geotechnical exploration on fort worth …...2016/01/11 · geotechnical construction materials...

Geotechnical Construction Materials Environmental

GEOTECHNICAL EXPLORATION

on

FORT WORTH SOUTH APARTMENTS Broadway Avenue and South Calhoun Street

Fort Worth, Texas ALPHA Report No. W162304


on

FORT WORTH SOUTH APARTMENTS Broadway Avenue and South Calhoun Street

Fort Worth, Texas ALPHA Report No. W162304

Prepared for:

STONEHAWK CAPITAL PARTNERS 2215 Cedar Springs Road, Suite 1801

Dallas, TX 75201 Attention: Mr. Brandon Hopkins

November 1, 2016

Prepared By:

ALPHA TESTING, INC. 5058 Brush Creek Road Fort Worth, Texas 76119

Geotechnical Construction Materials Environmental TBPE Firm No. 813

5058 Brush Creek Road Fort Worth, Texas 76119

Tel: 817-496-5600 Fax: 817-496-5608 www.alphatesting.com

Dallas • Fort Worth • Houston • San Antonio

November 1, 2016

Stonehawk Capital Partners 2215 Cedar Springs Road, Suite 1801 Dallas, TX 75201 Attention: Mr. Brandon Hopkins

Re: Geotechnical Exploration Fort Worth South Apartments Broadway Avenue and South Calhoun Street Fort Worth, Texas ALPHA Report No. W162304

Attached is the report of the geotechnical exploration performed for the project referenced above. This study was authorized by Mr. Brandon Hopkins on September 14, 2016 and performed in accordance with ALPHA Proposal No. 54899 dated September 12, 2016.

This report contains results of field explorations and laboratory testing and an engineering interpretation of these with respect to available project characteristics. The results and analyses were used to develop recommendations to aid design and construction of foundations and pavement.

ALPHA TESTING, INC. appreciates the opportunity to be of service on this project. If we can be of further assistance, such as providing materials testing services during construction, please contact our office.

Sincerely,

ALPHA TESTING, INC.

Jeromi C. Kelsey, E.I.T. Geotechnical Project Manager

November 1, 2016 Brian J. Hoyt, P.E. Geotechnical Department Manager

JCK/BJH/rl Copies: (1-PDF) Client

TABLE OF CONTENTS

On

ALPHA REPORT NO. W162304

PURPOSE AND SCOPE .................................................................................................... 1 PROJECT CHARACTERISTICS ...................................................................................... 1 FIELD EXPLORATION .................................................................................................... 2 LABORATORY TESTS .................................................................................................... 3 GENERAL SUBSURFACE CONDITIONS ...................................................................... 3 DESIGN RECOMMENDATIONS .................................................................................... 4 6.1 Existing Structures and Fill ..................................................................................... 4 6.2 Potential Seasonal Movements and Subgrade Improvements ................................ 5

6.2.1 Subgrade Improvement Utilizing Moisture Conditioning .......................... 6 6.2.2 Subgrade Improvement for Pool Area ........................................................ 8

6.3 Slab-on-Grade Foundations .................................................................................... 8 6.4 Post-Tensioning Institute, Design of Post-Tensioned Slab-on-Grade .................... 8 6.5 Drilled, Straight-Shaft Piers for Parking Deck ....................................................... 9 6.6 Drilled and Underreamed Piers for Parking Deck (Alternative) .......................... 10 6.7 Exterior Flatwork .................................................................................................. 12 6.8 Seismic Considerations ......................................................................................... 12 6.9 Pavement ............................................................................................................... 12

6.9.1 Pavement Subgrade Preparation ................................................................ 13 6.9.2 Portland-Cement Concrete Pavement ....................................................... 13 6.9.3 Asphalt Concrete Pavement ...................................................................... 14 6.9.4 Ground Level Paving for Parking Deck .................................................... 15

6.10 Drainage and Other Considerations ...................................................................... 15 GENERAL CONSTRUCTION PROCEDURES AND RECOMMENDATIONS .......... 16 7.1 Site Preparation and Grading ................................................................................ 16 7.2 Foundation Excavations ........................................................................................ 18 7.3 Fill Compaction .................................................................................................... 19 7.4 Groundwater ......................................................................................................... 20 LIMITATIONS ................................................................................................................. 21

APPENDIX

A-1 Methods of Field Exploration Boring Location Plan – Figure 1

B-1 Methods of Laboratory Testing Swell Test Results – Figure 2 Logs of Borings Key to Soil Symbols and Classifications

ALPHA Report No. W162304

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PURPOSE AND SCOPE The purpose of this geotechnical exploration is for ALPHA TESTING, INC. (“ALPHA”) to evaluate for the “Client” some of the physical and engineering properties of subsurface materials at selected locations on the subject site with respect to formulation of appropriate geotechnical design parameters for the proposed construction. The field exploration was accomplished by securing subsurface samples from widely spaced test borings performed across the expanse of the site. Engineering analyses were performed from results of the field exploration and results of laboratory tests performed on representative samples. Also included are general comments pertaining to reasonably anticipated construction problems and recommendations concerning earthwork and quality control testing during construction. This information can be used to evaluate subsurface conditions and to aid in ascertaining construction meets project specifications. Recommendations provided in this report were developed from information obtained in test borings depicting subsurface conditions only at the specific boring locations and at the particular time designated on the logs. Subsurface conditions at other locations may differ from those observed at the boring locations, and subsurface conditions at boring locations may vary at different times of the year. The scope of work may not fully define the variability of subsurface materials and conditions that are present on the site. The nature and extent of variations between borings may not become evident until construction. If significant variations then appear evident, our office should be contacted to re-evaluate our recommendations after performing on-site observations and possibly other tests.

PROJECT CHARACTERISTICS It is proposed to construct a new four to five level apartment building on a site generally located south of East Broadway Avenue and east of Crawford Street in Fort Worth, Texas. The proposed construction also includes a single level above-grade parking deck, four (4) townhome clusters, 16 detached parking garages [four (4) spaces in each of four (4) separate garage buildings] and a swimming pool. A drawing illustrating the general outline of the property is provided as Figure 1, the Boring Location Plan, in the Appendix of this report. At the time the field exploration was performed, the site generally consisted of a previously developed city block which was mostly cleared. Some buildings and associated paved parking and drive areas were observed on the site. We understand that these structures will be demolished prior to new construction. Review of topographical maps available at www.dfwmaps.com indicates the site generally slopes down to the northeast about 28 ft (Approximate Elevation: 650 ft to Approximate Elevation 522 ft). Grading plans were not available at the time of this study. For the purpose of our analysis, we have assumed maximum cuts and fills of 2 ft will be required to achieve final grade in the building pad areas.


