SOIL DATA: Centennial Montessori. in McKinney, TX

Transcription

1 SOIL DATA: Centennial Montessori in McKinney, TX

2 REPORT OF SUBSURFACE EXPLORATION AND GEOTECHNICAL ENGINEERING SERVICES CENTENNIAL MONTESSORI ACADEMY ELDORADO PARKWAY AT ALMA ROAD MCKINNEY, TEXAS FOR CENTENNIAL MONTESSORI ACADEMY, LLC OCTOBER 24, 2007

3 GEOTECHNICAL CONSTRUCTION MATERIALS ENVIRONMENTAL October 24, 2007 Mr. Brad Chatterjee LLC 2840 Keller Springs Road, Suite 801 Carrollton, Texas ECS Project No. 19:5312 Reference: Report of Subsurface Exploration and Geotechnical Engineering Services Eldorado Parkway at Alma Road Dear Mr. Chatterjee: ECS Texas, LLP (ECS) has completed the subsurface exploration for the proposed building at the referenced site in. The enclosed report describes the subsurface exploration procedures, laboratory testing, and geotechnical recommendations for development of the site. A Boring Location Diagram is included in the Appendix of this report along with the Boring Logs performed for the exploration. We appreciate this opportunity to be of service to you during the design phase of this project. If you have any questions with regard to the information and recommendations presented in this report, or if we can be of further assistance to you in any way during the planning or construction of this project, please do not hesitate to contact us at (972) Respectfully, ECS Texas, LLP David A. Lewis, P.E. Senior Geotechnical Engineer Syed K. Haneefuddin, P.E. Principal Engineer The seal appearing on this document was authorized by Syed Khaja Haneefuddin, P.E on October 24, pc: Encl. 2pc: GHLA 4950 Keller Springs Road, Suite 480, Addison, TX PH (972) FX (972)

4 REPORT PROJECT Subsurface Exploration and Geotechnical Engineering Services Eldorado Parkway at Alma Road CLIENT, LLC 2840 Keller Springs Road Suite 801 Carrollton, Texas SUBMITTED BY ECS Texas, LLP 4950 Keller Springs Road Suite 480 Addison, Texas PROJECT #19:5312 DATE October 24, 2007

5 TABLE OF CONTENTS PAGE PROJECT OVERVIEW 1 Introduction 1 Scope of Work 1 Proposed Construction 1 Purposes of Exploration 1 EXPLORATION PROCEDURES 2 Subsurface Exploration Procedures 2 Laboratory Testing Program 2 EXPLORATION RESULTS 3 Site Conditions 3 Subsurface Conditions 3 Groundwater Observations 4 ANALYSIS AND RECOMMENDATIONS 4 Earthwork Operations 4 Building Pad Preparation 5 Foundation Recommendations 7 Straight-Sided Drilled Shaft Foundation 7 Construction Considerations - Drilled Shafts 8 Grade Beams - Drilled Shafts 8 Monolithic Slab Foundation 9 Pavement Subgrade 11 Pavement Sections 11 Seismic Site Class Determination 13 Drainage 13 Closing 13 APPENDIX 15

6 ECS Project No. 19:5312 PROJECT OVERVIEW Introduction This report presents the results of our subsurface exploration and geotechnical engineering recommendations for the proposed building located in. The Boring Location Diagram included in the Appendix of this report shows the approximate location of this project. Scope of Work The conclusions and recommendations contained in this report are based on six soil borings sampled in the vicinity of the proposed building and parking areas. Borings B-1 through B-3 were drilled to a depth of about 25 feet below existing grade in the proposed building footprint. Borings B-4 through B-6 were drilled to a depth of about 5 feet below existing grade in the proposed pavement areas. Results of the soil borings, along with a Boring Location Diagram showing the approximate boring locations, are included in the Appendix of this report. This report presents our recommended geotechnical design parameters for project foundation design. In addition, the report provides construction considerations based upon the results of the soil borings and our previous experience in this area. Recommendations for site grading and area paving are also provided. Proposed Construction According to the information provided, we understand the project consists of constructing a single story building with a footprint area of approximately 8,815 square feet. Associated paved parking areas and drive lanes are also planned for the site. Site grading information was not available at the time of this report. However, it is anticipated that finished grade for the new structure will be within about 1½ feet of existing grade. Purposes of Exploration The purposes of this exploration were to explore the soil and groundwater conditions at the site and to develop engineering recommendations to guide design and construction of the project. We accomplished these purposes by: 1. Drilling six borings in the vicinity of the proposed building and pavement areas to depths of about 5 and 25 feet below existing grade to explore the subsurface soil and groundwater conditions. 1

