented in the following table. Item Recommendation Drilled shaft installation specification Current version of American Concrete Institute’s “Standard Specification for the Construction of Drilled Piers” ACI 336. Top of shaft completion Enlarged (mushroom-shaped) top in contact with the clays should not be allowed. Time to complete Drilled and underreamed shafts should be completed in one day. Installation methods Shaft excavations should be installed using dry methods. The concrete should have a slump of 6 inches plus or minus 1 inch and be placed in a manner to avoid striking the reinforcing steel during placement. Groundwater control Seepage was observed in the boring during drilling. If groundwater seepage is encountered during the installation of underreamed shafts, shafts can be elevated slightly to avoid the seepage. Terracon should be contacted for additional recommendations if shafts must be elevated more than 2 feet. 4.4 Seismic Considerations Site Classification SDS SD1 2015 International Building Code (IBC)1 C 2 0.079 g 0.059g 1. In general accordance with the ASCE/SEI 7-10. 2.The ASCE/SEI 7-10 requires a site soil profile determination extending to a depth of 100 feet for seismic site classification. The current scope does not include the required 100 foot soil profile determination. Borings were extended to a maximum depth of approximately 40 feet and this seismic site class definition considers that gray limestone exists below the maximum depth of the subsurface exploration, which is consistent with the site geology. Additional exploration to deeper depths would be required to confirm the conditions below the current depth of exploration. Alternatively, a geophysical exploration could be utilized in order to attempt to justify a higher seismic site class. 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 Geotechnical Engineering Report Monument Signs Coppell, Texas May 9, 2018 Terracon Project No. 94175221 Responsive Resourceful Reliable 9 report. This report does not reflect variations that may occur between borings, across the site, or due to the modifying effects of weather. The nature and extent of such variations may not become evident until during or after construction. If variations appear, we should be immediately notified so that further evaluation and supplemental recommendations can be provided. The scope of services for this project does not include either specifically or by implication any environmental or biological (e.g., mold, fungi, bacteria) assessment of the site or identification or prevention of pollutants, hazardous materials or conditions. If the owner is concerned about the potential for such contamination or pollution, other studies should be undertaken. This report has been prepared for the exclusive use of our client for specific application to the project discussed and has been prepared in accordance with generally accepted geotechnical engineering practices. No warranties, either express or implied, are intended or made. Site safety, excavation support, and dewatering requirements are the responsibility of others. In the event that changes in the nature, design, or location of the project as outlined in this report are planned, the conclusions and recommendations contained in this report shall not be considered valid unless Terracon reviews the changes and either verifies or modifies the conclusions of this report in writing. APPENDIX A FIELD EXPLORATION EXPLORATION PLAN Monument Signs Southwestern Blvd and S Belt Line Rd Coppell, TX 8901 Carpenter Fwy Ste 100 Dallas, TX 75247-4547 DIAGRAM IS FOR GENERAL LOCATION ONLY, AND IS NOT INTENDED FOR CONSTRUCTION PURPOSES 94175221 AERIAL PHOTOGRAPHY PROVIDED BY MICROSOFT BING MAPS ML SP TA AS SHOWN 04/06/2018 Scale: A-1 ExhibitProjectManager: Drawn by: Checked by: Approved by: Project No. File Name: Date: ML BORING LOCATION PLAN Monument Signs Southwestern Blvd. and S. Belt Line Rd. Coppell, TX 8901 Carpenter Fwy Ste 100 Dallas, TX 75247-4547 DIAGRAM IS FOR GENERAL LOCATION ONLY, AND IS NOT INTENDED FOR CONSTRUCTION PURPOSES 94175221 AERIAL PHOTOGRAPHY PROVIDED BY MICROSOFT BING MAPS ML TA TA AS SHOWN 05/02/2018 Scale: A-2 ExhibitProjectManager: Drawn by: Checked by: Approved by: Project No. File Name: Date: ML EXPLORATIONPLAN8901CarpenterFwySte100Dallas,TX75247-454794175221AERIALPHOTOGRAPHYPROVIDEDBYMICROSOFTBINGMAPSMonumentSignsSouthwesternBlvd.andS.BeltLineRd.Coppell,TXDIAGRAMISFORGENERALLOCATIONONLY,ANDISNOTINTENDEDFORCONSTRUCTIONPURPOSESProjectManager:Drawnby:Checkedby:Approvedby:MLTATAML05/02/2018Scale:ProjectNo.FileName:Date:ASSHOWNA-3Exhibit Geotechnical Engineering Report Monument Signs Coppell, Texas May 9, 2018 Terracon Project No. 94175221 Responsive Resourceful Reliable Exhibit A-4 Field Exploration Description Subsurface conditions were explored by drilling 3 borings to depths of about 20 and 40 feet at the approximate locations indicated on the Boring Location Plan on Exhibit A-1 in this Appendix . The field exploration was performed on September 25, 2017. The test locations were established in the field by a handheld GPS unit. The elevations of the borings were