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We understand the apartment building and townhome clusters will be supported with slab foundations designed for potential seasonal movements of about 1, 2 or 3 inches. We expect the parking deck will be supported with drilled piers. The ground level below the parking deck will be designed as typical site pavement for parking and drives. Table A below contains a summary of the project characteristics.

TABLE A: Proposed Structures, Characteristics and Anticipated Foundation Systems

Structure Building Characteristics Anticipated Foundation

System

Parking Deck Single level above-grade parking deck Drilled Piers

Detached parking garages

Four (4) detached single-story garage buildings consisting of four (4) parking spaces each

Post-tensioned slab-on-grade

foundation

Apartment Buildings

Four to five level wood-framed or steel framed apartment building

Post-tensioned slab-on-grade

foundation

We further understand pavement for the project will consist of either Portland-cement concrete (PCC) or asphalt concrete (AC).

FIELD EXPLORATION Subsurface conditions on the site were explored by drilling a total of twelve (12) widely spaced test borings. Eight (8) test borings were drilled to a depth of about 20 ft each, two (2) test borings were drilled to a depth of about 30 ft each and two (2) test borings were drilled to a depth of about 35 ft each. All test borings were performed in general accordance with ASTM D 420 using standard rotary drilling equipment. The approximate location of each boring is shown on the Boring Location Plan, Figure 1, enclosed in the Appendix of this report. Details of drilling and sampling operations are briefly summarized in Methods of Field Exploration, Section A-1 of the Appendix Subsurface types encountered during the field exploration are presented on the Log of Boring sheets (boring logs) included in the Appendix of this report. The boring logs contain our Field Technician's and Engineer's interpretation of conditions believed to exist between actual samples retrieved. Therefore, the boring logs contain both factual and interpretive information. Lines delineating subsurface strata on the boring logs are approximate and the actual transition between strata may be gradual.


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LABORATORY TESTS Selected samples of the subsurface materials were tested in the laboratory to evaluate their engineering properties as a basis in providing recommendations for foundation design and earthwork construction. A brief description of testing procedures used in the laboratory can be found in Methods of Laboratory Testing, Section B-1 of the Appendix. Individual test results are presented on the Log of Boring sheets or summary data sheets enclosed in the Appendix.

GENERAL SUBSURFACE CONDITIONS Based on geological atlas maps available from the Bureau of Economic Geology, published by the University of Texas at Austin, the project site lies within the Pawpaw Formation, Weno Limestone, and Denton Clay formations mapped as undivided. This undivided formation generally consists of limestone and marl (limey shale) with residual clay overburden soils characterized by moderate to high shrink-swell potential. Subsurface conditions encountered in Borings 2, 4, 5, 7, 9, 10 and 11 generally consisted of about 2 ft to 8 ft of sandy clay, gravelly clay and/or clayey gravel fill underlain by clay and/or shaly clay soils to depths of about 12 ft to 22 ft below the ground surface. Limestone was then encountered which extended to the 20 ft to 35 ft respective termination depth of the borings. The upper 2 ft of limestone (at a depth of about 20 ft to 22 ft) encountered in Boring 7 was tan and the limestone encountered at a depth of about 17 ft which extended to the 20 ft termination depth in Boring 10 was tan. The remaining limestone encountered in these borings was gray. Subsurface conditions encountered in the remaining borings (Borings 1, 3, 6, 8 and 12) generally consisted of about 2 ft to 12 ft of clay and gravelly clay fill/possible fill underlain by clay and/or shaly clay soils to the 20 ft termination depth of the borings. Some of the samples of existing fill material retrieved from the borings were observed to contain construction debris consisting of concrete and brick fragments. About 2 inches of asphalt pavement was encountered at the surface in Borings 5 and 9. About 4 inches of concrete pavement was encountered at the surface in Boring 2. More detailed stratigraphic information is presented on the Log of Borings sheets attached to this report. The granular materials (clayey sand) encountered in the Borings 7 are considered relatively permeable and are anticipated to have a relatively rapid response to water movement. However, the gravelly clay, sandy clay, clay, shaly clay and limestone materials encountered in the borings are considered relatively impermeable and are expected to have a relatively slow response to water movement. Therefore, several days of observation would be required to evaluate actual groundwater levels within the depths explored. Also, the groundwater level at the subject site is expected to fluctuate seasonally depending on the amount of rainfall, prevailing weather conditions, and subsurface drainage characteristics. Groundwater was encountered on drilling tools during drilling at depths of about 3 ft to 8 ft below the ground surface in Borings 2, 7 and 11. Groundwater was not observed in the open boreholes immediately upon completion of drilling or in the remaining borings. However, it is common to encounter seasonal groundwater in fill and granular materials, from natural fractures within the clayey matrix, at the soil/rock (limestone) interface or from fractures in the rock, particularly during or after periods of precipitation. If more detailed groundwater information is required, monitoring wells or piezometers can be installed.


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Further and more detailed information concerning subsurface materials and conditions encountered can be obtained from the boring logs provided in the Appendix of this report.

DESIGN RECOMMENDATIONS The following design recommendations were developed on the basis of the previously described Project Characteristics (Section 2.0) and General Subsurface Conditions (Section 5.0). If project criteria should change, including the building locations on the site our office should conduct a review to determine if modifications to the recommendations are required. Further, it is recommended our office be provided with a copy of the final plans and specifications for review prior to construction. Design criteria given in this report were developed assuming the floor slabs are constructed within 2 ft of existing grade. Cutting and filling on the site more than 2 ft can alter the recommended foundation design parameters. Therefore, it is recommended our office be contacted before performing cutting and filling more than 2 ft on site to verify appropriate design parameters are utilized for final foundation design. Slab foundations can be utilized for support of the proposed apartment building, townhomes and detached garage buildings provided some movement in the foundations is acceptable. Subgrade improvement will be required to reduce seasonal movements to the desired levels of about 1, 2 or 3 inches. If foundation movement is not acceptable, it will be necessary to support the buildings on drilled pier foundations with a structurally suspended slab.

