GEOTECHNICAL INVESTIGATION MDACC GUHN ROAD FLOOD MITIGATION PROJECT 5610 GUHN ROAD HOUSTON, TEXAS REPORT NO

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1 GEOTECHNICAL INVESTIGATION MDACC GUHN ROAD FLOOD MITIGATION PROJECT 5610 GUHN ROAD HOUSTON, TEXAS REPORT NO Reported to: URS CORPORATION Houston, Texas Reported by: GEOTEST ENGINEERING, INC. Houston, Texas Harris County Key Map No. 450 C

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3 TABLE OF CONTENTS Page 1.0 EXECUTIVE SUMMARY INTRODUCTION General Project Description Purpose and Scope of Work FIELD EXPLORATION General Drilling and Sampling Methods Piezometer Installation Groundwater Observations Borehole Completion LABORATORY TESTING SITE GEOLOGY Geologic Formation Geologic Faults in the Vicinity of Site GENERAL SITE CONDITIONS Existing Surface Conditions Soil Stratigraphy Groundwater Conditions GEOTECHNICAL ENGINEERING RECOMMENDATIONS Flood Wall Foundation Lateral Pressure Evaluation CONSTRUCTION CONSIDERATIONS Foundation Excavations Structural Fill Requirements Groundwater Control Construction Monitoring PROVISIONS... 17

4 TABLE OF CONTENTS (cont d) ILLUSTRATIONS Figure Vicinity Map... 1 Plan of Borings... 2 Boring Log Profile and 3.2 Symbols and Abbreviations Used on Boring Log Profile... 4 Design Equations for Drilled Piers Subject to Overturning Moments... 5 TABLE Table Summary of Boring Information... 1 APPENDIX A Figure Logs of Borings... A-1 thru A-4 Symbols and Terms Used on Boring Logs... A-5 Piezometer Installation Report... A-6 and A-7 APPENDIX B Figure Summary of Laboratory Test Results... B-1 thru B-4 Permeability Laboratory Test Data... B-5 and B-6 APPENDIX C Page Results of Aggressive Tests... 1 thru 12

5 Geotest Engineering, Inc. Report No UTMDACC Guhn Road Flood Mitigation Project November 21, Guhn Road; Houston, Texas 1.0 EXECUTIVE SUMMARY A geotechnical Investigation was conducted in connection with the design of a new castin-place concrete freestanding cantilever flood wall to be built at the MDACC Data Center located at 5610 Guhn Road, Houston, Texas. The wall will be designed to withstand static water pressure up to an elevation of 89 feet. Current existing grade is approximately at Elevation 85 feet. In addition, new elevated platforms might be constructed for ramps and equipment outside the building. This geotechnical investigation included drilling and sampling four (4) soil borings each to a depth of 25 feet. The scope of work also included performing laboratory tests on soil samples recovered from the borings and engineering analyses. The principal findings and conclusions developed from this investigation are summarized below: Based on the published documents, no faults appear to be within a 1-mile radius of the project site. The closest documented fault, White Oak Fault (part of Addicks Fault System), is about 1.7 miles north of the project site and the Long Point Fault is approximately 3 miles south of the project site. The existing paving, as revealed by borings GB-1 and GB-4 drilled in the pavement area, consists of 4.75 inches of concrete over 1.5 to 2 inches of brown silty sand. The top (fill) soils, as revealed by borings GB-2 and GB-3 drilled in the grass and planter areas, consist of dark gray and gray sandy silt and sandy clay with roots and calcareous nodules to a depth of about 2 feet below the existing ground surface. The subsurface soils beneath the top soils or existing paving consists of medium stiff to very stiff gray, brown and yellowish brown Sandy Clay (CL) to depths varied from 6 to 25 feet. The sandy clay is underlain by stiff to very stiff gray and yellowish brown or gray and reddish brown Clay (CH) to a depth of 25 feet, the maximum depth explored, in borings GB-1, GB-3 and GB-4. The clay is slickensided. In boring 1

