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MA1001-LR100407r April 7, 2010 Mr. George Marshall, P.E. City of Coppell 255 Parkway Blvd. Coppell, Texas 75019 Phone: (972) 304 -3562 Email: gmarshallCc�coppelltx.gov • GEOTECHNICAL ENGINEERING • ENVIRONMENTAL CONSULTING • CONSTRUCTION MATERIALS ENGINEERING AND TESTING Re: Geotechnical Investigation Pavement Reconstruction Intersection of Denton Tap Road & Sandy Lake Road Coppell, Texas AGG Report No. E10 -0308 Dear Mr. Marshall: Please find enclosed our report summarizing the results of the geotechnical investigation performed at the above referenced project. We trust the recommendations derived from this investigation will provide you with the information necessary to complete your proposed project successfully. For your future construction materials testing and related quality control requirements, it is recommended that the work be performed by Alliance Geotechnical Group, Inc. in order to maintain continuity of inspection and testing services for the project under the direction of the geotechnical project engineer. We thank you for the opportunity to provide you with our professional services. If we can be of further assistance, please do not hesitate to contact us. Sincerely, ALLIANCE GEOTECHNICAL GROUP, INC. -VA W ' Z � > �q 4N N� op Michael . Roland, P. MICHAEL DAINE HOLAN ...... D/ Mark J. Farrow, P. E. �.... � ........� Principal l 96 ........ .... 043 Senior Principal �� �' ��CENSti�•�� i ONAL�G F -1970 MEMBER 3228 Halifax Street • Suite A • Dallas, Texas 75247 ��� Tel: 972 - 444 -8889 • Fax: 972 - 444 -8893 • www.aggengr.com A01rt0.9 TABLE OF CONTENTS PAGE 1.0 INTRODUCTION ....................................................................... ............................... 1 1.1 PROJECT DESCRIPTION .............................................. ..............................1 1.2 PURPOSE AND SCOPE ................................................. ..............................1 2.0 FIELD INVESTIGATION ............................................................ ............................... 1 3.0 LABORATORY TESTING ........................................................... ..............................2 4.0 SITE AND SUBSURFACE CONDITIONS ................................... ..............................2 4.1 GENERAL SITE CONDITIONS ....................................... ..............................2 4.2 SUBSURFACE CONDITIONS ........................................ ..............................2 4.3 SITE GEOLOGY ............................................................. ..............................3 4.4 GROUNDWATER CONDITIONS .................................... ..............................3 5.0 ANALYSIS AND SUBGRADE RECOMMENDATIONS ............... ..............................3 5.1 SOIL MOVEMENTS ........................................................ ..............................3 5.2 PROOFROLLING AND FILL PLACEMENT .................... ..............................4 5.3 SITE GRADING AND DRAINAGE .................................. ..............................4 5.4 STABILIZATION WITH HYDRATED LIME ...................... ..............................5 5.5 RECOMPACTED PAVEMENT SUBGRADE ................... ..............................6 6.0 PAVEMENT RECOMMENDATIONS ......................................... ............................... 7 6.1 PAVEMENT SECTION RECOMMENDATIONS .............. ..............................7 6.2 PAVEMENT CONSIDERATIONS ................................... ..............................9 7.0 FIELD SUPERVISION AND CONSTRUCTION TESTING ......... ............................... 9 8.0 LIMITATIONS ............................................................................. ..............................9 FIGURES PLANOF BORINGS -------------------------------------------------------------------------------------- - - - - -1 LOGSOF BORINGS ------------------------------------------------------------------------------- - - - - -- 2 & 3 LEGEND - KEY TO LOG TERMS & SYMBOLS ---------------------------------------------------- - - - - -4 SWELLTEST RESULTS--------------------------------------------------------------------------------- - - - - -5 SOLUBLE SULFATE TEST RESULTS --------------------------------------------------------------- - - - - -6 LIME SERIES RESULTS--------------------------------------------------------------------------------- - - - - -7 ALLIANCE GEOTECHNICAL GROUP E10 -0308 GEOTECHNICAL INVESTIGATION PAVEMENT RECONSTRUCTION INTERSECTION OF DENTON TAP ROAD & SANDY LAKE ROAD COPPELL, TEXAS 1.0 INTRODUCTION 1.1 PROJECT DESCRIPTION The project consists of replacing the existing intersection of Denton Tap Road & Sandy Lake Road in Coppell, Texas. We understand that this existing pavement section consists of pavers over 8 inches of concrete. We further understand that the existing pavers / concrete will be removed and replaced with full depth concrete pavement. We understand that this street will be reconstructed to the same edge to edge dimensions and at the same pavement grades and that widening will not be performed. 