6.1 Existing Structures and Fill As discussed in Section 5.0, existing fill and possible fill was encountered to depths of about 2 ft to 12 ft below the ground surface in the borings. If compaction records for this fill cannot be obtained, the existing fill should be considered uncontrolled fill. Uncontrolled fill is generally not considered suitable for support of slab foundations or swimming pools. Any existing uncontrolled fill should be removed from the building pad and swimming pool areas, and replaced with engineered fill in accordance with the recommendations in Section 6.2 or Section 7.3 as applicable. The excavated materials may be suitable for reuse as engineered fill in the building pad areas provided they are free of organics, boulders, rubble, and other debris. Construction debris consisting of concrete, asphalt and brick fragments were encountered in the borings. Although not encountered in the borings, fill material could also contain organics, boulders, rubble and other debris which could be encountered during site grading and general excavation. The earthwork and excavation contracts should contain provision for sorting and/or removal of unsuitable materials and excavation of possible obstructions in the existing fill. The lateral extent and depth and nature of the fill are not known. Test pits could be performed prior to construction to verify the lateral extent, depth, and nature of the fill materials. ALPHA would be pleased to provide this service if desired.


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Please note; even if fill is properly compacted as recommended in Section 6.2 or Section 7.3 of this report, fills in excess of about 10 ft to 12 ft are still subject to settlements over time of up to about 1 to 2 percent of the total fill thickness. This should be considered when removing and re-compacting existing onsite fills. We understand the existing structures and pavement will be removed prior to new construction. Any areas disturbed during removal of the existing or previously removed structures within the proposed building and swimming pool areas should be re-compacted under moisture-density compaction control as discussed in Section 7.3 of this report, below. All foundation elements of the existing structures should be removed or cut off at least 1 ft below finished grade or 1 ft below the new structural elements, whichever is deeper. All abandoned utility lines should be either removed or positively sealed to prevent possible water seepage into the subsurface clay materials. 6.2 Potential Seasonal Movements and Subgrade Improvements Our findings indicate slab-on-grade foundations and the grade supported pavement below the parking deck (and any other grade supported pavement or structures on the site) constructed within 2 ft of the existing ground surface could experience post construction seasonal movements of up to about 5 inches due to shrinking and swelling of active clay soils. In addition, grade supported structures constructed over uncontrolled fill are subject to indeterminate levels of settlement. The above potential seasonal movement was estimated in general accordance with methods outlined by Texas Department of Transportation (TxDOT) Test Method Tex-124-E, from results of absorption swell tests, and engineering judgment and experience. Estimated movements were calculated assuming the moisture content of the in-situ soil within the normal zone of seasonal moisture content change varies between a "dry" condition and a "wet" condition as defined by Tex-124-E. Also, it was assumed a 1 psi surcharge load from the floor slabs acts on the subgrade soils. Movements exceeding those predicted above could occur if positive drainage of surface water is not maintained or if soils are subject to an outside water source, such as leakage from a utility line or subsurface moisture migration from off-site locations.

We understand it is desired to reduce the potential seasonal movements of the slab foundations to about 1, 2 or 3 inches. Subgrade improvement consisting of moisture conditioning the onsite soils in conjunction with a possible non-expansive fill cap (where applicable) will be required to reduce potential seasonal movements. Table B below summarize the required depths of subgrade improvement to reduce the potential seasonal movements to the corresponding levels of 1, 2 or 3 inches.

Table B: Subgrade Improvement Summary Desired Level of Potential

Seasonal Movements (inches)

Required Thickness of Non-Expansive Fill Cap

(ft)

Required Depth of Moisture Conditioning

(ft) 3 None 8 2 None 10 1 2 10


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Considering the presence of uncontrolled fill material requiring removal and replacement, water pressure injection is not considered practical for this site. Our office should be contacted if water pressure injection recommendations are desired. In choosing moisture conditioning as a method potential soil movement reduction, the Client is accepting some post construction movement of grade supported structures (about 1, 2 or 3 inches depending on the selected improvement from Table B). Therefore, the Client understands and acknowledges that in the geographical region covered by this report, potential movements of 1, 2 or 3 inches is considered a reasonable compromise between foundation design, construction cost and the amount of allowable movement of the foundation.

6.2.1 Subgrade Improvement Utilizing Moisture Conditioning Movement of the slab foundations could be reduced to about 1 inch by placing at least 2 ft of non-expansive material between the bottom of the floor slab and the top surface of moisture-conditioned soil extending to a depth of 10 ft below the non-expansive fill as denoted in Table B above. As an alternative, movement of the slab foundations could be reduced to about 2 inches or 3 inches by placing moisture conditioned soils to depths of 10 ft and 8 ft below the floor slabs, respectively, as summarized in Table B above. Non-expansive material could consist of select fill or flexible base material as discussed in Section 7.3 of this report. Moisture-conditioning consists of over-excavating the site soils, then processing and compacting the specified minimum thickness of soil at a “target” moisture content approximated to be at least 5 percentage points above the material’s optimum moisture content as determined by the standard Proctor method (ASTM D 698). Some of the onsite soils with a relatively lower plasticity index may require compaction at a moisture content closer to optimum. Any deviation from the required minimum 5 percentage points above optimum should be verified by ALPHA during construction. The moisture-conditioned soil, free of debris and any rock fragment greater than 4 inches, should be placed in about 8-inch thick loose lifts and compacted to a dry density of 93 to 97 percent of standard Proctor maximum dry density. Moisture conditioning of the on-site soil should extend throughout the entire building pad area and at least 5 ft beyond the perimeter of the building. At building entrances and outward swinging doors, moisture conditioning should extend at least 10 ft beyond the building perimeter. However, non-expansive material should not extend beyond the building limits. If flatwork or paving is not planned adjacent to the structure (i.e. above the moisture-conditioned soils), a moisture barrier consisting of a minimum of 10 mil plastic sheeting with 8 to 12 inches of soil cover should be provided above the moisture conditioned soils. Moisture-conditioned soils should be maintained in a moist condition prior to placement of the required thickness of non-expansive material or flatwork.


