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ST1002-SY111214Geotechnical Engineering Report Main Street Development SWC of W. Bethel and S. Coppell Coppell, Texas December 14, 2011 Terracon Project No. 94115231 Prepared for: SCE Commercial Real Estate, LP Irving, Texas Prepared by: Terracon Consultants, Inc. Dallas, Texas TABLE OF CONTENTS Page 1.0INTRODUCTION ................................................................................................................. 1 2.0PROJECT INFORMATION ................................................................................................. 1 2.1Site Location and Description ..................................................................................... 1 2.2Project Description ..................................................................................................... 1 3.0SUBSURFACE CONDITIONS ............................................................................................ 2 3.1Typical Profile ............................................................................................................. 2 3.2Groundwater ............................................................................................................... 3 4.0RECOMMENDATIONS FOR DESIGN AND CONSTRUCTION ......................................... 4 4.1Geotechnical Considerations ...................................................................................... 4 4.2Earthwork ................................................................................................................... 5 4.2.1 Fill and Subgrade Preparation ....................................................................... 5 4.2.2 Select Fill ....................................................................................................... 5 4.2.3 Building Pad Preparation ............................................................................... 5 4.2.4 Compaction Requirements ............................................................................ 6 4.2.5 Drainage and Utilities .................................................................................... 6 4.3Monolithic, Post-Tensioned Slabs-on-Grade .............................................................. 7 4.4Auger Cast Piles ......................................................................................................... 8 4.4.1 Lateral Capacity ............................................................................................. 9 4.4.2 Auger Cast Piles Construction Considerations .............................................. 9 4.4.3 Grade Beams, Pier Caps and Wall Panels .................................................. 10 4.5Seismic Considerations ............................................................................................ 10 4.6Conventionally Reinforced Floor Systems ................................................................ 10 4.6.1 Structural Floor Slabs .................................................................................. 11 4.6.2 Floor Slabs/Flatwork on Prepared Subgrade .............................................. 11 4.7Pavements ................................................................................................................ 11 4.7.1 Pavement Subgrades .................................................................................. 11 4.7.2 Pavement Traffic ......................................................................................... 12 4.7.3 Pavement Sections ...................................................................................... 12 5.0GENERAL COMMENTS ................................................................................................... 13 APPENDIX A – FIELD EXPLORATION Exhibit A-1 Boring Location Plan Exhibit A-2 Field Exploration Description Exhibits A-3 through A-31 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 GEOTECHNICAL ENGINEERING REPORT MAIN STEET DEVELOPMENT Coppell, Texas Terracon Project No. 94115231 December 14, 2011 1.0 INTRODUCTION A multi-use development is planned at the intersection of W. Bethel and S. Coppell in Coppell, Texas. Our scope of services included drilling and sampling twenty-nine (29) borings to depths of 5 to 20 feet, laboratory testing, and engineering analyses. The purpose of these services is to provide information and geotechnical engineering recommendations relative to: subsurface soil conditions seismic considerations groundwater conditions floor slab design and construction earthwork pavement and associated drives foundation design and construction 2.0 PROJECT INFORMATION 2.1 Site Location and Description ItemDescription An approximate 22 acre tract at the in the southwest corner of West Location Bethel Road and South Coppell Road in Coppell, Texas Vacant site, currently under mass grading operations at the time of Existing conditions the geotechnical exploration Current ground cover Primarily bare ground Existing topography The site is relatively flat 2.2 Project Description ItemDescription Site layout See Appendix A, Exhibit A-1, Boring Location Plan. ResponsiveReliableResourceful 1 Geotechnical Engineering Report Coppell, Texas Main Street Development December 14, 2011 Terracon Project No. 94115231 ItemDescription Multi-use site with 13 office cottages, 11 retail/service buildings, 2 Planned construction restaurants, and 44 patio homes. Finished floor elevation Not known at this time, assumed