6 Geotest Engineering, Inc. Report No UTMDACC Guhn Road Flood Mitigation Project November 21, Guhn Road; Houston, Texas GB-4, stiff dark gray Clay (CH) was encountered beneath the paving to a depth of about 4 feet. Groundwater was initially encountered at depths ranging from about 11 to 18 feet below existing grade in borings GB-1 and GB-2 during the drilling operation. No groundwater was encountered during drilling operation in other borings, GB-3 and GB-4. Depth to ground water, as observed in Piezometers GB-1P and GB-3P, ranges from about 6 to 8 feet. Geotechnical recommendations for the flood wall structure foundation are provided in Section 7.0 of this report. Construction considerations including foundation excavation, structural fill requirements and groundwater control, etc. are provided in Section 8.0 of this report. 2

7 Geotest Engineering, Inc. Report No UTMDACC Guhn Road Flood Mitigation Project November 21, Guhn Road; Houston, Texas 2.0 INTRODUCTION 2.1 General Geotest Engineering, Inc. (Geotest) is pleased to present the report of our geotechnical investigation for the MDACC Guhn Road Flood Mitigation Project. 2.2 Project Description The project is located in MDACC Data Center at 5610 Guhn Road in Houston, Texas. A project vicinity map is shown on Figure 1. A new east-in-place concrete freestanding cantilever flood wall is proposed to surround the existing building. The existing building is a single story steel framed structure with concrete tilt-up exterior wall panels. The ground floor level is slabon-grade and the foundation system may consist of pier and beam. The depth of piers is unknown. The wall will be designed to withstand static water pressure up to an elevation of feet. Current existing grade is approximately at Elevation 85 feet. In addition, new elevated platforms might be constructed for ramps and equipment outside the building. 2.3 Purpose and Scope of Work The purposes of this geotechnical study were to explore and evaluate subsurface soil and groundwater conditions at the project site and to develop geotechnical engineering recommendations for the design of the proposed flood wall structure. The scope of work for this study included the following: drill and sample four (4) 25-foot borings below existing grade to explore subsurface soil and groundwater conditions and to obtain soil samples for laboratory testing; install piezometers in two (2) existing borings to monitor static ground water level. 3

8 Geotest Engineering, Inc. Report No UTMDACC Guhn Road Flood Mitigation Project November 21, Guhn Road; Houston, Texas perform field and laboratory tests on select soil samples to assess pertinent geotechnical engineering properties; analyze the field and laboratory data to develop geotechnical engineering recommendations pertaining to the design of the flood wall structure foundations; provide ground-fault information; prepare a geotechnical engineering report documenting the results of field investigation, laboratory testing and geotechnical engineering recommendations. 4

9 Geotest Engineering, Inc. Report No UTMDACC Guhn Road Flood Mitigation Project November 21, Guhn Road; Houston, Texas 3.0 FIELD EXPLORATION 3.1 General Our field exploration program was conducted on September 11, Subsurface soil and groundwater conditions were explored by drilling four (4) soil borings each to a depth of 25 feet below the existing grade. The boring locations were primarily selected by Walter P. Moore (WPM), and located in the field by Geotest representatives. Some of the original locations were shifted to accommodate existing limitations, such as underground utility lines. The approximate boring locations, designated as GB-1 through GB-4, are shown on the Plan of Borings, Figure 2. A summary of boring information is provided in Table 1. Detailed descriptions of the soils encountered in the borings drilled for this project are presented on the boring logs on Figures A-1 through A-4 in Appendix A. A key identifying the terms and symbols used on the boring logs are presented on Figure A-5 in Appendix A. 3.2 Drilling and Sampling Methods The soil borings for this study were drilled with a truck-mounted drilling rig using both dry-auger and wet-rotary techniques. Samples were obtained continuously to a 20-foot depth and at 5-foot intervals there on. Undisturbed samples of cohesive soils were obtained by hydraulically pushing a 3-inch diameter, thin-walled tube sampler in general accordance with the Standard Practice for Thin-Walled Tube Sampling of Soils (ASTM D 1587). Granular samples were obtained using the Standard Penetration Test (SPT) with a 2-inch split-spoon barrel in general accordance with the ASTM Method D Each soil sample was removed from the sampler in the field, carefully examined, and then logged by an experienced soil technician. Portions of each sample were sealed and packaged for transportation to Geotest s laboratory for further testing. The field estimates of the undrained shear strength of the recovered cohesive soil samples were obtained using a calibrated hand penetrometer. 5