1.2 PURPOSE AND SCOPE The purposes of this geotechnical investigation were to: 1) explore the subsurface conditions at the site, 2) provide boring logs that present subsurface conditions encountered including water level observations and laboratory test results, 3) provide pavement subgrade stabilization recommendations, and 5) provide concrete pavement recommendations. This report was prepared in general accordance with our proposal number P10 -0309E dated March 22, 2010. 2.0 FIELD INVESTIGATION The field investigation consisted of drilling two (2) pavement borings to depths of 10 feet. The test borings were drilled through the existing pavement. A truck - mounted drilling rig was used to advance these borings and to obtain samples for laboratory evaluation. The borings were located at the approximate locations shown on the Plans of Borings (Figure 1). Undisturbed samples of the soils were obtained at intermittent intervals with standard, thin - walled, seamless tube samplers. These samples were extruded in the field, logged, sealed, and packaged to protect them from disturbance and maintain their in -situ moisture content during transportation to our laboratory. ALLIANCE GEOTECHNICAL GROUP E10 -0308 PAGE 1 The results of the boring program are presented on the Logs of Borings, Figures 2 and 3. A key to the descriptive terms and symbols used on the logs is presented on Figure 4. 3.0 LABORATORY TESTING Laboratory tests were performed on representative samples of the soil to aid in classification of the soil materials. These tests included Atterberg limits tests, percent passing #200 sieve, moisture content tests and dry unit weight determinations. Hand penetrometer tests were performed on the soil samples to provide indications of the swell potential and the foundation bearing properties of the subsurface strata. The results of these tests are presented on the Logs of Borings (Figures 2 and 3). To provide additional information about the swell characteristics of these soils (at their in -situ moisture conditions), absorption swell tests were performed on selected samples of the clay soils (see Figure 5). Soluble sulfate testing was also performed on selected samples (see Figure 6). A lime / Atterberg limits series test was performed on a selected clay soil sample (see Figure 7.) 4.0 SITE AND SUBSURFACE CONDITIONS 4.1 GENERAL SITE CONDITIONS The project consists of reconstructing the intersection of Denton Tap Road and Sandy Lake Road in Coppell, Texas. See Plan of Borings (Figure 1) for site configuration, location and aerial view. 4.2 SUBSURFACE CONDITIONS Subsurface conditions encountered in the borings, including descriptions of the various strata and their depths and thickness, are presented on the Logs of Borings. Note that depth on all borings refers to the depth from the existing grade or ground surface present at the time of the investigation. Boundaries between the various soil types are approximate. ALLIANCE GEOTECHNICAL GROUP E10 -0308 PAGE 2 4.3 SITE GEOLOGY As shown on the Dallas sheet of the Geologic Atlas of Texas the project site is located in an area underlain by deposits of the Woodbine Formation. This Formation typically consists of shale, sandstone, and cemented sand interbedded with clay seams. Soils derived from the formation are typically moderately to highly active clays exhibiting moderate to high shrink /swell potential with variations in moisture content. 4.4 GROUNDWATER CONDITIONS The borings were advanced using continuous flight auger methods. Advancement of the borings using these methods allows observation of the initial zones of seepage. No groundwater was encountered in the test borings during drilling. We were unable to obtain delayed water level readings since the borings had to be backfilled and pavement patched immediately after drilling completion. It is not possible to accurately predict the magnitude of subsurface water fluctuations that might occur based upon short -term observations. The subsurface water conditions are subject to change with variations in climatic conditions and are functions of subsurface soil conditions, rainfall and water levels within nearby creeks and ponds. 