7 ECS Project No. 19: Performing laboratory tests on selected representative soil samples from the borings to evaluate pertinent engineering properties. 3. Analyzing the field and laboratory data to develop appropriate engineering recommendations. Subsurface Exploration Procedures EXPLORATION PROCEDURES The soil borings were located in the field by a representative of ECS using taping procedures based on landmarks shown on the site plan provided by the client. The soil borings were performed with a truck-mounted rotary-type auger drill rig that utilized continuous flight augers to advance the boreholes. Representative samples were obtained using thin-walled tube sampling procedures in general accordance with ASTM Specification D In the thin-walled tube sampling procedure, a thin-walled seamless steel tube with a sharp cutting edge is pushed hydraulically into the ground to obtain relatively undisturbed samples of cohesive or moderately cohesive soils. Texas cone penetrometer tests were performed to evaluate the load carrying capacity of the limestone encountered. These tests were performed in general accordance with test method Tex- 132-E in the Texas Department of Transportation (TxDOT) Manual of Testing Procedures. The results of these tests are shown on the attached boring logs at the depths of occurrence. Field logs of the soils encountered in the borings were maintained by the drill crew. After recovery, each geotechnical soil sample was removed from the sampler and visually classified. Representative portions of each soil sample were then wrapped in plastic and transported to our laboratory for further visual examination and laboratory testing. After completion of the drilling operations, the boreholes were backfilled with auger cuttings to the existing ground surface. Laboratory Testing Program Representative soil samples were selected and tested in our laboratory. The soil samples were tested for moisture content, Atterberg Limits, swell potential, dry density, and unconfined compressive strength. A calibrated hand penetrometer was also used to estimate the unconfined compressive strength of several of the soil samples. The calibrated hand penetrometer has been correlated with unconfined compression tests and provides a better estimate of the soil consistency than visual observation alone. These test results are provided on the attached boring logs in the Appendix. 2

8 ECS Project No. 19:5312 An experienced geotechnical engineer classified each soil sample on the basis of texture and plasticity in general accordance with the Unified Soil Classification System. The group symbols for each soil type are indicated in parentheses following the soil descriptions on the boring logs. A brief explanation of the Unified System is included with this report. The geotechnical engineer grouped the various soil types into the major zones noted on the boring logs. The stratification lines designating the interfaces between earth materials on the boring logs and profiles are approximate; in situ, the transitions may be gradual. The soil samples will be retained in our laboratory for a period of 60 days, after which, they will be discarded unless other instructions are received as to their disposition. Site Conditions EXPLORATION RESULTS The site of this investigation is located at the northwest corner of the intersection of Eldorado Parkway and Alma Road in. At the time of this investigation, the site was covered with light vegetation. Based on visual observations, the surface topography was relatively level. Subsurface Conditions The boring locations were selected to explore the proposed building and parking/drive areas. The general soil conditions encountered at the boring locations can be summarized as follows. Stratum I consists of very stiff to hard dark gray CLAY (CH). This stratum was encountered at the ground surface and extended to depths ranging from about 2 to 6 feet below existing grade. The Stratum I clay is highly plastic and susceptible to moisture induced volumetric changes. Stratum II consists of hard, dark grayish brown and grayish brown CLAY (CH). This stratum was encountered below Stratum I and extended to depths ranging from about 6 to 8 feet below existing grade. This stratum is considered highly plastic and is also susceptible to moisture induced volumetric changes. Stratum III consists of hard, tan and gray CLAY (CH) with calcareous deposits. This stratum was encountered below Stratum II and extended to depths of 12 feet below existing grade. This stratum is considered highly plastic and is also susceptible to moisture induced volumetric changes. Stratum IV consists of tan weathered limestone. This stratum was encountered below Stratum III and extended to depths of 17 feet below existing grade. 3

9 ECS Project No. 19:5312 Stratum V consists of gray limestone. This stratum was encountered below Stratum IV and extended to the 25-foot boring termination depth. Refer to the attached boring logs for a more detailed description of the subsurface conditions encountered in the borings. The specific soil types observed at the borings are noted on the boring logs, enclosed in the Appendix. Groundwater Observations The borings were monitored while drilling and after completion of drilling for the presence and level of groundwater. Groundwater seepage was not observed while advancing or at the completion of drilling the borings. Although seepage was not encountered in the borings during our drilling, water can be encountered in the natural joints and fissures within the clays and limestone, particularly during wet periods of the year. Fluctuations of the groundwater level can occur due to seasonal variations in the amount of rainfall, runoff and other factors not evident at the time the borings were performed. The possibility of groundwater level fluctuations should be considered when developing the design and construction plans for the project. Groundwater conditions may require special attention if encountered during construction. ANALYSIS AND RECOMMENDATIONS The following recommendations have been developed on the basis of the previously described project characteristics and subsurface conditions. If there are any changes to the project characteristics or if different subsurface conditions are encountered during construction, ECS should be consulted so that the recommendations of this report can be reviewed. Site grading information was not provided during this report. Therefore, the following recommendations are based on the assumption that finished grade in the building area will be within 1½ feet of existing grade. If the finished floor elevation deviates from this assumed grade, the recommendations provided below should be re-evaluated by our office. Earthwork Operations In preparing the site for construction, all loose, poorly compacted existing soils, vegetation, organic soil, or other unsuitable materials should be removed from all proposed building and paving areas, and any areas receiving new fill. After stripping the site and prior to placing any fill, we recommend proofrolling the area with heavy construction equipment such as a fully loaded scraper or tandem axle dump truck with a minimum axle load of 10 tons. The purpose of the proofrolling is to attempt to locate any soft or compressible soils prior to placing new fill. Unsuitable materials located during proofrolling should be removed to firm ground and replaced with properly compacted fill as described in the following paragraphs. 4