10 Geotest Engineering, Inc. Report No UTMDACC Guhn Road Flood Mitigation Project November 21, Guhn Road; Houston, Texas boring logs. Driving resistances for the split-barrel samples were recorded as Blows per Foot on the 3.3 Piezometer Installation During the field investigation, piezometers were installed in the open boreholes of borings GB-1 and GB-3. The location of piezometers, designated as GB-1P and GB-3P, are shown on Plan of Borings on Figure 2. The piezometer installation record showing the details of the construction of piezometers are provided on Figures A-6 and A-7 in Appendix A. 3.4 Groundwater Observations Measurements of the depth to water were taken into the open boreholes during drilling and also in the piezometers. The results of these observations are noted at the bottom of the boring logs and piezometer installation reports in Appendix A. 3.5 Borehole Completion Upon completion of the field investigation, each of the boreholes with the exception of borings converted to piezometers, were grouted with cement-bentonite grout. Each borehole was grouted from the bottom up using a tremie pipe. When grout returned to the surface, we removed the tremie pipe and topped off each borehole by pouring grout from the surface. 6

11 Geotest Engineering, Inc. Report No UTMDACC Guhn Road Flood Mitigation Project November 21, Guhn Road; Houston, Texas 4.0 LABORATORY TESTING A laboratory test program was developed to measure pertinent physical and strength characteristics of representative samples from the field exploration. Classification tests were performed on selected samples to aid in soil classification. All geotechnical tests were performed in accordance with ASTM procedures. Undrained shear strengths of selected cohesive soil samples were measured by unconfined compression (ASTM D 2166) and unconsolidated-undrained (U-U) triaxial compression (ASTM D 2850) tests. Shear strengths of cohesive samples were also estimated in the field using a calibrated hand pocket penetrometer and in the laboratory with a Torvane. Moisture content (ASTM D 2216) and dry unit weight were measured for each unconfined compression and U-U triaxial compression test sample. Moisture content measurements were also conducted on most samples to identify the moisture profile at each boring location. Liquid and plastic limit tests (ASTM D 4318) were performed on selected cohesive and semi-cohesive samples to measure soil plasticity characteristics and to aid in soil classification. Percent finer than No. 200 sieve tests (ASTM D 1140) were performed on selected samples to aid in soil classification. Results of most laboratory tests are tabulated on the boring logs presented on Figures A-1 through A-4 in Appendix A. All the laboratory tests data are summarized in the Summary of Laboratory Test Results presented on Figures B-1 through B-4 in Appendix B. Specific gravity (ASTM D 854) and permeability tests (ASTM D 5084) were performed on selected samples and the results are presented on Figures B-5 and B-6. The laboratory Corrosivity tests including ph, Chloride, Sulphate and resistivity tests were performed on selected samples. The test results are presented in Appendix C and also given below. 7

12 Geotest Engineering, Inc. Report No UTMDACC Guhn Road Flood Mitigation Project November 21, Guhn Road; Houston, Texas Boring No. GB-2 GB-3 Samples Nos. S-3 S-4 Depth (ft) Soil, ph Soil Resistivity (ohm-c) 21,300 1,080 Chloride (mg/kg) Sulphate (mg/kg) Based on the corrosivity test results, the degree of corrosivity of the tested subsurface soils is negligible in terms of ph, moderate corrosive to negligible in terms of soils resistivity, threshold in terms of chloride concentration and negligible in terms of sulfate concentration. 8