5.0 ANALYSIS AND SUBGRADE RECOMMENDATIONS 5.1 SOIL MOVEMENTS The subsurface exploration revealed the presence of active clay and sandy clay soils. The surficial clay soils have a moderate to high shrink /swell potential depending upon their moisture condition at the time of construction. Potential Vertical Rise (PVR) calculations were performed using moisture contents, penetrometer readings, and swell test results to estimate the swell potential of the soil. PVR values based on current grades and current moisture conditions have been estimated to range from 2 to 3 inches. It should be noted that if the clay soils are allowed to significantly dry after pavement removal and prior to placing the new pavement that the potential vertical rise could increase to over 4+ inches. ALLIANCE GEOTECHNICAL GROUP E10 -0308 PAGE 3 It is imperative that all cracks and joints in the pavement be sealed and maintained by routine sealing in order to minimize differential pavement deflections caused by soil swelling. It is also imperative that positive drainage be provided along the pavement edges to prevent ponding near the curb lines. 5.2 PROOFROLLING AND FILL PLACEMENT Prior to placing fill, the exposed subgrade at base of cut should be proofrolled. Proofrolling should also be performed after removing the existing pavement and cutting to final grades. Proofrolling can generally be accomplished using a heavy (25 ton or greater total weight) pneumatic tired roller making several passes over the areas. The proofrolling operations should be performed under the direction of the geotechnical engineer. Where soft or compressible zones are encountered, these areas should be removed to a firm subgrade. Any resulting void areas should be backfilled to finished subgrade in 8 inch compacted lifts as specified below. After completion of proofrolling, the ground surface should then be scarified to a depth of 8 inches and recompacted to levels specified below prior to placement of additional fill. We recommend that fill soils be compacted at -11% to +3% above optimum to 98% of standard Proctor density (ASTM D698). 5.3 SITE GRADING AND DRAINAGE All grading should provide positive drainage away from the proposed roadway and should prevent water from collecting or discharging near the pavements. Water must not be permitted to pond adjacent to or beneath the pavements during or after construction. Otherwise, upward soil swell movements could exceed the estimates contained in this report. The pavements will be subject to some post construction movement (see Section 5.1 of this report). Joints in the concrete pavements should be sealed to prevent the infiltration of water. Since post construction movement of pavement may occur, joints should be periodically inspected and resealed where necessary. ALLIANCE GEOTECHNICAL GROUP E10 -0308 PAGE 4 5.4 STABILIZATION WITH HYDRATED LIME The subsurface exploration revealed surficial materials consisting of plastic clay and sandy clay soils having a moderate to high shrink /swell potential. These clay soils react with hydrated lime, which serves to improve their support value and provide a firm, uniform subgrade beneath the paving. Based on the anticipated soil materials to be exposed at pavement subgrade and based upon a Lime / Atterberg Limits series test (see Figure 7) performed on a selected clay sample, seven (7) percent hydrated lime by dry weight (48 pounds per square yard per 8- inch depth) will be required to stabilize the existing clay subgrade. Soluble sulfate testing on selected samples of the clay soils resulted in soluble sulfate concentrations ranging from 100 to 130 (see Figure 6). Based upon these concentration levels, the risk of sulfate / lime induced heave is low. The lime should be thoroughly mixed and blended with the active subgrade soil (TxDOT Item 260) and the mixture compacted to a minimum of 95 percent of maximum dry density as determined in accordance with ASTM D698, within -1% to +3% of the soil's optimum moisture content. We recommend that this lime stabilization extend 1 to 2 feet beyond exposed pavement edges, if possible, in order to reduce the effects of shrinkage during extended dry periods. After final grading has been achieved, depth checks should be performed