10 ECS Project No. 19:5312 Prior to placement of any new fill, the subgrade should be scarified to a minimum depth of 6 inches, moisture conditioned and compacted to at least 95% of maximum standard Proctor dry density (ASTM D-698). Clay soils should be moisture conditioned to a workable moisture content above optimum value. Soil moisture levels should be preserved (by various methods that can include covering with plastic, watering, etc.) until new fill, pavements or slabs are placed. Placement and compaction of new fill will depend on soil type and its intended purpose. Fill used in the building pad area should be placed and compacted as described in the Building Pad Preparation section for reworked soils. Fill used in pavement areas should be placed in 9 inch loose lifts and compacted to at least 95% of maximum standard Proctor dry density (ASTM D-698) at a workable moisture content above optimum value. Fills placed in general landscape areas should be compacted to at least 90% of maximum standard Proctor dry density (ASTM D-698) at a workable moisture content near optimum value. Imported fills for general site grading should be similar to on-site soils, or preferably have a liquid limit less than 50. Upon completion of the filling operations, care should be taken to maintain the subgrade moisture content prior to construction of floor slabs and pavements. If the subgrade becomes desiccated, the affected material should be removed and replaced, or these materials should be scarified, moisture conditioned and recompacted. Utility cuts should not be left open for extended periods of time, and should be properly backfilled. Backfilling should be accomplished with properly compacted on-site soils, rather than granular materials. If granular materials are used, a utility trench cut-off at the building line is recommended to help prevent water from migrating through the utility trench backfill to beneath the proposed structure. Field density and moisture tests should be performed on each lift as necessary to verify that adequate compaction is achieved. As a guide, 1 test per 2,500 square feet per lift is recommended in the building areas. Utility trench backfill should be tested at a rate of 1 test per lift per each 300 linear feet of trench. Slope stability analysis of embankments (natural or constructed) was not within the scope of this study. If grading plans indicate slopes steeper than 4 (horizontal) to 1 (vertical) or greater than 3 feet high, it is recommended our office be contacted regarding stability analysis. Trench excavations should be braced or cut at stable slopes in accordance with Occupational Safety and Health Administration (OSHA) requirements and other applicable building codes. Building Pad Preparation The clay soils encountered at this site are considered active. These active soils can subject the lightly loaded interior floor slabs to movements (due to shrinking and swelling) with fluctuations in their moisture content. Based on test method TEX-124-E in the Texas Department of Transportation (TxDOT) Manual of Testing Procedures, results of the swell test, and our experience with similar soils, we estimate potential vertical soil movements (PVM) of about 4.25 inches could occur. The 5

11 ECS Project No. 19:5312 actual movements could be greater if poor drainage, ponded water, and/or other unusual sources of moisture are allowed to saturate the soils beneath the structure after construction. If interior floor slabs can tolerate movement, several methods can be considered to reduce movements to more tolerable levels and support the interior floor slabs on-grade. Methods that can be considered include installation of select fill alone and installation of select fill in conjunction with water injection. Installation of approximately 5 feet of select fill (without water injection) beneath the floor slabs can reduce PVM to about 1 inch or less. Greater depths of select fill could be required, if final subgrade elevations are more than 1½ feet above existing grade, and this office should be contacted for additional recommendations specific to final finished floor elevations. Installation of 1½ feet of select fill in combination with water injection of the on-site clays to a depth of 10 feet (or to the top of limestone, if encountered at shallower depths) could also reduce potential movements to less than 1 inch. Removal of a selected thickness of the clay fill soils and replacement with a non-expansive select fill material (resulting in a total of at least 5 feet of select fill below the floor slab) will reduce the PVM to 1 inch or less. Select fill material (such as clayey sand (SC) or sandy or silty clay (CL) that is free of debris and organic matter) should have a liquid limit less than 35, a plasticity index between 4 and 15, and contain no less than 25 percent passing the No. 200 sieve. The select fill should be placed in loose lifts of 9 inches or less and compacted to at least 95% of its standard Proctor dry density at a moisture content ranging from -2% to +3% of its optimum value. We have included in the appendix a set of General Specifications for the water injection process. Compliance with these specifications is essential to achieving maximum benefits from the injection(s). Multiple injections are typically required to obtain the desired moisture levels, and the time and expense for these injections will need to be included in the project schedule and budget. Very stiff to hard clays may be encountered during dry periods of the year. These clays can be difficult to penetrate, and may require heavy-duty injection equipment to achieve the recommended injection depth. In some cases the desired moisture levels and/or injection depths cannot be achieved, and this can result in an increase in potential movements. After completing the filling operations in the building pad area, care should be taken to maintain the subgrade moisture content prior to constructing the floor slab. If the subgrade becomes desiccated, the affected material should be scarified, moistened and recompacted prior to floor slab placement. Preventing large moisture fluctuations in the clay soils beneath the grade-supported floor slab is critical to slab performance. We recommend paving/sidewalks be placed adjacent to the structure perimeter to reduce seasonal drying of the moisture conditioned soils near the perimeter of the structure. Irrigation of lawn and landscaped areas should be moderate, with no excessive wetting or drying of soils around the perimeter of the structure allowed. Positive drainage away from the structure should also be provided. Trees and bushes/shrubs planted near the perimeter of the structure can withdraw large amounts of water from the soils and should be planted at least their anticipated mature height away from the building. 6