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In areas where select, non-expansive fill is not used, plastic sheeting (minimum 6 mil thickness polyethylene) should be placed above the moisture-conditioned soil within one (1) week after completion of improvement for long-term maintenance of the moisture content of the moisture-conditioned soil. The moisture-conditioned soils should not be allowed to dry prior to placement of the plastic sheeting. This plastic sheeting should be placed 8 to 12 inches below final grade and should also extend at least 5 ft beyond the perimeter of the structure. Clay soil covering should be provided over the plastic sheeting to protect the plastic long-term from deterioration due to exposure to sunlight. The use of sandy soils (soil with a plasticity index less than 20) above the plastic should be avoided. Following completion of moisture conditioning and placement of the plastic sheeting as described above, estimated potential seasonal movements should not exceed the movements estimated in Table B for the respective improvement. If construction of the floor slabs will occur immediately following moisture conditioning, plastic sheeting may not be required provided the soils are kept moist through periodic watering. Alpha should observe and verify that soils are kept moist in areas where plastic sheeting is not placed. However, the plastic sheeting extending 5 ft past the building perimeter will still be required where flatwork is not present, as discussed above. Vapor barriers should still be used where floors sensitive to moisture are present. The resulting estimated potential seasonal movements (about 1, 2 or 3 inches depending on the selected improvement depth) were calculated assuming the moisture content of the moisture-conditioned soil varies between the “target” moisture content and the “wet” condition while the deeper undisturbed in-situ soil within the normal zone of seasonal moisture content change varies between the "dry" condition and the "wet" condition as defined by methods outlined in TxDOT Test Method Tex-124-E. Please note, it is the intent of the moisture-conditioning process described above to reduce the free swell potential of the moisture-conditioned soil to 1 percent or less. Additional laboratory tests (i.e., standard Proctors, absorption swell tests, etc.) should be conducted during construction to verify the “target” moisture content for moisture-conditioning (estimated at 5 percentage points above the material’s optimum moisture content as defined by ASTM D 698) is sufficient to reduce the free swell potential of the processed soil to 1 percent or less. In addition, it is recommended samples of the moisture-conditioned material be routinely obtained during construction to verify the free swell of the improved material is 1 percent or less. Installation of moisture-conditioned clays should be monitored and tested on a full-time basis by a representative of ALPHA to verify the soils tested were placed with the proper lift thickness, moisture content, and degree of compaction.


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6.2.2 Subgrade Improvement for Pool Area We understand it is desired to reduce potential movements of the swimming pool to about 1 inch. Potential movements in the pool area could be reduced to about 1 inch by utilizing a 2 ft cap of non-expansive fill in conjunction with 10 ft of moisture conditioning similar to that discussed for slab foundations above. The elevation of the subgrade treatment for the swimming pool should match that of the surrounding deck areas. For example, where the pool is 1 ft deep, the underlying subgrade treatment should consist of 1 ft of non-expansive fill over 10 ft of moisture conditioning. Likewise, where the pool is 4 ft deep, the underlying subgrade treatment should consist of 8 ft of moisture conditioned soils. Moisture conditioned soils to a depth of 10 ft can be installed in the same manner as described in 6.2.1 above. The moisture conditioned soils should extend at least 5 ft beyond the pool area. The portion of the moisture conditioned soils extending past the pool should be covered with 6 to 8 mil plastic sheeting similar to that discussed in Section 6.2.1 above. Non expansive fill could consist of select fill or flexible base material as described in Section 7.3 below.

6.3 Slab-on-Grade Foundations Slab foundations constructed within 2 ft of the existing ground surface could be subject to about 5 inches of post construction seasonal movements as discussed in Section 6.2. Subgrade improvement as discussed in Section 6.2 can be utilized to reduce potential seasonal movements of slab foundations. The slab foundations should be designed with exterior and interior grade beams adequate to provide sufficient rigidity to the foundation system. A net allowable soil bearing pressure of 1.5 kips per sq ft may be used for design of all grade beams bearing on a moisture-improved subgrade as described above in Section 6.2 of this report. Grade beams should bear a minimum depth of 18 inches below final grade and should have a minimum width of 10 inches for bearing capacity considerations. To reduce cracking as normal movements occur in foundation soils, all grade beams and floor slabs should be adequately reinforced. It is common to experience some minor cosmetic distress to structures with slab-on-grade foundation systems due to normal ground movements. A properly designed and constructed moisture barrier should be placed between the slab and subgrade soils to retard moisture migration through the slabs. 6.4 Post-Tensioning Institute, Design of Post-Tensioned Slab-on-Grade Provided below is information for the design of post-tensioned, slab-on-grade foundation. Design parameters provided below were evaluated based on the conditions encountered in the borings and using information and correlations published by PTI Third Edition and VOLFLO 1.5 computer program provided by Geostructural Tool Kit, Inc. (GTI).


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TABLE C PTI Design Parameters

Potential Seasonal Movement = 3 inches (After Subgrade Improvement as Described in Section 6.2 Above)

EDGE LIFT CENTER LIFT

Edge Moisture Distance (em), ft 3.9 7.5

Differential Soil Movement (ym), inches 2.0 (swell) 1.4 (shrink)

TABLE D

PTI Design Parameters Potential Seasonal Movement = 2 inches

(After subgrade improvements as discussed in Section 6.1)




TABLE E

PTI Design Parameters Potential Seasonal Movement = 1 inch

(After subgrade improvements as discussed in Section 6.1)




6.5 Drilled, Straight-Shaft Piers for Parking Deck

Our findings indicate the proposed parking deck could be supported using a system of drilled, straight-shaft piers bearing at least 3 ft into competent tan or gray limestone. Limestone was encountered at depths of about 20 ft to 22 ft below the existing ground surface in Borings 2, 4, 5 and 7 drilled in the parking deck area. Table F below contains a summary of recommended allowable end bearing pressures and skin friction values.

Table F: Allowable End Bearing Pressures and Skin Friction Values

Bearing Stratum End

Bearing (ksf)

Allowable Skin Friction in

Compression (ksf)

Allowable Skin Friction in Uplift

Resistance (ksf)

At least 3 ft into Clay Shale

N/A 2 1.6

At least 2 ft into Tan or Gray Limestone

35 5.0 4.5


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Please note; a distance of at least two (2) pier shaft diameters should be provided between the bottom of the pier and the bottom of the deepest test boring (35 ft). If this minimum clearance between the bottom of the pier and the bottom of the deepest test boring is not provided, the pier should be designed strictly as a friction pier, neglecting end bearing. Drilled piers designed as friction piers should not bear at a depth greater than 35 ft below the existing ground surface. Deeper borings could be drilled if deeper drilled shafts are required. The skin friction component should be applied only to the portion of the shaft located in the limestone, neglecting the upper 3 ft of limestone and the portion above the bottom of any temporary casing. The minimum clear spacing between piers should be at least two (2) pier shaft diameters, based on the larger pier, to develop the full load carrying capacity from skin friction. The above bearing pressure contains a factor of safety of at least three (3) considering a general bearing capacity failure and the skin friction value has a factor of safety of at least two (2). Normal elastic settlement of piers under loading is estimated at less than about ½ inch. Each pier should be sufficiently embedded into limestone and designed with full length reinforcing steel to resist the uplift pressure (soil-to-pier adhesion) due to potential soil swell along the shaft from post construction heave and other uplift forces applied by structural loadings. The magnitude of uplift adhesion due to soil swell along the pier shaft cannot be defined accurately and can vary according to the actual in-place moisture content of the soils during construction. It is estimated the average uplift adhesion will not exceed about 2.2 kips per sq ft. This soil adhesion is approximated to act uniformly over the upper 12 ft of the pier shaft in contact with clay soils. The uplift adhesion due to soil swell can be neglected over the portion of the shaft in contact with any non-expansive material used in the building pad or any limestone. All grade beams connecting piers should be formed and not cast in earthen trenches. Grade beams should be formed with a nominal 8-inch void at the bottom. Commercially available cardboard box forms (cartons) are made for this purpose. The cardboard cartons should extend the full length and width of the grade beams. Prior to concrete placement, cartons should be inspected to verify they are firm, properly placed, and capable of supporting wet concrete. Some type of permanent soil retainer, such as pre-cast concrete panels, must be provided to prevent soils adjacent to grade beams from sloughing into the void space at the bottom of the grade beams. Additionally, backfill soils placed adjacent to grade beams must be compacted as outlined in Section 7.3 of this report. 6.6 Drilled and Underreamed Piers for Parking Deck (Alternative) Our findings indicate the parking deck could be supported using a system of drilled and underreamed piers. It is recommended these piers bear in clay or shaly clay at a depth of at least 17 ft below existing grade as encountered during drilling. Some field adjustments in the depth of the piers may be required in some areas to maintain the bottom of the piers above any possible groundwater seepage encountered near the bearing depth.