to verify that the specified depth of stabilization is present. Sand should be specifically prohibited beneath pavement areas during final grading (after stabilization), since these more porous soils can allow water inflow, resulting in heave and strength loss of subgrade soils. It should be specified that only lime- stabilized soil will be allowed for fine grading. After fine grading each area in preparation for paving, the subgrade surface should be lightly moistened, as needed, and recompacted to obtain a tight non - yielding subgrade. Project specifications should allow a curing period between initial and final mixing of the lime /soil mixture. After initial mixing, the lime treated subgrade should be lightly rolled and maintained at or within 5 percentage points above the soil's optimum moisture content until final mixing and compaction. We recommend a 3 -day curing period for these soils. The ALLIANCE GEOTECHNICAL GROUP E10 -0308 PAGE 5 following gradation requirements are recommended for the stabilized materials prior to final compaction: Minimum Passing 1 3/4" Sieve Minimum Passing 3/4" Sieve Minimum Passing No. 4 Sieve Percent 100 85 60 All non - slaking aggregates retained on the No. 4 sieve should be removed prior to testing. After final grading has been performed, depth checks and PI verification checks should be performed to verify that proper stabilization has been achieved. The prepared subgrade should be protected and moist cured or sealed with a bituminous material for a minimum of 7 days or until the pavement materials are placed. Pavement areas should be graded at all times to prevent ponding and infiltration of excessive moisture on or adjacent to the pavement areas. Due to the presence of expansive clay soils, pavement movements should be anticipated. Inspection during construction is particularly important to insure proper construction procedures are followed. 5.5 RECOMPACTED PAVEMENT SUBGRADE If lime- stabilization of the pavement subgrade is not performed, we recommend that the upper eight -(8) inches of subgrade soil be compacted at -2% to +2% of optimum moisture to a minimum of 98% Standard Proctor density (ASTM D 698). The subgrade should be proof- rolled prior to subgrade compaction. Only on -site soil (comparable to the underlying subgrade soil) should be used for fine grading the pavement areas. After fine grading, the subgrade should again be watered if needed and re- compacted in order to re- achieve the moisture and density levels discussed above and provide a tight non - yielding subgrade. Sand should be specifically prohibited beneath pavement areas during final grading, since these more porous soils can allow water inflow, resulting in heave and strength loss of subgrade soils. It should be specified that only clay soils will be allowed for fine grading. After fine grading each area in preparation for paving, the subgrade surface should be lightly moistened, as needed, and recompacted to obtain a tight non - yielding subgrade. ALLIANCE GEOTECHNICAL GROUP E10 -0308 PAGE 6 The subgrade moisture content and density must be maintained until paving is completed. The subgrade should be watered just prior to paving to assure concrete placement over a moist subgrade. If a rain event occurs prior to paving, the subgrade should be aerated and re- tested prior to paving. Due to the presence of expansive clay soils, post construction upward pavement movements should be anticipated. Inspection during construction is particularly important to insure proper construction procedures are followed. 6.0 PAVEMENT RECOMMENDATIONS The required pavement section depends on the traffic volume and the frequency of truck traffic. We understand that the following design traffic data should be used for the design lane. Annual ESALs 300,000 Growth Rate 2.5% Design Life 30 Years The pavement section recommendations provided below in this report have been developed based upon the above traffic information: 6.1 PAVEMENT SECTION RECOMMENDATIONS The pavement section recommendations provided below were designed based upon AASHTO Guide for Design of Pavement Structures using DARWin 3.1 computer program. A summary of the inputs are provided below: Design E 18's: 13,171,000 Initial Serviceability: 4.5 Terminal Serviceability: 2.5 Modulus of Rupture: 588 psi (4,000 psi Concrete) Elasticity Modulus: 3,969,000 psi Effective k- value: 225 psi /in - for 8 inches of lime- stabilized subgrade 100 psi /in — for 8 inches of compacted subgrade Reliability Level: 