to be ±2 feet of existing grades Columns: 100 kips Assumed maximum loads Walls: 2 to 3 kips per linear foot Slabs: 150 psf max Columns: 1 inch Assumed maximum allowable Walls: 1 inch vertical movement Floor slab: 1 inch Site grading Not known at this time Cut and fill slopes: 4H: 1V (Horizontal to vertical) max (recommended) 3.0 SUBSURFACE CONDITIONS 3.1 Typical Profile 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 boring locations can be found on the boring logs in Appendix A of this report. Based on the results of the borings, subsurface conditions on the project site can be generalized as follows: Approximate Depth to Stratum Materials Encountered (USCS symbol) Consistency Bottom of Stratum Fill materials consisting of crushed Very stiff to 1 1 to 8 feet, when encountered limestone base, and tan, brown, gray, and hard clays dark gray clays (CL and CH) 10 ½ to 20 feet. Borings B-3, B-9, Native soils consisting of tan, brown, light 2 and B-21 terminated in this gray, gray, and dark gray clays (CH) and Stiff to hard stratum at 5 to 20 feet sandy clays (CL) 14 to 20 feet. Borings B-1, B-2, B-6 through B-8, B-10 through Tan and light gray clayey sands (SC) and Loose to very 3 B-14, B-16 through B-20, and sands (SP) dense B-22 through B-29 terminated in this stratum at about 20 feet ResponsiveResourcefulReliable 2 Geotechnical Engineering Report Coppell, Texas Main Street Development December 14, 2011 Terracon Project No. 94115231 Approximate Depth to Stratum Materials Encountered (USCS symbol) Consistency Bottom of Stratum Termination depth of 20 feet in Stiff to very 4Tan and light gray clays (CH and CL) Borings B-5 and B-15 stiff 3.2 Groundwater The borings were advanced in the dry using auger drilling techniques, which allows short-term groundwater observations to be made while drilling. Groundwater seepage was encountered in some of the borings. The following table presents the groundwater observations at the time of the geotechnical exploration. Groundwater was not encountered in the remaining borings at that time. Depth to groundwater Depth to groundwater Boring following the completion observed while drilling of drilling B-2 12 feet 15 feet B-8 17 feet 19 feet B-11 18 feet 19 feet B-12 18.5 feet 19 feet B-13 18 feet Not encountered B-14 18 feet 19 feet B-15 18 feet 18 feet B-16 16.5 feet 17 feet B-17 18 feet 19 feet B-18 17 feet 16 feet B-19 19 feet 19 feet B-22 18.5 feet 19 feet B-23 19 feet 19 feet B-24 17 feet 18 feet B-25 17 feet 19 feet B-27 12 feet 14 feet B-29 18 feet Not encountered Groundwater conditions may be different at the time of construction. Groundwater conditions may change because of seasonal variations in rainfall and landscape irrigation. ResponsiveResourcefulReliable 3 Geotechnical Engineering Report Coppell, Texas Main Street Development December 14, 2011 Terracon Project No. 94115231 4.0 RECOMMENDATIONS FOR DESIGN AND CONSTRUCTION 4.1 Geotechnical Considerations The soils at this site consist of highly expansive clays overlying sands at varying depths. Due to the expansive nature of these clays, structures supported by shallow spread footings could be subject to excessive movements. Furthermore, the presence of the sandy soils and groundwater below about 11 feet in most borings would preclude the installation of a deeper foundation system such as underreamed shafts. Lightly loaded structures can be supported on a monolithic, post- tensioned foundation system. Greater column loads can be supported by installation of auger cast piles. A more refined selection of foundation types may be improved by the addition of a few deeper borings in the areas of greater column loads. Heavier loads could ideally be supported by drilled shafts bearing in the primary bedrock unit, which may be as deep as 30 to 40 feet on this site. The clay soils at this site are considered active to highly active with respect to moisture-induced volume changes (expansion or contraction). If floor slab movements must be limited to less than 1 inch, a floor system structurally supported above the subgrade is recommended. If potential slab movements on the order of 1 inch are acceptable for at-grade slabs, the floor slab can be supported on a modified subgrade. It should be noted that there is a risk that even ½ inch of movement can result in unsatisfactory performance. Some of the risks that can affect performance include uneven floors, floor and wall cracking, and sticking doors. Fill soils were encountered at the surface in several borings. In the absence of documented density control, the possibility of under-compacted zones or voids exists in these fills. Removal and replacement of all the fills following the recommendations in subsequent sections of this report is the only method of eliminating the risk of unusual settlement. Asphaltic concrete pavement or portland cement concrete pavement can be used at this site. If asphaltic concrete is used, the subgrade should be stabilized with lime. These pavements are not equal in performance. The portland cement concrete pavement is expected to require less maintenance. Geotechnical recommendations for building foundations, floor slab subgrade preparation, below grade construction, pavement, and earthwork are presented in the following report sections. ResponsiveResourcefulReliable 4 Geotechnical Engineering Report Coppell, Texas Main Street Development December 14, 2011 Terracon Project No. 94115231 4.2 Earthwork 4.2.1 Fill and Subgrade Preparation The on-site soils, free of vegetation, debris, and rocks greater than 4 inches in maximum dimension, are generally suitable for site grading. If imported fill materials are used, they should be clean soil with a Liquid Limit preferably less than 40 percent and no rock greater than 4 inches in maximum dimension. Prior to placing any fill, the areas to receive fill will need to be stripped and grubbed. Any subgrade areas to receive fill should be proofrolled with heavy pneumatic equipment. Any soft or pumping areas identified should be excavated to firm ground and properly backfilled. 