12 ECS Project No. 19:5312 If floor treatments that are sensitive to moisture will be used, a vapor barrier of polyethylene sheeting or similar material should be placed beneath the slabs to retard moisture migration through the slabs. If the above slab movements cannot be tolerated, the most positive method to reduce movements of interior slabs to very low levels would be to structurally suspend these slabs above the active clays. Foundation Recommendations The Strata I through III clayey soils encountered at this site can subject shallow foundation systems bearing on these soils to some differential movements due to moisture-induced volume changes in these soils. One method of supporting the proposed structure would be straight-sided drilled shafts bearing in the Stratum V gray limestone. Consideration can also be given to supporting the structure on a monolithic slab-on-grade foundation system provided it can withstand anticipated soil-related movements without impairing the structural or operational performance of the structure. Straight-Sided Drilled Shaft Foundation Straight-sided drilled shafts should bear at least 2 feet into the gray limestone encountered at depths of 17 feet below existing grade in the building area. The shafts will develop their load carrying capacity through a combination of end bearing and skin friction in the limestone strata. We recommend an allowable end bearing capacity of 45,000 psf in the gray limestone. Skin friction values of 4,500 psf may be used in the gray limestone. Skin friction should only be considered for that portion of the shaft extending into the gray limestone. Further, the minimum clear spacing between piers should be at least two pier shaft diameters to develop the full load carrying capacity from skin friction. Properly installed and constructed drilled shafts bearing in the gray limestone could be subject to potential settlements on the order of ½ inch or less. Expansion of the near surface clays with moisture increases can subject the shafts to uplift forces. The magnitude of these forces is difficult to estimate and depends on several factors including the insitu moisture levels at the time of construction and the availability of water. We estimate the magnitude of these forces to be approximately 1,200 psf for the soils extending to the top of tan weathered limestone. The uplift forces would be reduced to about 600 psf for moisture conditioned soils. 7

13 ECS Project No. 19:5312 Uplift forces must be resisted by the dead load on the shafts and uplift skin friction resistance in the limestone. We recommend using an allowable skin friction resistance of 3,600 psf in the gray limestone. The pier shafts should be a minimum of 18 inches diameter and contain sufficient reinforcing steel continuously throughout the shaft depth to resist anticipated tensile forces. Construction Considerations - Drilled Shafts Based on the groundwater conditions at the time of this subsurface investigation, the use of temporary steel casing does not appear necessary for drilled shaft construction. However, the contractor should plan for prompt placement of concrete into the excavation in order to limit possible seepage and sloughing. The possibility of encountering groundwater seepage during shaft installation increases during wet periods of the year. Concrete and steel should be placed as soon as possible after shaft excavations are complete to reduce the potential for seepage problems and deterioration of the bearing surface. During wet periods, seepage in the clays could, in some cases, require the use of temporary casing to properly install the shafts. The casing, if required, should be seated in the limestone below any seepage. All water should be removed from the cased excavation before beginning the design rock penetration. A sufficient head of concrete must be maintained in the casing during withdrawal. Installation of individual shafts should be completed in one day. The concrete placed for drilled shafts should have a slump between 5 and 7 inches and should be placed in a manner that prevents it from striking the reinforcing steel and sides of the excavation. We recommend that all drilled shafts be observed by qualified geotechnical personnel, to verify proper shaft installation. Grade Beams - Drilled Shafts All grade beams should be supported by the drilled shafts and formed with a nominal 8-inch void beneath the beam. This void is provided to isolate the grade beams from the underlying active clays. Cardboard carton forms can be used to create this void. A soil retainer should be provided to help prevent in fill of this void. Soils placed along the exterior of the grade beams should be on-site clay soils that are compacted to at least 95% of their maximum standard Proctor dry density. The clay fill should be compacted at a workable moisture content above its optimum value. The purpose of this clay backfill is to reduce the opportunity for surface water infiltration beneath the structure. 8