85% Standard Deviation: 0.39 Load Transfer J: 3.2 Drainage Coefficient: 1.0 ALLIANCE GEOTECHNICAL GROUP E10 -0308 PAGE 7 Table 1 presents the recommended pavement section for this project: TABLE 1 - RECOMMENDED PAVEMENT SECTIONS PAVEMENT RECONSTRUCTION 11.0 inch Portland Cement Concrete* 8.0 inch Lime - Stabilized Subgrade ** Or 12.0 inch Portland Cement Concrete * ** 8.0 inch Compacted Subgrade * * ** * A construction tolerance of about '/a inch is included. ** Should be placed in accordance with Section 5.4 of this report. * ** A construction tolerance of about 1 /2 inch is included. * * ** Should be placed in accordance with Section 5.5 of this report. The concrete should have a minimum 28 day compressive strength of 4,000 psi and a minimum 28 day flexural strength of 588 psi. Concrete quality will be important in order to produce the desired flexural strength and long term durability. Assuming a nominal maximum aggregate size of 1 inch to 1 3/8 inches, we recommend that the concrete have entrained air of 5 percent (± 1 %) with a maximum water cement ratio of 0.45. Proper joint placement and design is critical to pavement performance. Load transfer at all joints and maintenance of watertight joints should be provided. Control joints should be sawed as soon as possible after placing concrete and before shrinkage cracks occur. All joints including sawed joints should be properly cleaned and sealed as soon as possible to avoid infiltration of water. Our previous experience indicates that joint spacing on 12 to 15 foot centers have generally performed satisfactorily. It is our recommendation that the concrete pavement be reinforced with a minimum of No. 3 bars placed on chairs on approximately 18 —inch centers in each ALLIANCE GEOTECHNICAL GROUP E10 -0308 PAGE 8 direction. We recommend that the perimeter of the pavements have a stiffening section to prevent possible distress due to heavy wheel loads near the edge of the pavements. 6.2 PAVEMENT CONSIDERATIONS All joints and pavements should be inspected at regular intervals to ensure proper performance and to prevent crack propagation. The soils at the site are active and differential heave within the paving areas could potentially occur. The service life of paving may be reduced due to water infiltration into subgrade soils through heave induced cracks in the paving section. This will result in softening and loss of strength of the subgrade soils. A regular maintenance program to seal paving cracks will help prolong the service life of the paving. The life of the pavement can be increased with proper drainage. Areas should be graded to prevent ponding adjacent to curbs or pavement edges. Backfill materials, which could hold water behind the curb, should not be permitted. Flat pavement grades should be avoided. 7.0 FIELD SUPERVISION AND CONSTRUCTION TESTING Field density and moisture content determinations should be made on each lift of fill with a minimum of 1 test per lift per 5,000 square feet of pavement. Supervision by the field technician and the project engineer is required. Some adjustments in the test frequencies may be required based upon the general fill types and soil conditions at the time of fill placement. Many problems can be avoided or solved in the field if proper inspection and testing services are provided. It is recommended that site preparation, lime- stabilization, concrete placement, and fill compaction be monitored by a qualified engineering technician. Density tests should be performed to verify compaction and moisture content of any earthwork. Inspection should be performed prior to and during concrete placement operations. Alliance Geotechnical Group, Inc. employs a group of experienced, well- trained technicians for inspection and construction materials testing who would be pleased to assist you on this project. 