4.2.2 Select Fill The material used as select fill should be sandy clay to clayey sand with a Liquid Limit (LL) of less than 35 percent and a Plasticity Index (PI) preferably between 6 and 15. The first lift of select fill should be placed wet of optimum to prevent drying the underlying subgrade. Positive drainage must be provided away from the structure to prevent the ponding of water in the select fill. As an alternate to select fill, flexible base can be used. The base should meet the requirements of TxDOT Item 247, Type A, Grade 1 or 2. Recycled concrete meeting these requirements is acceptable. The use of flexible base rather than low plasticity select fill is recommended in below grade areas to provide for a more stable working surface. 4.2.3 Building Pad Preparation The potential magnitude of the moisture induced movements is rather indeterminate. It is influenced by the soil properties, overburden pressures, and to a great extent by soil moisture levels at the time of construction. Based on the soil types encountered in the borings, movements in slabs-on-grade placed near existing grades are estimated to be about 3 to 4 inches. For the construction of monolithic, post-tensioned slab foundations, some degree of earthwork may Section 4.3 be recommended to reduce the design parameters provided in . For these cases, the recommended depths of subgrade preparation are listed alongside the corresponding PTI design parameters. For these cases, the upper 1 foot of soils should also consist of select fill. In conjunction with auger cast piles, interior slabs can be placed on a modified subgrade. The building pad, sensitive flatwork areas, and one foot beyond should be excavated to permit installation of modified soils. In order to achieve slab-on-grade movements of about 1 inch, we recommend overexcavating to a depth of 10 feet below finished floor elevation and then placing moisture conditioned site soils in conjunction with the upper one foot of select fill to reestablish grade. ResponsiveResourcefulReliable 5 Geotechnical Engineering Report Coppell, Texas Main Street Development December 14, 2011 Terracon Project No. 94115231 In some instances it is considered advantageous to cap the moisture-conditioned pad with a lime stabilized layer, rather than select fill. This provides a more all weather surface for construction, and is often considered an economic advantage. The lime-stabilized section should be 6 inches Section 4.7.1 deep and follow the TxDOT specifications referenced in of this report. The select fill or lime cap and moisture conditioning processes should be extended beyond the building line to include entrances, the canopy slab, abutting sidewalks, and other flatwork areas sensitive to movement. 4.2.4 Compaction Requirements Recommendations for compaction are presented in the following table.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. ITEMDESCRIPTION Subgrade preparation to Surface scarified to a minimum depth of 6 inches receive fill Site soil and select fill 9-inches or less loose lift thickness Lift thickness A minimum of 95% maximum standard Proctor dry density (ASTM D General site fills 698) placed at or above optimum moisture content Moisture conditioned clays 92% to 98% standard Proctor dry density (ASTM D 698) placed at beneath building pads least +4 percentage points above optimum moisture content A minimum of 95% maximum standard Proctor dry density (ASTM D Select fill/flexible base 698) at -2 to +2 percentage points of optimum moisture content Lime-stabilized or untreated A minimum of 95% maximum standard Proctor dry density (ASTM D pavement subgrade soils 698) at -1 to +3 percentage points of optimum moisture content 4.2.5 Drainage and Utilities The flatwork abutting the structure should be sloped down to provide effective drainage away from the building. Where paving or flatwork abuts the structure, the joints should be properly sealed and maintained to prevent the infiltration of surface water. Open ground should be sloped on 5 percent or steeper grades for 10 or more feet away from the building. Roof drains should discharge on paved surface or be extended away from the structure. The on-site soils are susceptible to erosion and will require protection. Care should be taken that utility trenches are properly backfilled. Backfilling should be accomplished with properly compacted on-site soils. A minimum 3-foot wide, properly compacted ResponsiveResourcefulReliable 6 Geotechnical Engineering Report Coppell, Texas Main Street Development December 14, 2011 Terracon Project No. 94115231 clay plug at the building line is recommended to help prevent water from migrating under the building through the utility trench backfill. 