14 ECS Project No. 19:5312 Concrete Slabs-On-Grade Provided that a suitable subgrade is prepared as recommended herein, ground level slabs supported by engineered fill can be constructed as slabs-on-grade. Our findings indicate that a modulus of subgrade reaction (k s ) of 125 pci is appropriate for design provided the subgrade is prepared in accordance with the Building Pad Preparation/Floor Slabs section of this report. If floor treatments that are sensitive to moisture will be used, a vapor barrier (retarder) of polyethylene sheeting or similar material should be placed beneath the slab to retard moisture migration through the slab. If a vapor retarder is considered to provide moisture protection, special attention should be given to the surface curing of the slabs to minimize uneven drying of the slabs and associated cracking and/or slab curling. The use of a blotter or cushion layer above the vapor retarder can also be considered for project specific reasons. Please refer to ACI 302.1R96 Guide for Concrete Floor and Slab Construction and ASTM E 1643 Standard Practice for Installation of Water Vapor Retarders Used in Contact with Earth or Granular Fill Under Concrete Slabs for additional guidance on this issue. If a soil supported slab is used, we recommend that the floor slab be isolated from the foundation footings so differential settlement of the structure will not induce shear stresses on the floor slab. For maximum effectiveness, temperature and shrinkage reinforcements in slabs on ground should be positioned in the upper third of the slab thickness. The Wire Reinforcement Institute recommends the mesh reinforcement be placed 2 inches below the slab surface or upper one-third of slab thickness, whichever is closer to the surface. Adequate construction joints, contraction joints and isolation joints should also be provided in the slab to reduce the impacts of cracking and shrinkage. Please refer to ACI 302.1R96 Guide for Concrete Floor and Slab Construction for additional information regarding concrete slab joint design. If the potential slab movements discussed previously in this report cannot be tolerated, the most positive method to reduce movements of interior slabs to very low levels would be to structurally suspend these slabs above the active clays. A minimum void space of 8 inches should be provided between the floor system and any hanging fixtures (i.e. plumbing lines), and underlying subgrade. The ground surface beneath suspended floors should be shaped and drained to prevent the ponding of water. If a crawl space is provided below the floor slab, adequate ventilation should also be provided. Additionally, if a crawl space will be primarily below the level of existing grade, a vertical moisture barrier should be considered around the perimeter of the structure. If a suspended floor slab is used, the subgrade improvement discussed above would not be required. Monolithic Slab Foundation Consideration may be given to supporting the structure on a monolithic slab-on-grade foundation, provided that the Building Pad Preparation recommendations have been followed. An effective plasticity index of 58 is recommended for use in slab design and the following design parameters are recommended for the Post-Tensioning Institute's slab-on-grade design method: 9

15 ECS Project No. 19:5312 EDGE MOISTURE VARIATION Center Lift Edge Lift DIFFERENTIAL SWELL 5.2 feet 4.2 feet Potential Soil Movement, in. Differential Swell, inches (y m ) Edge Lift Center Lift (after subgrade improvement) These design parameters assume that positive drainage will be provided away from the structure and moderate irrigation of surrounding lawn and planter areas with no excessive wetting or drying of soils adjacent to the foundations. Greater potential movements could occur with extreme wetting or drying of the soils due to ponding of water, plumbing leaks or lack of irrigation. A net allowable soil bearing pressure of 2,500 psf can be used to design grade beams founded on the reworked existing soils or compacted select fill. Grade beams should have a minimum width of 12 inches to reduce the possibility of foundation bearing failure and excessive settlement due to local shear or "punching" failures. Additionally, the grade beams should extend at least 18 inches below final adjacent grade to utilize this bearing pressure. Fills should extend a minimum of 5 feet beyond the edge of the foundation and be sloped to drain surface water away from the structure. If floor treatments that are sensitive to moisture will be used, a properly designed and constructed vapor barrier of polyethylene sheeting or similar material should be placed beneath the slabs to retard moisture migration. The settlement of a structure is a function of the compressibility of the bearing materials, bearing pressure, actual structural loads, fill depths, and the bearing elevation of footings with respect to the final ground surface elevation. Estimates of settlement for foundations bearing on engineered or non-engineered fills are strongly dependent on the quality of fill placed. Factors that may affect the quality of fill include maximum loose lift thickness of the fills placed and the amount of compactive effort placed on each lift. If the recommendations outlined in this report are followed, we expect total settlements for the proposed construction to be in the range of 1 inch or less, while the differential settlement will be approximately one-half to three-quarters of the anticipated total settlement. This evaluation is based on our engineering experience and the anticipated loadings for this type of structure, and is intended to aid the structural engineer with his design. 10

16 ECS Project No. 19:5312 Exposure to the environment may weaken the soils at the foundation bearing level if the foundation excavations remain exposed during periods of inclement weather. Therefore, foundation concrete should be placed the same day that final excavation is achieved and the design bearing pressure verified. If the bearing soils are softened by surface water absorption or exposure to the environment, the softened soils must be removed from the foundation excavation bottom immediately prior to placement of concrete. If the foundation excavation must remain open overnight, or if rainfall is apparent while the bearing soils are exposed, we recommend that a 1 to 3-inch thick "mud mat" of "lean" concrete be placed over the exposed bearing soils before the placement of reinforcing steel. Pavement Subgrade All proposed paved areas should be proofrolled with heavy compaction equipment to attempt to locate any soft or undesirable soils so they can be removed and replaced with properly placed and compacted soils. The clay soils present at this site are highly plastic. The subgrade support value of these clays tends to decrease with increased moisture levels that normally occur beneath area paving. Treatment of the clay soils with hydrated lime will improve their subgrade characteristics to support area paving. Lime treatment of the clay soils is recommended for all clay subgrade areas supporting paving. We estimate a minimum of 8%-hydrated lime (by dry weight) should be used to modify the clay subgrade soils. The hydrated lime should meet the requirements of Item 264 (Type A) in the TxDOT Standard Specifications for Construction of Highways, Streets and Bridges, and should be thoroughly mixed and blended with the upper 6 inches of the clay subgrade (TxDOT Item 260). This mixture should be uniformly compacted to a minimum of 95% of its maximum Standard Proctor dry density (ASTM D-698) at a moisture content in the range of -2% to +3% as determined by that test. Lime treatment should extend at least 1 foot beyond exposed pavement edges to reduce the effects of shrinkage and associated loss of subgrade support. Density tests should be performed at a frequency of 1 test per 5,000 square feet of pavement. The actual amount of lime required should be confirmed by additional laboratory tests (lime series) during the construction phase. Pavement Sections Specific traffic loading information was not provided to ECS; however, light duty (automobile parking) pavements are expected to receive passenger vehicle. Our pavement section recommendations for heavy duty (drives) pavements should accommodate occasional heavier loadings due to delivery vehicle and light truck traffic and may be considered for main drives, service drives and loading dock areas. The recommended pavement sections are presented on the following page: 11