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Adjustments in the depths of the piers should be observed in the field by ALPHA personnel. Also, the underream portion of the pier should bear sufficiently deep that the entire underream is situated below the depth of any planned or existing fill. Please note: As discussed above and in Section 5.0 sandy clays/clayey sands were encountered in the test borings above the bearing depth. These granular materials are prone to caving or sloughing, particular during wet weather periods and when forming the bell for underreamed piers. In addition, groundwater was encountered in one of the borings at a depth of 8 ft below existing grade which may require the use of casing during pier drilling. It is recommended a test pier be performed outside the building pad area (or within the building pad area between designated pier locations) to verify the constructability of underreams at this site and/or the required use of casing (also see Section 7.2). We should be contacted for additional recommendations if underream collapse occurs. Piers can be dimensioned using a net allowable end bearing pressure of 4.5 kips per sq ft and no skin friction component of resistance. The above bearing pressure contains a factor of safety of at least three (3) considering a general bearing capacity failure. Normal elastic settlement of piers under loading is estimated to be less than about 1 inch. Each pier should be designed with full length reinforcing steel to resist the uplift pressure (soil-to-pier adhesion) due to potential soil swell along the shaft from post construction heave and other uplift forces applied by structural loadings. The magnitude of uplift adhesion due to soil swell along the pier shaft cannot be defined accurately and can vary according to the actual in-place moisture content of the soils during construction. It is estimated this uplift adhesion will not exceed about 2.2 kips per sq ft. This soil adhesion is approximated to act uniformly over the upper 12 ft of the pier shaft in contact with clayey soils. Uplift adhesion due to soil heave can be neglected over the portion of the pier shaft in contact with any non-expansive material. The uplift force due to swelling of active clays should be resisted by the underreamed portion of the pier. The underreamed portion should be at least two (2) and not exceeding three (3) times the diameter of the shaft. The minimum clear spacing between edges of adjacent piers should be at least one (1) underream diameter, based on the larger underream.

All grade beams connecting piers should be formed and not cast in earthen trenches. Grade beams should be formed with a nominal 8-inch void at the bottom. Commercially available cardboard box forms (cartons) are made for this purpose. The cardboard cartons should extend the full length and width of the grade beams. Prior to concrete placement, the cartons should be inspected to verify they are firm, properly placed, and capable of supporting wet concrete. Some type of permanent soil retainer, such as pre-cast concrete panels, must be provided to prevent soils adjacent to grade beams from sloughing into the void space at the bottom of the grade beams. Additionally, backfill soils placed adjacent to grade beams must be compacted as outlined in Section 7.3 of this report.


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6.7 Exterior Flatwork

Exterior flatwork supported within 2 ft of existing grade could be subjected to potential seasonal movements of up to about 5 inches as described in Section 6.2. In areas where flatwork movement is critical (such as, but not limited to, main entrances), subgrade improvement as discussed in Section 6.2.1 can be considered to reduce the potential soil movement. 6.8 Seismic Considerations The Site Class for seismic design is based on several factors that include soil profile (soil or rock), shear wave velocity, and strength, averaged over a depth of 100 ft. Since our borings did not extend to 100-foot depths, we based our determinations on the assumption that the subsurface materials below the bottom of the borings were similar to those encountered at the termination depth. Based on Section 1613.3.2 of the 2012 International Building Code and Table 20.3-1 in the 2010 ASCE-7, we recommend using Site Class C (very dense soil and soft rock) for seismic design at this site 6.9 Pavement To permit correlation between information from test borings and actual subgrade conditions exposed during construction, a qualified Geotechnical Engineer should be retained to provide subgrade monitoring and testing during construction. If there is any change in project criteria, the recommendations contained in this report should be reviewed by our office. Calculations used to determine the required pavement thickness are based only on the physical and engineering properties of the materials used and conventional thickness determination procedures. Pavement joining buildings should be constructed with a curb and the joint between the building and curb should be sealed. Related civil design factors such as subgrade drainage, shoulder support, cross-sectional configurations, surface elevations, reinforcing steel, joint design and environmental factors will significantly affect the service life and must be included in preparation of the construction drawings and specifications, but all were not included in the scope of this study. Normal periodic maintenance will be required for all pavements to achieve the design life of the pavement system. Recommendations for Portland cement concrete (PCC) and asphalt concrete (AC) pavement are provided below. These types of pavement are not considered equal in performance. Asphalt concrete pavement should be expected to have more frequent and higher maintenance costs. Also, pavement in dumpster areas and areas receiving heavy truck traffic should consist of PCC. 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 minimum standards for pavement section construction may exceed those provided.


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As discussed, existing fill was observed to depths of up to 12 ft below the ground surface in the borings. Pavement supported on uncontrolled fill is subject to indeterminate levels of settlement. In many cases, the Client can accept this risk since pavement can tolerate higher degrees of movement than building structures and is more easily repaired. However if indeterminate levels of pavement settlement are not acceptable, it would be required to re-compact all existing fill below pavement areas. A reasonable compromise could include re-compacting the upper 3 ft of subgrade soils below the pavement to provide uniform subgrade support. However, the risk of indeterminate settlements would still exist for the portion of uncontrolled fill remaining below the upper 3 ft. In particular, the surface parking area below the parking deck should consider the potential for indeterminate levels of settlement during design.