13 Geotest Engineering, Inc. Report No UTMDACC Guhn Road Flood Mitigation Project November 21, Guhn Road; Houston, Texas 5.0 SITE GEOLOGY 5.1 Geologic Formation The geology of Harris County is characterized by two formations, the Lissie, located in the northwest portion of the county, and the Beaumont, located in the southeast. These formations are a part of the fluvial and marine coastal complex resulting from the glacial cycles within the Holocene/Pleistocene epoch. Northern portions of Harris County are under the influence of the drainage systems established by rivers such as the Brazos and the San Jacinto. The lithology includes silt, sand and clay with minor amounts of calcareous nodules and iron oxide, minerals that impart an acidic or alkaline characteristic to soils. Seaward the lithologies are primarily dominated by clays, often interspersed with silts and sands. The project site is located within the Lissie Formation. The upper zones of the Lissie Formation consist of clay, silt, sand and minor amounts of siliceous gravel in areas to the northwest. The Lissie Formation is characterized by a featureless flat to gently rolling surface and fluviatile deposition. The calcareous deposits and concentrations of calcium carbonate, iron oxide and iron-magnese oxides are common in the zone of weathering. 5.2 Geologic Faults in the Vicinity of Site A review of information in the Geotest library relating to known surface and subsurface geologic faults, in the general area of the project site, was undertaken. The information consisted of published reports, open file reports, and information contained in our files relating to geologic faults in this area. Based on the published documents, no faults appear to be within a 1-mile radius of the project site. The closest documented fault, White Oak Fault (part of Addicks Fault System), is about 1.7 miles north of the project site and the Long Point Fault is approximately 3 miles south of the project site. 9

14 Geotest Engineering, Inc. Report No UTMDACC Guhn Road Flood Mitigation Project November 21, Guhn Road; Houston, Texas 6.0 GENERAL SITE CONDITIONS 6.1 Existing Surface Conditions The MDACC Data Center is a single story steel framed structure with concrete tilt-up exterior wall panels. The surrounding grounds and the areas of exploration exist as relatively level concrete paved sidewalk and concrete paved parking areas, grass and planter areas. The existing grade is approximately at Elevation 85 feet. 6.2 Soil Stratigraphy Graphical representations of the major strata encountered in borings drilled along the project alignment are presented on the boring log profiles on Figures 3.1 and 3.2. To the left of each boring shown on the profile is an indication of the consistency or density of soils within each stratum. For cohesive soils, consistency is related to the undrained shear strength of the soil. Consistency of granular soils is related to the relative density of the soil. To the right of each boring shown on the profile is the USCS classification of the soil within each stratum. The symbols and abbreviations used on the boring log profiles are given on Figure 4. The existing paving, as revealed by borings GB-1 and GB-4 drilled in the pavement area, consists of 4.75 inches of concrete over 1.5 to 2 inches of brown silty sand. The top (fill) soils, as revealed by borings GB-2 and GB-3 drilled in the grass and planter areas, consist of dark gray and gray sandy silt and sandy clay with roots and calcareous nodules to a depth of about 2 feet below the existing ground surface. The subsurface soils beneath the top soils or existing paving consists of medium stiff to very stiff gray, brown and yellowish brown Sandy Clay (CL) to depths varied from 6 to 25 feet. The sandy clay has calcareous nodules encountered at various depths. The sandy clay is underlain by stiff to very stiff gray and yellowish brown or gray and reddish brown Clay (CH) to a depth of 25 feet, the maximum depth explored, in borings GB-1, GB-3 and GB-4. The clay is 10

15 Geotest Engineering, Inc. Report No UTMDACC Guhn Road Flood Mitigation Project November 21, Guhn Road; Houston, Texas slickensided and has calcareous nodules encountered at various depths. In boring GB-4, stiff dark gray Clay (CH) was encountered beneath the paving to a depth of about 4 feet. The clay is of high to very high plasticity with liquid limits ranging from 50 to 72 and plasticity indices ranging from 29 to 45. The sandy clay is of low to moderately high plasticity with liquid limits ranging from 21 to 48 and plasticity indices ranging from 6 to 32. The permeability of the sandy clay ranges from 4.3 x 10-8 to 3.4 x 10-7 cm/sec. 6.3 Groundwater Conditions Groundwater was initially encountered at depths ranging from about 11 to 18 feet below existing grade in borings GB-1 and GB-2 during the drilling operation. No groundwater was encountered during drilling operation in other borings, GB-3 and GB-4. Depth to ground water, as observed in Piezometers GB-1P and GB-3P, ranged from about 6 to 8 feet. It should be noted that groundwater levels would fluctuate with seasonal variations in rainfall and surface runoff, especially in granular soils during extended periods of heavy rainfall. 11