4.3 Monolithic, Post-Tensioned Slabs-on-Grade Post-tensioned or conventionally reinforced monolithic, slab-on-grade foundation systems used on this site must be designed to resist potential movements due to volume changes in the soil without inducing unacceptable distress in the foundation, structural elements or architectural finishes. The movements will typically tend to occur differentially between more heavily loaded perimeter grade beams and lightly loaded interior portions of the slab-on-grade system. Design parameters are presented in the table below using the Post-Tensioning Institute's (PTI) slab-on-grade design method (Third Edition, 2004). Design parameters provided are for slabs placed on the existing soils and a modified subgrade. Center Lift Edge Lift Subgrade Treatment eyey mmmm feet inchfeet inch None; existing site soils 6.7 2.3 4.1 3.9 Overexcavating to a depth of 4 feet, and reestablishing grade with moisture conditioned 6.7 2.3 4.1 2.0 soils and a 1 foot cap of select fill Overexcavating to a depth of 10 feet, and reestablishing grade with moisture conditioned 6.7 2.3 4.1 1.4 soils and a 1 foot cap of select fill The grade beams of the slab-on-grade foundation system should exert a maximum bearing pressure of 1,800 psf. These beams should extend a minimum of 18 inches below finished grade and bear in native stiff clays, medium dense sands, or in properly compacted fill. Design parameters are estimates based on assumptions that the area around the structure will be well drained, landscape beds are not over watered, and utility leaks are promptly repaired. Trees should be planted at least one-mature tree height from the building. Root barriers should be installed if trees are planted within one mature tree height. It should be noted that excessive water from any source could result in movements greater than the slab was designed to accommodate. A greater risk of unsatisfactory foundation performance exists with a slab-on-grade design than a drilled shaft foundation system. For example, should leaks develop in underground water or sewer lines, or the grades around the building are changed and cause ponding of water, unacceptable slab movements could develop. If the risk of movement ResponsiveResourcefulReliable 7 Geotechnical Engineering Report Coppell, Texas Main Street Development December 14, 2011 Terracon Project No. 94115231 is unacceptable, the building should be designed with a structural slab and deep, drilled shaft foundations. 4.4 Auger Cast Piles Based on the conditions encountered in the borings, a system of auger cast piles bearing in the medium dense sands can be used to support loads. Augered cast-in-place piles are installed by advancing a hollow-stem auger to a predetermined depth in the ground, and then pumping high- strength flowable cement grout into the hole through the bottom of the hollow auger as the auger is slowly withdrawn. The grout is pumped under relatively high pressure, and a positive head of grout is maintained above the base of the auger during auger extraction. After the auger is completely removed, reinforcing steel is then placed. Full scale, on-site load tests are customarily performed on augered cast-in-place piles to verify that the desired capacity is achievable prior to continuing construction. Design recommendations are presented below. Design Parameter Recommendation Bearing stratum Medium dense sands Minimum pile diameter 18 inches Ultimate load capacity and settlement of the augered-cast piles should be verified using load tests procedures as described in ASTM D1143. Final design augered cast-in- Final design augered cast-in-place pile place pile capacities and settlements should be based upon capacities field load testing data. A safety factor of 2.0 (allowable capacity reduction) is recommended for augered cast-in- place pile after ultimate capacity is determined by the load test (ASTM D1143). A center to center spacing of 3 pile diameters is Minimum center to center spacing of recommended between adjacent piles. Closely spaced piles adjacent piles should be examined on a case by case basis. Settlements of properly installed augered cast-in-place piles Total and differential settlement are expected to be less than 1 inch. Most of this settlement is expected to occur as the foundation loads are applied. It is anticipated that an allowable design compressive capacity of about 50 kips will be supported by load test on an 18 inch diameter shaft embedded to a depth of 20 feet, or a 24 inch diameter shaft embedded to 20 feet can support up to 70 kips. A safety factor of 2 has been applied to the preliminary allowable capacities. ResponsiveResourcefulReliable 8 Geotechnical Engineering Report Coppell, Texas Main Street Development December 14, 2011 Terracon Project No. 94115231 Auger-cast piles may be subject to some vertical movement due to the expansive nature of the soils at the site. Embedment depths for vertical capacities are not likely to provide for sufficient anchorage against pullout. We estimate that upward shaft movement be about ½ inch or less. 4.4.1 Lateral Capacity The piles may be subject to lateral loads. Recommendations for design of laterally loaded piles are presented in the table. This value recommended below may be increased by 20 percent when considering wind loads. The passive resistance should be applied to the projected diameter of the pile. Soil Allowable Passive Resistance Site clays (0-11 feet) 200 psf Sands (below 11 feet) 500 psf These recommended lateral earth pressures apply to shafts spaced at 5 or more shaft diameters, center to center, in the direction parallel to loading. This office should review the lateral earth pressure recommendations for shafts spaced closer than 5 shaft diameters. 