obtained from the North Central Texas Council of Governments (NCTCOG) topographical maps of the site. The boring locations and elevations should be considered accurate only to the degree implied by the methods employed to determine them. The borings were performed using truck-mounted drill rigs. The soil samples encountered in the borings were obtained using thin walled tubes and split spoon sampling procedures. The samples were tagged for identification, sealed to reduce moisture loss, and taken to the laboratory for further examination, testing, and classification. The load-carrying capacity of the shale (bedrock) was evaluated in place by the Texas Department of Transportation (TxDOT) cone penetration test. Upon the completion of drilling, the boreholes were backfilled with soil cuttings. Field logs of the borings were prepared by the drill crew. The logs included visual classifications of the materials encountered as well as interpretation of the subsurface conditions between samples. The boring logs included with this report represent the engineer’s interpretation of the field logs and include modifications based on laboratory evaluation of the samples. The boring logs are presented on Exhibits A-5 through A-7 in Appendix A. General Notes to log terms and symbols are presented on Exhibit C-1 in Appendix C. APPENDIX B LABORATORY TESTING Geotechnical Engineering Report Monument Signs Coppell, Texas May 9, 2018 Terracon Project No. 94175221 Responsive Resourceful Reliable Exhibit B-1 Laboratory Testing The boring logs and samples were reviewed by a geotechnical engineer who selected soil samples for testing. Tests were performed by technicians working under the direction of the engineer. A brief description of the tests performed follows. Liquid and plastic limit tests and moisture content measurements were performed to aid in classifying the soils in accordance with the Unified Soil Classification System (USCS). The USCS is summarized on Exhibit C-2 in Appendix C. Strength of cohesive soils was measured by unconfined compressive strength and hand penetrometer tests. The laboratory test results are provided on the boring logs in Appendix A. APPENDIX C SUPPORTING DOCUMENTS Responsive ■Resourceful ■Reliable Exhibit C-1 EXHIBIT C-2 UNIFIED SOIL CLASSIFICATION SYSTEM Criteria for Assigning Group Symbols and Group Names Using Laboratory Tests A Soil Classification Group Symbol Group Name B Coarse Grained Soils: More than 50% retained on No. 200 sieve Gravels: More than 50% of coarse fraction retained on No. 4 sieve Clean Gravels: Less than 5% fines C Cu ‡ 4 and 1 £ Cc £ 3 E GW Well-graded gravel F Cu < 4 and/or 1 > Cc > 3 E GP Poorly graded gravel F Gravels with Fines: More than 12% fines C Fines classify as ML or MH GM Silty gravel F,G, H Fines classify as CL or CH GC Clayey gravel F,G,H Sands: 50% or more of coarse fraction passes No. 4 sieve Clean Sands: Less than 5% fines D Cu ‡ 6 and 1 £ Cc £ 3 E SW Well-graded sand I Cu < 6 and/or 1 > Cc > 3 E SP Poorly graded sand I Sands with Fines: More than 12% fines D Fines classify as ML or MH SM Silty sand G,H,I Fines Classify as CL or CH SC Clayey sand G,H,I Fine-Grained Soils: 50% or more passes the No. 200 sieve Silts and Clays: Liquid limit less than 50 Inorganic:PI > 7 and plots on or above “A” line J CL Lean clay K,L,M PI < 4 or plots below “A” line J ML Silt K,L,M Organic:Liquid limit - oven dried < 0.75 OL Organic clay K,L,M,N Liquid limit - not dried Organic silt K,L,M,O Silts and Clays: Liquid limit 50 or more Inorganic:PI plots on or above “A” line CH Fat clay K,L,M PI plots below “A” line MH Elastic Silt K,L,M Organic:Liquid limit - oven dried < 0.75 OH Organic clay K,L,M,P Liquid limit - not dried Organic silt K,L,M,Q Highly organic soils:Primarily organic matter, dark in color, and organic odor PT Peat A Based on the material passing the 3-in. (75-mm) sieve B If field sample contained cobbles or boulders, or both, add “with cobbles or boulders, or both” to group name. C Gravels with 5 to 12% fines require dual symbols: GW-GM well-graded gravel with silt, GW-GC well-graded gravel with clay, GP-GM poorly graded gravel with silt, GP-GC poorly graded gravel with clay. D Sands with 5 to 12% fines require dual symbols: SW-SM well-graded sand with silt, SW-SC well-graded sand with clay, SP-SM poorly graded sand with silt, SP-SC poorly graded sand with clay E Cu = D60/D10 Cc = 6010 2 30 DxD )(D F If soil contains ‡ 15% sand, add “with sand” to group name. G If fines classify as CL-ML, use dual symbol GC-GM, or SC-SM. H If fines are organic, add “with organic fines” to group name. I If soil contains ‡ 15% gravel, add “with gravel” to group name. J If Atterberg limits plot in shaded area, soil is a CL-ML, silty clay. K If soil contains 15 to 29% plus No. 200, add “with sand” or “with gravel,” whichever is predominant. L If soil contains ‡ 30% plus No. 200 predominantly sand, add “sandy” to group name. M If soil contains ‡ 30% plus No. 200, predominantly gravel, add “gravelly” to group name. N PI ‡ 4 and plots on or above “A” line. O PI < 4 or plots below “A” line. P PI plots on or above “A” line. Q PI plots below “A” line.