16 Geotest Engineering, Inc. Report No UTMDACC Guhn Road Flood Mitigation Project November 21, Guhn Road; Houston, Texas 7.0 GEOTECHNICAL ENGINEERING RECOMMENDATIONS 7.1 Flood Wall Foundation It is our understanding that due to the property lines, easements, underground utilities and existing equipment, it will be impossible to utilize the strip (or spread) footings to support the flood wall over a majority of the site. Thus, based upon these site conditions, a pier (straight drilled shaft or drilled and underreamed footing) and beam foundation system is proposed for the support of the flood wall. The proposed foundation system will consist of a shallow continuous concrete grade beam (approximately 24-inch wide and 24-inch deep) direct beneath the flood wall (top of grade beam approximately 6-inch to 9-inch below existing grade or surface) supported on either straight drilled shafts or drilled and underreamed footings placed at a depth of about 15 feet below the grade beam (approximately 18 feet below finished grade). Based on the foundation soils revealed by the soil borings, the drilled piers (straight shafts or underreamed footings, whichever is applicable) can be designed and propositioned for an allowable (net) bearing pressure as determined by the equations given below. 1, D psf, B Limit D B to 2.5 maximum 1, D psf, B Limit D B to 2.5 maximum where, = Allowable net bearing pressure for total dead and live loads in psf = Allowable net bearing pressure for dead and sustained live loads in psf D = Depth of drilled piers in feet 10 feet B = Diameter of underreamed for drilled and underreamed footing or diameter of shaft for straight drilled shaft in feet. 12

17 Geotest Engineering, Inc. Report No UTMDACC Guhn Road Flood Mitigation Project November 21, Guhn Road; Houston, Texas The drilled piers should be designed for an allowable (net) bearing pressure as determined from the above equation for total dead and live loads or dead and sustained live loads, whichever results in a larger footing area. The allowable bearing pressures contain a factor of safety of 2 for total dead and live loads and 3 for dead and sustained loads. Thus, for a 30-inch diameter drilled shaft placed at 18 feet below existing ground surface, the allowable net bearing pressure can be calculated as below. Since, Thus, D 18 B , D B 2.5 1, x 2.5 2,925 psf for total loads 1, x 2.5 1,950 psf for dead and sustained loads The allowable uplift capacity of drilled piers can be determined from the equations given below. For Straight Drilled Shafts U a = 561 d (D - 7) d 2 D For Drilled and Underreamed Footing U a = 1,021 B (D - 7) + (114 d B 2 ) D Where; U a d = Allowable uplift capacity in pounds = Diameter of shaft in feet B = Diameter of underream in feet D = Depth of drilled piers in feet 13

18 Geotest Engineering, Inc. Report No UTMDACC Guhn Road Flood Mitigation Project November 21, Guhn Road; Houston, Texas The above equations of the allowable uplift capacity include a factor of safety of 2.0 applied to the cohesion of clay soils, a factor of safety of 1.1 applied to the submerged (pier) concrete weight and a factor of safety of 1.5 applied to the submerged soil weight (above the underreamed portion). To reduce group effects, it is recommended that the piers be spaced with a minimum center to center distance of at least 2.5 times of the shaft or underreamed (bell) diameter. If drilled and underreamed footings are used, the ratio of underreamed (bell) to shaft diameter should be limited to Lateral Pressure Evaluation The cast-in-place concrete freestanding cantilever flood wall will be designed to withstand static water pressure up to an elevation of 89 feet. Current existing grade is approximately at Elevation 85 feet. There will be potentially four feet of water covering the ground surface during a flood event. An evaluation of the imposed lateral pressures should model the force imposed by the retained floodwater behind the wall. The hydrostatic pressure will be 62.4 (H w ) (psf), where H w is the maximum flood water height above the ground surface. The design equations provided on Figure 5 can be used for the design of drilled piers subject to overturning moments due to the lateral loads. 14