4.4.2 Auger Cast Piles Construction Considerations Augered cast-in-place piles shall be made by rotating a continuous flight, hollow-shaft auger into the ground to design depth. High strength grout is injected through the auger shaft in such a way as to exert positive upward grout pressure on the auger flights and positive lateral earth pressure on the shaft walls, as the auger is being withdrawn. Grout used for the augered-cast piles should have a flow rate of 10 to 25 seconds when a ¾ inch opening (Modified U.S. Army Corps of Engineers) flow cone is used. A minimum of two piles should be tested prior to commencement of foundation construction using the ASTM D1143 axial pile load test procedure. The pile should be loaded until failure or at least two times the design load. Test piles loaded to failure should not become part of the permanent foundation system. Load testing should be performed by the augered-cast pile contractor in the presence of the geotechnical engineer of record and/or his designee. Cost of the load tests performed by the piling contractor should be included in the base bid price. We recommend that Terracon be retained to observe and document the augered-cast pile construction. The geotechnical engineer or his representative should document the shaft diameter, drilling elevation, tip elevation, elevation of butt, quantity of grout placed, reinforcement steel, plumbness, and the minimum penetration into the bearing soils. Significant deviations from the specified or anticipated conditions should be reported to the owner’s representative and the structural engineer. ResponsiveResourcefulReliable 9 Geotechnical Engineering Report Coppell, Texas Main Street Development December 14, 2011 Terracon Project No. 94115231 4.4.3 Grade Beams, Pier Caps and Wall Panels In conjunction with auger-cast piles, all grade beams or wall panels should be supported by the drilled shafts. A minimum void space of 8 inches is recommended between the bottom of grade beams, pier cap extensions, or wall panels and the subgrade. This void will serve to minimize distress resulting from swell pressures generated by the clay soils. Structural cardboard forms are one acceptable means of providing this void beneath cast-in-place elements. Soil retainers should be used to prevent infilling of the void. The grade beams should be formed rather than cast against earth trenches. Backfill against the exterior face of grade beams, wall panels and pier caps should be on site clay soils placed and Section 4.2.4 compacted as described in . 4.5 Seismic Considerations Code Used Site Classification 12 2009 International Building Code (IBC) D 1. In general accordance with the 2009 International Building Code, Table 1613.5.2. 2. The 2009 International Building Code (IBC) requires a site soil profile determination extending a depth of 100 feet for seismic site classification. The current scope requested does not include the required 100 foot soil profile determination. Borings were extended to a maximum depth of approximately 20 feet and this seismic site class definition considers that stiff soils exist\s below the maximum depth of the subsurface exploration. 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. 4.6 Conventionally Reinforced Floor Systems Lightly loaded floor slabs placed on-grade will be subject to movement as a result of moisture induced volume changes in the active soils. The soils expand (heave) with increases in moisture and contract (shrink) with decreases in moisture. The movement typically occurs as post construction heave. The potential magnitude of the moisture induced movements is rather indeterminate. It is influenced by the soil properties, overburden pressures, and to a great extent by soil moisture levels at the time of construction. Based on the soil types encountered in the borings, movements in slabs-on-grade placed near existing grades are estimated to be about 3 to 4 inches. Note that movements of ½ inch can result in uneven floors, sticking doors, and cracking of floor slabs and wall partitions. If the risk of these movements is unacceptable, the floor slab should be structural. ResponsiveResourcefulReliable 10 Geotechnical Engineering Report Coppell, Texas Main Street Development December 14, 2011 Terracon Project No. 94115231 4.6.1 Structural Floor Slabs The building floor slab should be structurally supported above the subgrade if movements are to be limited to less than 1 inch. A minimum void space of 12 inches is recommended beneath the slab. The minimum void space can be provided by the use of cardboard carton forms, or a deeper crawl space. The bottom of the void should preferably be higher than adjacent exterior grades. A ventilated and drained crawl space is preferred under the building for several reasons, including the following: Ground movements will affect the project utilities, which can cause breaks in the lines and distress to interior fixtures. A crawl space permits utilities to be hung from the superstructure, which greatly reduces the possibility of distress due to ground movements. It also can provide ready access in the event repairs are necessary. Ground movements are uneven. A crawl space can be positively drained preventing the ponding of water and reducing the possibility of distress due to unexpected ground movements. 