17 ECS Project No. 19:5312 Material Designation Asphaltic Concrete Pavement Portland Cement Concrete (PCC) Pavement Light Duty Heavy Duty Light Duty Heavy Duty Asphalt Surface Course 2 inches 2 inches Asphalt Binder Course 3 inches 4½ inches Portland Cement Concrete 5 inches 6 inches Lime Stabilized Subgrade 6 inches 6 inches 6 inches * 6 inches * *Note: In lieu of lime stabilization, the Portland cement concrete thickness should be increased by one inch. Front-loading trash dumpsters frequently impose concentrated front-wheel loads on pavements during loading. This type of loading typically results in rutting of bituminous pavements and ultimately pavement failures and costly repairs. Therefore, we suggest that the pavements in trash pickup areas utilize an 8 inch thick Portland Cement Concrete (PCC) pavement section. Appropriate steel reinforcing and jointing should also be incorporated into the design of all PCC pavement. An important consideration with the design and construction of pavements is surface and subsurface drainage. Where standing water develops, either on the pavement surface or within the base course layer, softening of the subgrade and other problems related to the deterioration of the pavement can be expected. Furthermore, good drainage should reduce the possibility of the subgrade materials becoming saturated during the normal service period of the pavement. Please note, the recommended pavement sections provided below are considered the minimum necessary to provide satisfactory performance based on the expected traffic loading. In some cases, City of McKinney minimum standards for pavement section construction may exceed those provided above. Pavement should be specified, constructed and tested to meet the following requirements: 1. Hot Mix Asphaltic Concrete: Item 340 of the TxDOT Standard Specifications, Type A or B Base Course (binder), Type D Surface Course. The coarse aggregate in the surface course should be crushed limestone rather than gravel. 2. Portland Cement Concrete: Item 360 of the TxDOT Standard Specifications. Specify a minimum compressive strength of 3,500 lbs per sq inch at 28 days. Concrete should be designed with 3 to 6 percent entrained air. 12

18 ECS Project No. 19:5312 It is recommended that the concrete pavements be reinforced with reinforcing bars (not welded wire fabric). As a minimum, the reinforcing bars should be #3 s spaced 18 inches on center in both directions (depending on the slab dimensions). The reinforcing should be placed on chairs approximately 1/3 the slab thickness below the surface, but not less than 2 inches. The reinforcing steel should not extend across expansion joints. Joints in concrete pavements aid in the construction and control the location and magnitude of cracks. Where practical, lay out the construction, expansion and control joints to form square panels, but not exceed ACI recommendations. The ratio of slab length-to-width should not exceed Recommended joint spacing are 15 feet in longitudinal direction and 15 feet in transverse direction. If possible, the pavement should develop a minimum slope of ft/ft to provide surface drainage. Reinforced concrete pavements should cure a minimum of 7 days before allowing any traffic. Seismic Site Class Determination The seismic Site Class may be determined by a calculating a weighted average strength of subsurface materials to a depth of 100 feet. Based upon the subsurface conditions encountered within the soil test borings that were advanced to depths of approximately 25 feet below the ground surface, we recommend that the Site Class for the site property be C as defined in Table of the International Building Code. Drainage Positive drainage should be provided around the entire building perimeter and pavement areas to prevent ponding of water. Pavement, sidewalks or flatwork are preferable to open areas around the building perimeter. Irrigation of lawn and landscaped areas adjacent to the structure should be moderate, with no excessive wetting or drying of soils adjacent to the structure. If landscaped areas are provided they should be sloped to drain away from the structure and landscape borders should allow water to drain freely away from the area. It is preferable that landscape beds immediately adjacent to the structure be self-contained, or a vertical moisture barrier provided between the landscaped area and the building. Closing We recommend that the construction activities be monitored by ECS to provide the necessary overview and to check the suitability of the subgrade soils for supporting the foundations and pavements. We would be most pleased to provide these services. 13