6.9.1 Pavement Subgrade Preparation In areas where clay soils are exposed after final subgrade elevation is achieved, the exposed surface of the pavement subgrade soil should be scarified to a depth of 6 inches and mixed with a minimum 7 percent hydrated lime (by dry soil weight) in conformance with TxDOT Standard Specification Item 260. Assuming an in-place unit weight of 100 pcf for the pavement subgrade soils, this percentage of lime equates to about 32 lbs of lime per sq yard of treated subgrade. The actual amount of lime required should be confirmed by additional laboratory tests (ASTM C 977 Appendix XI) prior to construction. The soil-lime mixture should be compacted to at least 95 percent of standard Proctor maximum dry density (ASTM D 698) and within the range of 0 to 4 percentage points above the mixture's optimum moisture content. In all areas where hydrated lime is used to stabilize subgrade soil, routine Atterberg-limit tests should be performed to verify the resulting plasticity index of the soil-lime mixture is at/or below 15. We recommend subgrade improvement procedures extend at least 1 ft beyond the edge of the pavement to reduce effects of seasonal shrinking and swelling upon the extreme edges of pavement. Improvement of the pavement subgrade soil will not prevent normal seasonal movement of the underlying untreated materials. Pavement and other flatwork will have the same potential for movement as slabs constructed directly on the existing undisturbed soils. Therefore, good perimeter surface drainage with a minimum slope of 2 percent away from the pavement is recommended. The use of sand as a leveling course below pavement supported on expansive clays should be avoided. Normal maintenance of pavement should be expected over the life of the structures. 6.9.2 Portland-Cement Concrete Pavement

Lime treatment of the clay pavement subgrade as described in Section 6.9.1 above is recommended for drive lanes, fire lanes, and pavement subject to truck and dumpster traffic. Lime treatment of the pavement subgrade is not necessary for PCC pavements subjected exclusively to passenger vehicle traffic, although lime treatment in these areas would be generally beneficial to the long-term


14

performance of the pavement. Prior to construction of pavement on untreated clay subgrade soil, the exposed subgrade should be scarified to a depth of at least 6 inches and compacted to at least 95 percent of standard Proctor maximum dry density (ASTM D 698) and within the range of 0 to 4 percentage points above the material's optimum moisture content. Pavement subjected exclusively to passenger vehicle traffic can then consist of 5 inches of adequately reinforced PCC. A minimum of 6 inches PCC is recommended in drive lanes, fire lanes and areas subject to light volume truck traffic. A minimum of 7 inches of PCC is recommended for dumpster traffic areas or pavement subject to moderate volume truck traffic. Portland-cement concrete should have a minimum compressive strength of 3,000 lbs per sq inch (psi) at 28 days in light-duty traffic areas and 3,500 psi in moderate-duty and truck traffic areas. Concrete should be designed with 5 + 1 percent entrained air. Joints in concrete paving should not exceed 15 ft. Reinforcing steel should consist of No. 3 bars placed at 18 inches on-center in two directions. Alternately, lime-stabilization of the clay pavement subgrade could be eliminated by increasing the corresponding PCC thickness presented in the pavement sections above for drive lanes, fire lanes, and pavement subjected to truck and dumpster traffic by 1 inch. Prior to construction of pavement on untreated clay subgrade soil, the exposed subgrade should be scarified to a depth of at least 6 inches and compacted to at least 95 percent of standard Proctor maximum dry density (ASTM D 698) and within the range of 0 to 4 percentage points above the material's optimum moisture content. 6.9.3 Asphalt Concrete Pavement

Subgrade preparation as described in Section 6.9.1 above is required for asphalt concrete pavement.

1. In light-duty traffic areas (passenger vehicle parking and areas up to about

100,000 18-kip equivalent axle load repetitions), the pavement section can consist of at least 5 inches of asphalt concrete. This section could be composed of 2 inches of surface course (TxDOT Standard Specification Item 340 – Type D Surface Course) over 3 inches of asphalt concrete base course (TxDOT Standard Specification Item 340 – Type A or B Base Course) and overlying a lime-treated subgrade prepared as recommended in Section 6.9.1.

2. In moderate-duty traffic areas (drive lanes, bus lanes, and areas up to about

300,000 18-kip equivalent axle load repetitions), the pavement section can consist of at least 6 inches of asphalt concrete. This section could be composed of 2 inches of surface course (TxDOT Standard Specification Item 340 – Type D Surface Course) over 4 inches of asphalt concrete base course (TxDOT Standard Specification Item 340 – Type A or B Base Course) and overlying a lime-treated subgrade prepared as recommended in Section 6.9.1.


15

The coarse aggregate in the surface course should be composed of angular crushed limestone rather than smooth gravel. 6.9.4 Ground Level Paving for Parking Deck The ground level pavement below the parking deck could experience post construction seasonal movement of up to about 5 inches due to shrinking and swelling of active clay soils as discussed in Section 6.2. Overhead clearance for the parking deck should take this level of movement (or resulting level of movement after subgrade improvement) into consideration during design. In addition, indeterminate levels of settlement can occur with floor slabs or paving supported on uncontrolled fill. Subgrade improvement as recommended in Section 6.2 can be used to reduce potential seasonal movements of the ground level parking for the parking deck. If moisture conditioning is performed below the ground level parking deck pavement, pavement should consist exclusively of PCC. Lime stabilization of the upper 6 inches will still be required where moisture conditioning is used to reduce potential movements to about 2 or 3 inches. If potential movements in the parking deck area are reduced to about 1 inch by placing a 2 ft cap of non-expansive fill over 10 ft of moisture conditioned soils, lime stabilization of the upper 6 inches is not required.

6.10 Drainage and Other Considerations Adequate drainage should be provided to reduce seasonal variations in the moisture content of foundation soils. All pavement and sidewalks within 5 ft of the structures should be sloped away from the buildings to prevent ponding of water around the buildings. Final grades within 5 ft of the structures should be adjusted to slope away from the structures at a minimum slope of 2 percent. These drainage precautions should be observed in the pool area as well. Maintaining positive surface drainage throughout the life of the structures is essential. In areas with pavement or sidewalks adjacent to the new structures, a positive seal must be maintained between the structure and the pavement or sidewalk to minimize seepage of water into the underlying supporting soils. Post-construction movement of pavement and flatwork is common. Normal maintenance should include examination of all joints in paving and sidewalks, etc. as well as resealing where necessary. Several factors relate to civil and architectural design and/or maintenance, which can significantly affect future movements of the foundation and floor slab system:

1. Preferably, a complete system of gutters and downspouts should carry runoff water a minimum of 5 feet from the completed structures.

2. Large trees and shrubs should not be allowed closer to the foundations

than a horizontal distance equal to roughly one-half of their mature height due to their significant moisture demand upon maturing.