19 Geotest Engineering, Inc. Report No UTMDACC Guhn Road Flood Mitigation Project November 21, Guhn Road; Houston, Texas 8.0 CONSTRUCTION CONSIDERATIONS This section presents our recommendations for construction considerations for site preparation, foundation excavations, and construction monitoring for foundation. 8.1 Foundation Excavations The installation of drilled piers may require the use of temporary casing to prevent any excess of caving due to the encounter of calcareous nodules at various depths. Drilled pier excavations should be inspected by a qualified soils technician under the direction of the geotechnical engineer, prior to placement of concrete. The excavation should be checked to verify that: 1) the footing has been constructed entirely within natural clay soils having adequate bearing strength and to the specified dimensions, and that 2) excavation cuttings, and any soft, compressible materials have been removed from the bottom of the excavation. Placement of foundation concrete should be completed as soon as possible to reduce potential sloughing and caving of the foundation soils. Footings should be poured only upon the approval of the project engineer or owner's representative. 8.2 Structural Fill Requirements We recommend that soils used as structural fills to raise the grade be a low plasticity lean clay soil free of debris, and have less than five percent by weight of fibrous or organic materials. Structural fill soils should have a liquid limit less than about 40 and a plasticity index between 8 and 20. The ASTM group symbol (ASTM D 2487) for this material is CL. Representative samples of the proposed fill material should be collected, classified, tested and approved by a representative of the geotechnical engineer prior to their use, to verify if they meet the above requirements. The samples should be tested to determine the maximum dry unit weight (Standard Proctor ASTM D 698), optimum moisture content, natural moisture content, 15

20 Geotest Engineering, Inc. Report No UTMDACC Guhn Road Flood Mitigation Project November 21, Guhn Road; Houston, Texas gradation and plasticity. These tests are needed to determine if the material is acceptable as structural fill and for quality control during the compaction process. We recommend that all compacted fills be constructed by spreading the soil in loose lifts not more than eight inches in thickness. The soils should be compacted to at least 95 percent of the maximum dry density as determined by the Standard Proctor test (ASTM D 698). The moisture content of the fill soils should be maintained within minus one and plus three percentage points of the optimum moisture content as determined from the Standard Proctor test. 8.3 Groundwater Control The installation of foundation footings at this site may not require dewatering. However, if the intrusion of groundwater into drilled pier is encountered, excavations should be performed with care. If water accumulates more than 2 inches at the base of the excavation following bailing, the concrete should be tremied to the base of the excavation to prevent segregation and interference with the reinforcing steel. The tremie should be maintained at the bottom of the excavation until at least 5 feet of concrete has been placed and remain at least 5 feet below the top of the column of fluid concrete through the pour. 8.4 Construction Monitoring It is recommended that the Geotechnical Engineer be retained for testing and observation during earthwork and foundation construction phases to help verify that design requirements are fulfilled. 16

21 Geotest Engineering, Inc. Report No UTMDACC Guhn Road Flood Mitigation Project November 21, Guhn Road; Houston, Texas 9.0 PROVISIONS The description of subsurface conditions and the design information contained in this report are based on the soil borings made at the time of drilling at specific locations. Some variation in soil conditions may occur between soil borings. Should subsurface conditions be encountered which differ from those described on our boring logs, Geotest should immediately be notified so that further investigation and supplemental recommendations can be provided. The depth of the groundwater level may vary with changes in environmental conditions such as frequency and magnitude of rainfall. The stratification lines on the boring logs represent approximate boundaries between soil types. The transition between soil types, however, may be more gradual than depicted. This report has been prepared for the exclusive use of URS Corporation and the project team for design and construction of the proposed flood wall structures for MDACC Data Center Building. This report shall not be reproduced without the written permission of Geotest Engineering, Inc., URS Corporation, Walter P. Moore and Associates, or MDACC. 17

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