19 ECS Project No. 19:5312 This report has been prepared in order to aid in the evaluation of this property and to assist the architect and/or engineer in the design of this project. This report has been prepared in accordance with generally accepted geotechnical engineering practice. No other warranty is expressed or implied. The scope is limited to the specific project and locations described herein and our description of the project represents our understanding of the significant aspects relative to soil and foundation characteristics. In the event that any change in the nature or location of the proposed construction outlined in this report are planned, we should be informed so that the changes can be reviewed and the conclusions of this report modified or approved in writing by the geotechnical engineer. It is recommended that all construction operations dealing with earthwork and foundations be reviewed by an experienced geotechnical engineer to provide information on which to base a decision as to whether the design requirements are fulfilled in the actual construction. If you wish, we would welcome the opportunity to provide field construction services for you during construction. In a dry and undisturbed state, the upper 1 foot of the majority of the soil at the site will provide good subgrade support for fill placement and construction operations. However, when wet, this soil will degrade quickly with disturbance from contractor operations. Therefore, good site drainage should be maintained during earthwork operations which would help maintain the integrity of the soil. The surface of the site should be kept properly graded in order to enhance drainage of the surface water away from the proposed building areas during the construction phase. We recommend that an attempt be made to enhance the natural drainage without interrupting its pattern. The surficial soils contain fines which are considered moderately erodible. The Contractor should provide and maintain good site drainage during earthwork operations to help maintain the integrity of the surficial soils. All erosion and sedimentation shall be controlled in accordance with sound engineering practice and current jurisdictional requirements. The analysis and recommendations submitted in this report are based upon the data obtained from the soil borings and tests performed at the locations as indicated on the Boring Location Diagram and other information referenced in this report. This report does not reflect any variations, which may occur between the borings. In the performance of the subsurface exploration, specific information is obtained at specific locations at specific times. However, it is a well-known fact that variations in subsurface conditions exist on most sites between boring locations and also such situations as groundwater levels vary from time to time. The nature and extent of variations may not become evident until the course of construction. If variations then appear evident, after performing on-site observations during the construction period and noting characteristics and variations, a reevaluation of the recommendations for this report will be necessary. The assessment of site environmental conditions for the presence of pollutants in the soil, rock, and groundwater of the site was beyond the scope of this report. 14

20 APPENDIX Boring Location Diagram Boring Logs Reference Notes For Boring Logs Unified Soil Classification System Swell Test Results General Specification Water Pressure Injection

21 B-4 B-5 B-3 B-2 B-1 B-6 N GRAPHIC SCALE, FEET BORING LOCATION DIAGRAM Eldorado Pkwy. at Alma Road ECS Project No. 19:5312 October 15, 2007 Diagram Supplied by GHLA

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28 I. Drilling and Sampling Symbols: REFERENCE NOTES FOR BORING LOGS SS - Split Spoon Sampler ST - Shelby Tube Sampler RC - Rock Core: NX, BX, AX PM - Pressuremeter DC - Dutch Cone Penetrometer TC - Texas Cone Penetrometer RB - Rock Bit Drilling BS -Bulk Sample of Cuttings PA - Power Auger (no sample) HS - Hollow Stem Auger WS - Wash Sample Standard penetration (blows/ft) refers to the blows per foot of a 140 lb. hammer falling 30 inches on a 2 inch O.D. split spoon sampler, as specified in ASTM D The blow count is commonly referred to as the N-value. Texas cone penetrometer (blows/in) refers to the penetration of a 3-inch diameter cone after the cone is driven 100 blows with a 140 lb. hammer falling 30 inches. This is a modification of the Texas Department of Transportation test method TEX-132-E that requires a 170 lb. hammer falling 24 inches. II. Correlation of Penetration Resistances to Soil Properties: Relative Density-Sands, Silts Consistency of Cohesive Soils Unconfined Compressive SPT-N Relative Density Strength. Q P, psf Consistency 0-3 Very Loose under 500 Very Soft 4-9 Loose 500-1,000 Soft Medium Dense 1,000-2,000 Firm Dense 2,000-4,000 Stiff Very Dense 4,000-8,500 Very Stiff 8,500-16,000 Hard over 16,000 Very Hard III. Unified Soil Classification Symbols: GP - Poorly Graded Gravel GW -Well Graded Gravel GM -Silty Gravel GC - Clayey Gravels SP - Poorly Graded Sands SW -Well Graded Sands SM - Silty Sands SC - Clayey Sands ML - Low Plasticity Silts MH -High Plasticity Silts CL - Low Plasticity Clays CH - High Plasticity Clays OL - Low Plasticity Organics OH - High Plasticity Organics CL-ML - Dual Classification (Typical) IV. Water Level Measurement Symbols: WL - Water Level WS - While Sampling WD - While Drilling AB After Boring Completion BCR - Before Casing Removal ACR - After Casing Removal WCI - Wet Cave In DCl - Dry Cave In The water levels are those water levels actually measured in the borehole at the times indicated by the symbol. The measurements are relatively reliable when augering, without adding fluids, in a granular soil. In clays and plastic silts, the accurate determination of water levels may require several days for the water level to stabilize. In such cases, additional methods of measurement are generally applied.