16

3. Moisture conditions should be maintained "constant" around the edge of the slabs. Ponding of water in planters, in unpaved areas, and around joints in paving and sidewalks can cause slab movements beyond those predicted in this report.

4. Planter box structures placed adjacent to the buildings should be provided

with a means to assure concentrations of water are not available to the subsoil stratigraphy.

Trench backfill for utilities should be properly placed and compacted as outlined in Section 7.3 of this report and in accordance with requirements of local City standards. Since granular bedding backfill is used for most utility lines, the backfilled trench should not become a conduit and allow access for surface or subsurface water to travel toward the new structures. Concrete cut-off collars or clay plugs should be provided where utility lines cross building lines to prevent water from traveling in the trench backfill and entering beneath the structures.

GENERAL CONSTRUCTION PROCEDURES AND RECOMMENDATIONS Variations in subsurface conditions could be encountered during construction. To permit correlation between test boring data and actual subsurface conditions encountered during construction, it is recommended a registered Professional Engineering firm be retained to observe construction procedures and materials. Some construction problems, particularly degree or magnitude, cannot be reasonably anticipated until the course of construction. The recommendations offered in the following paragraphs are intended not to limit or preclude other conceivable solutions, but rather to provide our observations based on our experience and understanding of the project characteristics and subsurface conditions encountered in the borings.

7.1 Site Preparation and Grading Some concrete, brick and asphalt debris were encountered in some of the samples of fill material retrieved from the borings. Fill materials can contain organics, boulders, rubble, and other debris which could be encountered during site grading and general excavation. The earthwork and excavation contracts should contain provision for removal of unsuitable materials in the existing fill. Test pit excavations performed prior to construction can be used to evaluate the depth, extent and composition of uncontrolled fill at this site. ALPHA would be pleased to provide this service if desired. All areas supporting slab foundations, pools and pool decks, flatwork, pavement and areas to receive new fill should be properly prepared.

After completion of the necessary stripping, clearing, and excavating, and prior to placing any required fill, the exposed soil subgrade should be carefully evaluated by probing and testing. Any undesirable material (organic material, wet, soft, or loose soil) still in place should be removed.


17

The exposed soil subgrade should be further evaluated by proof-rolling with a heavy pneumatic tired roller, loaded dump truck or similar equipment weighing approximately 20 tons to check for pockets of soft or loose material hidden beneath a thin crust of possibly better soil. Proof-rolling procedures should be observed routinely by a Professional Engineer or his designated representative. Any undesirable material (organic material, wet, soft, or loose soil) exposed from the proof roll should be removed and replaced with well-compacted material as outlined in Section 7.3. Prior to placement of any fill, the exposed soil subgrade should then be scarified to a minimum depth of 6 inches and recompacted as outlined in Section 7.3.

If fill is to be placed on existing slopes (natural or constructed) steeper than six horizontal to one vertical (6:1), the fill materials should be benched into the existing slopes in such a manner as to provide a minimum bench width of five (5) feet. This should provide a good contact between the existing soils and new fill materials, reduce potential sliding planes and allow relatively horizontal lift placements. Even if fill is properly compacted as recommended in Section 7.3 of this report, fills in excess of about 10 ft to 12 ft are still subject to settlements over time of up to about 1 to 2 percent of the total fill thickness. This should be considered when designing utility lines under pavement or when backfilling uncontrolled fill excavations. Slope stability analysis of embankments (natural or constructed) and global stability analysis for retaining walls was not within the scope of this study. The contractor is responsible for designing any excavation slopes, temporary sheeting or shoring. Design of these structures should include any imposed surface surcharges. Construction site safety is the sole responsibility of the contractor, who shall also be solely responsible for the means, methods and sequencing of construction operations. The contractor should also be aware that slope height, slope inclination or excavation depths (including utility trench excavations) should in no case exceed those specified in local, state and/or federal safety regulations, such as OSHA Health and Safety Standard for Excavations, 29 CFR Part 1926, or successor regulations. Stockpiles should be placed well away from the edge of the excavation and their heights should be controlled so they do not surcharge the sides of the excavation. Surface drainage should be carefully controlled to prevent flow of water over the slopes and/or into the excavations. Construction slopes should be closely observed for signs of mass movement, including tension cracks near the crest or bulging at the toe. If potential stability problems are observed, a geotechnical engineer should be contacted immediately. Shoring, bracing or underpinning required for the project (if any) should be designed by a professional engineer registered in the State of Texas.

Due to the nature of the clay soils found near the surface at some of the borings, traffic of heavy equipment (including heavy compaction equipment) may create pumping and general deterioration of shallow soils. Therefore, some construction difficulties should be anticipated during periods when these soils are saturated.


18

7.2 Foundation Excavations All foundation excavations should be monitored to verify foundations bear on suitable material. The bearing stratum exposed in the base of all foundation excavations should be protected against any detrimental change in conditions. Surface runoff water should be drained away from excavations and not allowed to collect. All concrete for foundations should be placed as soon as practical after the excavation is made. Drilled piers should be excavated and concrete placed the same day. Prolonged exposure of the bearing surface to air or water will result in changes in strength and compressibility of the bearing stratum. Therefore, if delays occur, straight-shaft pier excavations should be slightly enlarged and deepened, or a new design penetration should be provided, in order to provide a fresh bearing surface. Underreamed pier excavations and grade beams for slab foundations should be slightly deepened and cleaned to provide a fresh bearing surface. All pier shafts should be at least 1.5 ft in diameter to facilitate clean-out of the base and proper monitoring. Concrete placed in pier holes should be directed through a tremie, hopper, or equivalent. Placement of concrete should be vertical through the center of the shaft without hitting the sides of the pier or reinforcement to reduce the possibility of segregation of aggregates. Concrete placed in piers should have a minimum slump of 5 inches (but not greater than 7 inches) to avoid potential honey-combing. Observations during pier drilling should include, but not necessarily be limited to, the following items:

Verification of proper bearing strata and consistency of subsurface stratification with regard to boring logs,

Confirmation the minimum required penetration into the bearing strata is achieved,

Complete removal of cuttings from bottom of pier holes,

Proper handling of any observed water seepage and sloughing of subsurface materials, No more than 2 inches of standing water should be permitted in the bottom of pier holes prior to placing concrete, and Verification of pier diameter, underream diameter and steel reinforcement.