4.6.2 Floor Slabs/Flatwork on Prepared Subgrade Slab on-grade construction should only be considered if slab movements on the order of about 1 inch are considered acceptable. Reductions in anticipated movements can be achieved by using methods developed in this area to reduce on-grade slab movements. These methods include excavating and moisture conditioning the site soils and capping them with non-expansive select Section 4.2.3 fills. Recommendations are presented in for the treatment of these soils to achieve slab movements on the order of about 1 inch. The use of a vapor retarder should be considered beneath concrete slabs on grade that will be covered with wood, tile, or carpet. A vapor retarder should be used for other moisture sensitive coverings, impervious coverings, or when the slab will support equipment sensitive to moisture. When conditions warrant the use of a vapor retarder, the slab designer and slab contractor should refer to ACI 302 and/or ACI 360 for procedures and cautions regarding the use and placement of a vapor retarder. 4.7 Pavements 4.7.1 Pavement Subgrades Subgrade materials at this site will consist of clay soils. These soils are subject to loss of support with the moisture increases that can occur beneath paving. The clay soils react with hydrated lime, which serves to improve and maintain their support value. Lime stabilization is recommended ResponsiveResourcefulReliable 11 Geotechnical Engineering Report Coppell, Texas Main Street Development December 14, 2011 Terracon Project No. 94115231 beneath flexible (asphalt) pavement sections. Rigid (concrete) pavements may be placed on compacted subgrade without lime treatment. For budgeting purposes, 7 percent hydrated lime (TxDOT Item 264), by dry weight, can be used for treating the subgrade beneath flexible pavements. The lime application rate should be determined by laboratory testing once the pavement subgrade is rough graded. The lime should be thoroughly mixed and blended with the top 6 inches of the subgrade (TxDOT, Item 260). Stabilization should extend a minimum of one foot beyond the edge of the pavement. The lime stabilized or natural subgrade should then be uniformly compacted in accordance to the Section 4.2.4 recommendations in . It should then be protected and maintained in a moist condition until the pavement is placed. Pavement subgrades should be graded to prevent ponding and infiltration of excessive moisture on or adjacent to the pavement subgrade surface. Site grading is generally accomplished early in the construction phase. However as construction proceeds, the subgrade may be disturbed due to utility excavations, construction traffic, desiccation, or rainfall. As a result, the pavement subgrade may not be suitable for pavement construction and corrective action will be required. The subgrade should be carefully evaluated at the time of pavement construction for signs of disturbance or excessive rutting. If disturbance has occurred, pavement subgrade areas should be reworked, moisture conditioned, and properly compacted to the recommendations in this report immediately prior to paving. 4.7.2 Pavement Traffic Traffic patterns and anticipated loading conditions were not available; however, typical pavement sections with subgrade stabilization alternatives for a 20 year design life are provided. These represent a total of 45,000 18-Kip Equivalent Single Axle Loads (ESALs) for Light Duty pavement and 100,000 18-Kip ESALs for the Medium Duty pavement. The Light Duty pavement is intended for passenger car and pick up trucks. The Medium Duty pavement is intended for passenger car, pickup trucks, small delivery trucks, fire lanes and tractor trailer trucks. If the pavements are subject to heavier loading and higher traffic counts than the assumed values, this office should be notified and provided with the information so that we may review these pavement sections and make revisions if necessary. 4.7.3 Pavement Sections Both asphalt and concrete pavement sections are presented in the following table. They are not considered equal. Over the life of the pavement, concrete sections would be expected to require less maintenance. ResponsiveResourcefulReliable 12 Geotechnical Engineering Report Coppell, Texas Main Street Development December 14, 2011 Terracon Project No. 94115231 Pavement Thickness, Inches Pavement Section Light Duty Medium Duty Dumpster Apron 45,000 x 18-kip ESALs100,000 x 18-kip ESALs Concrete 5 6 7 Portland Cement Compacted 6 6 6 Concrete Subgrade TxDOT Type D TxDOT Item 340 2 2 NA Asphaltic Concrete Full Depth Type A or B Asphaltic TxDOT Item 340 3 4 NA Concrete Asphaltic Concrete TxDOT, Item 260 Lime Stabilized 6 6 NA Subgrade * All materials should meet the TxDOT Standard Specifications for Highway Construction. The concrete should have a minimum 28-day compressive strength of 3,000 psi in light duty areas and 3,500 psi in medium duty and dumpster areas. It should contain a minimum of 5 ±1.5 percent entrained air. As a minimum, the section should be reinforced with No. 3 bars on 18-inch centers in both directions. Pavements will be subject to differential movement due to heave in the site soils. Flat grades should be avoided with positive drainage provided away from the pavement edges. Backfilling of curbs should be accomplished as soon as practical to prevent ponding of water. Openings in pavement, such as landscape islands, are sources for water infiltration into surrounding pavements. Water collects in the islands and migrates into the surrounding subgrade soils thereby degrading support of the pavement. This is especially applicable for islands with raised concrete curbs, irrigated foliage, and low permeability near-surface soils. The civil design for the pavements with these conditions should include features to restrict or to collect and discharge excess water from the islands. Examples of features are edge drains connected to the storm water collection system or other suitable outlet and impermeable barriers preventing lateral migration of water such as a cutoff wall installed to a depth below the pavement structure. 