8.0 LIMITATIONS The professional services, which have been performed, the findings obtained, and the recommendations prepared were accomplished in accordance with currently accepted ALLIANCE GEOTECHNICAL GROUP E10 -0308 PAGE 9 geotechnical engineering principles and practices. The possibility always exists that the subsurface conditions at the site may vary somewhat from those encountered in the test borings. The number and spacing of test borings were chosen in such a manner as to decrease the possibility of undiscovered abnormalities, while considering the nature of loading, size, and cost of the project. If there are any unusual conditions differing significantly from those described herein, Alliance Geotechnical Group, Inc. should be notified to review the effects on the performance of the recommended foundation system. The recommendations given in this report were prepared exclusively for the use of the City of Coppell and their consultants. The information supplied herein is applicable only for the design of the previously described development to be constructed at locations indicated at this site and should not be used for any other structures, locations, or for any other purpose. We will retain the samples acquired for this project for a period of 30 days subsequent to the submittal date printed on the report. After this period, the samples will be discarded unless otherwise notified by the owner in writing. ALLIANCE GEOTECHNICAL GROUP E10 -0308 PAGE 10 FIGURES P f I� I I awo O 1 N 11'C 1 ntt p:!Aqww . d ,qpa w ... Pavement Reconstruction PLAN OF BORINGS FIGURE ALLIANCE Denton Tap & Sandy Lake, Coppell GEOTECHNICAL GROUP Drawn b fv�DR Date 4/06/10 Revised N/A Scale 1 " 50' Protect No E10 -0308 LOG OF BORING B -1 Project: Pavement Reconstruction - Denton Tap & Sandy Lake - Coppell, Texas Project No.: E10 -0308 Date: 03/26/2010 Elev.: Location: See Figure 1 Depth to water at completion of boring: Dry Depth to water when checked: during drilling was: Dry Depth to caving when checked: was: ELEVATION/ SOIL SYMBOLS DEPTH SAMPLER SYMBOLS DESCRIPTION MC LL PL 200 DD P.PEN UNCON Strain feet & FIELD TEST DATA % % % P % pd tsf ksf % ( Via: — — -— -2.5 - 5 -7.5 10 12.5 15 17.5 3 PAVER over 1 SAND over 8 CONCRETE Reddish brown & tan CLAY w/ sand (FILL) 77 19 Reddish brown sandy CLAY w/ trace gravel 3.6 — — 4.4 16 48 16 32 116 4.5+ Light brown & light gray sandy CLAY w/ gravel 45 + 13 36 13 23 124 4.5+ 4.5+ Light brown &light gray sandy CLAY numerous 4.5+ gravel 4.3 Light brown & light gray sandy CLAY w/ sand seams 3.6 — — 4.3 Boring terminated at 10' Notes: FIGURE:2 ALLIANCE GEOTECHNICAL GROUP LOG OF BORING B -2 Project: Pavement Reconstruction - Denton Tap & Sandy Lake - Coppell, Texas Project No.: E10 -0308 Date: 03/26/2010 Elev.: Location: See Figure 1 Depth to water at completion of boring: Dry Depth to water when checked: during drilling was: Dry Depth to caving when checked: was: ELEVATION/ SOIL SYMBOLS MC LL PL -200 DD P.PEN UNCON Strain DEPTH SAMPLER SYMBOLS DESCRIPTION PI (feet) & FIELD TEST DATA % % % % PCf tsf ksf F0 3" PAVER over I SAND over 6.5" CONCRETE Brown & gray sandy CLAY w/ gravel (FILL) 3 -0 Reddish brown & gray very sandy CLAY ,s 30 13 17 5s 3.25 — — 16 2.25 -2.5 -5 -7.5 2.0 Reddish brown & light gray very sandy CLAY 15 57 1 — s 1.75 Light brown & light gray CLAY w/ sand f4.3 3.6 4.2 4.4 10 12.5 15 17.5 Notes Boring terminated at 10' 1 1 1 1 1 1 1 1 1 FIGURE:3 ALLIANCE GEOTECHNICAL GROUP KEY TO LOG TERMS & SYMBOLS Symbol Description Strata symbols :tz.o;e Paver over Sand over Concrete .d• Oy15 . z CLAY CLAY, sandy Soil Samplers Rock Core Thin Wall Shelby Tube I1. Exploratory borings were drilled on dates indicated using truck mounted drilling equipment. 12. Water level observations are noted on boring logs. 3. Results of tests conducted on samples recovered are reported on the boring logs. Abbreviations used are: DD = natural dry density (pcf) LL = liquid limit (%) MC = natural moisture content M PL = plastic limit (%) Uncon.= unconfined compression (tsf) PI = plasticity index P.Pen.= hand penetrometer (tsf) -200 = percent passing #200 4. Rock Cores REC = (Recovery) sum of core sample recovered divided by length of run, expressed as percentage. RQD = (Rock Quality Designation) sum of core sample recovery 4" or greater in length divided by the run, expressed as percentage. FIGUREA1 ALLIANCF GFOTFCHNICAI GROl1P SWELL TEST RESULTS BORING DEPTH UNIT ATTERBERG LIMITS IN -SITU FINAL LOAD % NO. (FEET) WEIGHT MOISTURE MOISTURE (PSF) VERTICAL LL PL pi CONTENT CONTENT SWELL B -1 2 -3 116.2 48 16 32 15.9 17.8 313 2.7 B -1 4 -5 123.8 36 13 23 12.7 13.6 563 0.8 PROCEDURE: 1. Sample placed in confining ring, design load (including overburden) applied, free water with surfactant made available, and sample allowed to swell completely. 2. Load removed and final moisture content determined. SOLUBLE SULFATES TEST RESULTS (PPM) BORING NO. DEPTH (FEET) SOLUBLE SULFATES (PPM) B -1 1 - 1.5 130 B -1 2-3 100 B -1 4-5 110 ALLIANCE G GEOTECNnICHL GROUP LIME SERIES RESULTS BORING DEPTH LIME LIQUID PLASTICITY NO. (FEET) ADDED LIMIT INDEX (PI) ( /o) ( /o) 0 48 32 4 15 17 B -1 2 -3 6 42 11 8 40 9 ALLIANCE qG GEOTECHnICAL GROUP