29 Unified Soil Classification System (ASTM Designation D-2487) Major Division Group Symbol Typical Names Classification Criteria Coarse-grained soils More than 50% retained on No. 200 sieve Gravels More than 50% of coarse fraction retained on No. 4 sieve Sands More than 50% of coarse fraction passes No. 4 sieve GW GP GM GC SW SP SM SC Well-graded gravels and gravelsand mixtures, little or no fines Poorly graded gravels and gravelsand mixtures, little or no fines Silty gravels, gravel-sand-silt mixtures Clayey gravels, gravel-sand-clay mixtures Well-graded sands and gravelly sands, little or no fines Poorly graded sands and gravelly sands, little or no fines Silty sands, sand-silt mixtures Clayey sands, sand-clay mixtures Classification on basis of percentage of fines GW, GP, SW, SP GM, GC, SM, SC Borderline classification requiring use of dual symbol Less than 5% Pass No. 200 sieve More than 12% Pass No. 200 sieve 5% to 12% Pass No. 200 sieve C u = D 60 /D 10 Greater than 4 C z = (D 30 ) 2 /(D 10 xd 60 ) Between 1 and 3 Not meeting both criteria for GW Atterberg limits plot below A line or plasticity index less than 4 Atterberg limits plot above A line and plasticity index greater than 7 C u = D 60 /D 10 Greater than 6 C z = (D 30 ) 2 /(D 10 xd 60 ) Between 1 and 3 Not meeting both criteria for SW Atterberg limits plot below A line or plasticity index less than 4 Atterberg limits plot above A line and plasticity index greater than 7 Fine-grained soils 50% or more passing No. 200 sieve Silts and Clays Liquid limit 50% or less Silts and Clays Liquid limit greater than 50% ML CL OL MH CH Inorganic silts, very fine sands, rock flour, silty or clayey fine sands Inorganic clays of low to medium plasticity, gravelly clays, sandy clays, silty clays, lean clays Organic silts and organic silty clays of low plasticity Inorganic silts, micaceous or diatomaceous fine sands or silts, elastic silts Inorganic clays of high plasticity, fat clays PLASTICITY INDEX, PI Note: U-line represents approximate upper limit of LL and PI combinations for natural soils (empircally determined). ASTM-D2487. CL-ML CL or OL ML or OL U LINE CH or OH "A" LINE MH or OH LIQUID LIMIT, LL OH Organic clays of medium to high plasticity Plasticity chart for the classification of fine-grained soils. Tests made on fraction finer than No. 40 sieve Highly organic soils Pt Peat, muck and other highly organic soils Fibrous organic matter; will char, burn, or glow UNIFIED SOIL CLASSIFICATION SYSTEM

30 SWELL TEST RESULTS Eldorado Parkway at Alma Road ECS PROJECT NO. 19:5312 BORING SAMPLE DEPTH (ft) LIQUID LIMIT PLASTIC LIMIT PLASTICITY INDEX INITIAL MOISTURE (%) FINAL MOISTURE (%) B LOAD (psf) % SWELL

31 GENERAL SPECIFICATION WATER PRESSURE INJECTION 1. The injection process shall be observed on a full time basis by a qualified technician. This technician shall be under the direction of the owner s designated geotechnical engineer. 2. The injection process should be performed after the subgrade has been established to the desired elevation and prior to placement of select fill (if any), installation of underground utilities, and construction of pavements. 3. A nonionic surfactant (wetting agent) shall be added to the water for injection. The surfactant should be added in accordance with the manufacturer s recommendations. 4. Hole patterns on the lower portion of the injection rods shall be orientated to uniformly disperse the water throughout the injected zone. 5. Injection pressures shall be between 50 and 200 pounds per square inch and shall be adjusted to disperse as large a volume of water as possible. 6. The injection pipe shall be forced downward in 12 to 18 inch intervals to at least 10 feet. The pipes shall not be jetted or washed to achieve each penetration. 7. Injection shall continue to refusal at each injection interval (i.e. until the soil will not take any more fluid and fluid is running freely on the surface) to the specified injection depth. Refusal should be determined by an on site inspector. 8. Injection spacing shall not exceed 5 feet on center in each direction. Injections shall extend at least 5 feet beyond the building perimeter. Subsequent injection shall be offset from initial locations in a pattern that maximizes distribution of the injected water. 9. Evaluations of the moisture content in the injected zone shall be performed under the direction of the owner s designated geotechnical engineer. Continuous tube samples will be obtained in the injected zone following a minimum 48-hour curing period after the last injection pass. The engineer will develop recommendations on the need for additional injection passes based on the results of laboratory tests. 10. At completion of the injection process, the surface should be scarified to a depth of 6 inches and recompacted to a minimum of 93% of the maximum standard Proctor dry density as determined by ASTM D Completion of the building pad shall proceed in a timely manner after injection and recompaction is complete to preserve the moisture content of the injected soils. 12. Post injection evaluation of the building pad should include soil borings made in the completed building pad area at a minimum frequency of one boring per 10,000 square feet, or a minimum of two borings per building pad. The effectiveness of the water injection should be evaluated based on moisture contents, hand penetrometer values and swell potential. 13. The geotechnical engineer of record for the project should be retained to observe the entire injection process, provide post-injection laboratory testing, and evaluate the effectiveness of the injection process.