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. ResponsiveResourcefulReliable 13 Geotechnical Engineering Report Coppell, Texas Main Street Development December 14, 2011 Terracon Project No. 94115231 The analysis and recommendations presented in this report are based upon the data obtained from the borings performed at the indicated locations and from other information discussed in this report. This report does not reflect variations that may occur between borings, across the site, or due to the modifying effects of weather. The nature and extent of such variations may not become evident until during or after construction. If variations appear, we should be immediately notified so that further evaluation and supplemental recommendations can be provided. The scope of services for this project does not include either specifically or by implication any environmental or biological (e.g., mold, fungi, bacteria) assessment of the site or identification or prevention of pollutants, hazardous materials or conditions. If the owner is concerned about the potential for such contamination or pollution, other studies should be undertaken. This report has been prepared for the exclusive use of our client for specific application to the project discussed and has been prepared in accordance with generally accepted geotechnical engineering practices. No warranties, either express or implied, are intended or made. Site safety, excavation support, and dewatering requirements are the responsibility of others. In the event that changes in the nature, design, or location of the project as outlined in this report are planned, the conclusions and recommendations contained in this report shall not be considered valid unless Terracon reviews the changes and either verifies or modifies the conclusions of this report in writing. ResponsiveResourcefulReliable 14 APPENDIX A FIELD EXPLORATION Geotechnical Engineering Report Coppell, Texas Main Street Development December 14, 2011 Terracon Project No. 94115231 Field Exploration Description Subsurface conditions were explored by drilling twenty-nine borings at the approximate locations indicated on the Boring Location Plan on Exhibit A-1 in Appendix A. The field exploration was performed on November 15 through 18, 2011. The test locations were established in the field by measuring from available reference features and estimating right angles. The boring locations should be considered accurate only to the degree implied by the methods employed to determine them. The borings were performed using a truck-mounted drill rig. Hollow stem augers were used to advance the borings. Samples of the soils encountered in the borings were obtained using thin- walled tube sampling procedures and split-barrel samplers in conjunction with the Standard Penetration Test. The samples were tagged for identification, sealed to reduce moisture loss, and taken to the laboratory for further examination, testing, and classification. 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. Boring logs are presented on Exhibit A-3 through A-31 in Appendix A. General notes to log terms and symbols are presented on Exhibit C-1 in Appendix C. Exhibit A-2 APPENDIX B LABORATORY TESTING Geotechnical Engineering Report Coppell, Texas Main Street Development December 14, 2011 Terracon Project No. 94115231 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, particle size analyses, and moisture content measurements were made 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. Absorption swell tests were performed on selected samples of the cohesive materials. These tests were used to quantitatively evaluate volume change potential at in-situ moisture levels. Strength of cohesive soils was measured by hand penetrometer and unconfined compression tests. The results of the swell tests are presented in the following table. The results of the other laboratory tests are presented on the Boring Logs in Appendix A. LiquidPlasticityInitialFinal Boring Depth Surcharge Swell LimitIndexMoisture Moisture No. (feet) (psf) (%) (%) (%) (%) (%) B-1 8 – 10 67 41 18.4 21.0 1,250 2.8 B-7 8 – 10 45 23 13.6 18.8 1,250 0.8 B-8 6 – 8 62 34 20.6 24.4 875 3.1 B-10 8 – 10 59 36 16.0 19.8 1,250 2.5 B-11 8 – 10 70 44 20.2 24.3 1,250 3.4 B-12 6 – 8 53 27 15.7 19.0 875 1.5 B-13 8 – 10 63 38 21.0 25.3 1,250 1.8 B-19 8 – 10 72 45 22.0 25.7 1,250 1.8 B-22 8 – 10 64 38 19.5 27.2 1,250 2.6 B-26 6 – 8 60 35 21.9 24.1 875 1.4 B-28 8 – 10 61 37 17.7 23.9 1,250 1.7 Exhibit B-1 APPENDIX C SUPPORTING DOCUMENTS GENERAL NOTES DRILLING & SAMPLING SYMBOLS: 3 SS: Split Spoon – 1-/" I.D., 2" O.D., unless otherwise noted HS: Hollow Stem Auger 8 ST: Thin-Walled Tube - 2" O.D., unless otherwise noted PA: Power Auger TC: TxDOT Cone Penetrometer Test HA: Hand Auger DB: Diamond Bit Coring - 4", N, B RB: Rock Bit BS: Bulk Sample or Auger Sample WB: Wash Boring or Mud Rotary The number of blows required to advance a standard 2-inch O.D. split-spoon sampler (SS) the last 12 inches of the total 18-inch penetration with a 140-pound hammer falling 30 inches is considered the “Standard Penetration” or “N-value”. For TxDOT cone penetrometer (TC) the penetration value is reported as the number of blows required to advance the sampler 12 inches or penetration in inches after 100 blows using a 170-pound hammer falling 24 inches, reported as “blows per foot” or inches per 100 blows, and is not considered equivalent to the “Standard Penetration” or “N-value”. WATER LEVEL MEASUREMENT SYMBOLS: WL: Water Level WS: While Sampling N/E: Not Encountered WCI: Wet Cave in WD: While Drilling DCI: Dry Cave in BCR: Before Casing Removal AB: After Boring ACR: After Casing Removal Water levels indicated on the boring logs are the levels measured in the borings at the times indicated. Groundwater levels at other times and other locations across the site could vary. In pervious soils, the indicated levels may reflect the location of groundwater. In low permeability soils, the accurate determination of groundwater levels may not be possible with only short-term observations. DESCRIPTIVE SOIL CLASSIFICATION: Soil classification is based on the Unified Classification System. Coarse Grained Soils havemore 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. CONSISTENCY OF FINE-GRAINED SOILSRELATIVE DENSITY OF COARSE-GRAINED SOILS Unconfined Standard Penetration Standard Penetration TxDOT Cone Compressive or N-value (SS)Consistencyor N-value (SS)Penetrometer (TC) Relative Density Blows/Ft.Blows/Ft.Blows/Ft. Strength, Qu, psf < 5000 - 1 Very Soft 0 – 3 0-8 Very Loose 500 – 1,000 2 - 4 Soft 4 – 9 8-20 Loose 1,001 – 2,000 4 - 8 Medium Stiff 10 – 29 20-80 Medium Dense 2,001 – 4,000 8 -15 Stiff 30 – 49 80-5”/100 Dense 4,001 – 8,000 15 - 30 Very Stiff > 50 5”/100 to 0”/100 Very Dense 8,000+ > 30 Hard RELATIVE PROPORTIONS OF SAND AND GRAVELGRAIN SIZE TERMINOLOGY Descriptive Term(s) of other Percent oMajor Component f Particle Size ConstituentsDry Weightof Sample Trace< 15 Boulders Over 12 in. (300mm) With 15 – 29 Cobbles 12 in. to 3 in. (300mm to 75 mm) Modifier > 30 Gravel 3 in. to #4 sieve (75mm to 4.75 mm) Sand #4 to #200 sieve (4.75mm to 0.075mm) Silt or Clay Passing #200 Sieve (0.075mm) PLASTICITY DESCRIPTION RELATIVE PROPORTIONS OF FINES Descriptive Term(s) of other Percent o fPlasticity Term ConstituentsDry WeightIndex Trace < 5 Non-plastic 0 With 5 – 12 Low 1-10 Modifiers > 12 Medium 11-30 High 30+ Exhibit C-1 UNIFIED SOIL CLASSIFICATION SYSTEM Soil Classification A Criteria for Assigning Group Symbols and Group Names Using Laboratory Tests Group B Group Name Symbol F E Gravels: GW Well-graded gravel Cu 4 and 1 Cc 3 Clean Gravels: More than 50% of C F Less than 5% fines E GP Poorly graded gravel Cu 4 and/or 1 Cc 3 coarse F,G, H Fines classify as ML or MH GM Silty gravel Gravels with Fines: fraction retained on Coarse Grained Soils: C F,G,H More than 12% fines Fines classify as CL or CH GC Clayey gravel No. 4 sieve More than 50% retained I E SW Well-graded sand Cu 6 and 1 Cc 3 Clean Sands: Sands: on No. 200 sieve D Less than 5% fines I E Cu 6 and/or 1 Cc 3SP Poorly graded sand 50% or more of coarse fraction passes G,H,I Fines classify as ML or MH SM Silty sand Sands with Fines: No. 4 sieve D More than 12% fines G,H,I Fines Classify as CL or CH SC Clayey sand K,L,M J CL Lean clay PI 7 and plots on or above “A” line Inorganic: K,L,M J ML Silt PI 4 or plots below “A” line Silts and Clays: Liquid limit less than 50 K,L,M,N Liquid limit - oven dried Organic clay Organic: OL 0.75 Fine-Grained Soils: K,L,M,O Liquid limit - not dried Organic silt 50% or more passes the K,L,M PI plots on or above “A” line CH Fat clay No. 200 sieve Inorganic: K,L,M PI plots below “A” line MH Elastic Silt Silts and Clays: Liquid limit 50 or more K,L,M,P Liquid limit - oven dried Organic clay Organic: OH 0.75 K,L,M,Q Liquid limit - not dried Organic silt Highly organic soils: Primarily organic matter, dark in color, and organic odor PT Peat AH Based on the material passing the 3-in. (75-mm) sieve If fines are organic, add “with organic fines” to group name. B I If field sample contained cobbles or boulders, or both, add “with cobbles If soil contains 15% gravel, add “with gravel” to group name. J or boulders, or both” to group name. If Atterberg limits plot in shaded area, soil is a CL-ML, silty clay. C K Gravels with 5 to 12% fines require dual symbols: GW-GM well-graded If soil contains 15 to 29% plus No. 200, add “with sand” or “with gravel with silt, GW-GC well-graded gravel with clay, GP-GM poorly gravel,” whichever is predominant. graded gravel with silt, GP-GC poorly graded gravel with clay. L If soil contains 30% plus No. 200 predominantly sand, add “sandy” D Sands with 5 to 12% fines require dual symbols: SW-SM well-graded to group name. sand with silt, SW-SC well-graded sand with clay, SP-SM poorly graded M If soil contains 30% plus No. 200, predominantly gravel, add sand with silt, SP-SC poorly graded sand with clay “gravelly” to group name. N PI 4 and plots on or above “A” line. 2 30 O E (D)PI 4 or plots below “A” line. Cu = D/D Cc = 6010 P PI plots on or above “A” line. 1060 DxD Q PI plots below “A” line. 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. Exhibit C-2