Groundwater was encountered in Borings 2, 7 and 11 at depths of about 4 ft, 8 ft and 3 ft, respectively, below the ground surface. It is possible groundwater seepage could be encountered during pier installation. The risk of encountering groundwater during pier drilling is increased during or after periods of precipitation. Where submersible pumps or bailing cannot control groundwater, temporary casing may be required to control


19

seepage. For straight-sided drilled shafts, the casing should be properly seated into the limestone, and all groundwater and soil should be removed prior to beginning the design penetration. As casing is extracted, care should be taken to maintain a positive head of plastic concrete and minimize the potential for intrusion of water seepage. A separate bid item should be provided for casing on the contractor bid schedule. Some field adjustments in the depth of underreamed piers may be required in some areas to maintain the bottom of the piers above groundwater seepage. Adjustments in the depths of the piers should be observed in the field by ALPHA personnel. Also, the clay soils encountered at the boring locations are prone to collapse during construction of the underreamed portion of the pier foundation. Immediate placement of concrete after constructing the underream and/or the use of submersible pumps may be adequate to control underream collapse and/or seepage. Also, the existing fill materials could contain boulders or debris which could cause obstruction to piers drilling. Rock teeth and/or core barrels may be required to penetrate this rock and/or obstructions. The drilled shaft contract should contain provision for penetration or removal of rock and obstructions. 7.3 Fill Compaction Materials used as select, non-expansive material should have a liquid limit less than 35, a plasticity index (PI) not less than about 4 nor greater than 15 and contain no more than 0.5 percent fibrous organic materials, by weight. All select material should contain no deleterious material and should be compacted to a dry density of at least 95 percent standard Proctor maximum dry density (ASTM D 698) and within the range of 1 percentage point below to 3 percentage points above the material's optimum moisture content. The plasticity index and liquid limit of material used as select non-expansive material should be routinely verified during placement using laboratory tests. Visual observation and classification should not be relied upon to confirm the material to be used as select, non-expansive material satisfies the above Atterberg-limit criteria. Flexible base used as non-expansive fill in the building pad should consist of material meeting the requirements of TxDOT Standard Specifications Item 247, Type A, B, C, or D, Grade 1, 2 or 3. The flexible base should be compacted to at least 95 percent of standard Proctor maximum dry density (ASTM D 698) and within the range of 2 percentage points below to 2 percentage points above the material's optimum moisture content. The recommendations below pertain to fill placement for general site grading. Any fill placed as moisture conditioned soils should conform to the recommendations in Section 6.2. Clay, gravelly clay, sandy clay and shaly clay soils with a plasticity index equal to or greater than 25 should be compacted to a dry density between 93 and 98 percent of standard Proctor maximum dry density (ASTM D 698). The compacted moisture content of the clays during placement should be within the range of 2 to 6 percentage points above optimum.


20

Clay, gravelly clay and clayey sand soils with a plasticity index below 25 should be compacted to a dry density of at least 95 percent of standard Proctor maximum dry density (ASTM D 698) and within the range of 1 percentage point below to 3 percentage points above the material's optimum moisture content. Clayey materials used as fill should be processed and the largest particle or clod should be less than 6 inches prior to compaction. In cases where either mass fills or utility lines are more than 10 ft deep, the fill/backfill below 10 ft should be compacted to at least 98 percent of standard Proctor maximum dry density (ASTM D-698) and within 2 percentage points of the material's optimum moisture content. The portion of the fill/backfill shallower than 10 ft should be compacted as outlined above. Compaction should be accomplished by placing fill in about 8-inch thick loose lifts and compacting each lift to at least the specified minimum dry density. Field density and moisture content tests should be performed on each lift. 7.4 Groundwater Groundwater was encountered at depths of about 3 ft to 8 ft below the ground surface in Borings 2, 7 and 11. Shallower groundwater seepage could be encountered in excavations for foundations, utilities and other general excavations at this site. The risk of seepage increases with depth of excavation and during or after periods of precipitation. Standard sump pits and pumping may be adequate to control seepage on a local basis. In any areas where cuts are made to establish final grades, attention should be given to possible seasonal water seepage that could occur through natural cracks and fissures in the newly exposed stratigraphy. In these areas, subsurface drains may be required to intercept seasonal groundwater seepage. The need for these or other de-watering devices should be carefully addressed during construction. Our office could be contacted to visually observe the final pads to evaluate the need for such drains.


21

LIMITATIONS Professional services provided in this geotechnical exploration were performed, findings obtained, and recommendations prepared in accordance with generally accepted geotechnical engineering principles and practices. The scope of services provided herein does not include an environmental assessment of the site or investigation for the presence or absence of hazardous materials in the soil, surface water or groundwater. ALPHA, upon written request, can be retained to provide same. ALPHA TESTING, INC. is not responsible for conclusions, opinions or recommendations made by others based on this data. Information contained in this report is intended for the exclusive use of the Client (and their designated design representatives), and is related solely to design of the specific structures outlined in Section 2.0. No party other than the Client (and their designated design representatives) shall use or rely upon this report in any manner whatsoever unless such party shall have obtained ALPHA’s written acceptance of such intended use. Any such third party using this report after obtaining ALPHA’s written acceptance shall be bound by the limitations and limitations of liability contained herein, including ALPHA’s liability being limited to the fee paid to it for this report. Recommendations presented in this report should not be used for design of any other structures except those specifically described in this report. In all areas of this report in which ALPHA may provide additional services if requested to do so in writing, it is presumed that such requests have not been made if not evidenced by a written document accepted by ALPHA. Further, subsurface conditions can change with passage of time. Recommendations contained herein are not considered applicable for an extended period of time after the completion date of this report. It is recommended our office be contacted for a review of the contents of this report for construction commencing more than one (1) year after completion of this report. Non-compliance with any of these requirements by the Client or anyone else shall release ALPHA from any liability resulting from the use of, or reliance upon, this report. Recommendations provided in this report are based on our understanding of information provided by the Client about characteristics of the project. If the Client notes any deviation from the facts about project characteristics, our office should be contacted immediately since this may materially alter the recommendations. Further, ALPHA TESTING, INC. is not responsible for damages resulting from workmanship of designers or contractors and it is recommended the Owner retain qualified personnel, such as a Geotechnical Engineering firm, to verify construction is performed in accordance with plans and specifications.

APPENDIX


A-1 METHODS OF FIELD EXPLORATION Using standard rotary drilling equipment, a total of twelve (12) test borings were performed for this geotechnical exploration at the approximate locations shown on the Boring Location Plan, Figure 1. The test boring locations were staked by either pacing or taping and estimating right angles from landmarks which could be identified in the field and as shown on the site plan provided during this study. The locations of the test borings shown on the Boring Location Plan are considered accurate only to the degree implied by the methods used to define them. Relatively undisturbed samples of the cohesive subsurface materials were obtained by hydraulically pressing 3-inch O.D. thin-wall sampling tubes into the underlying soils at selected depths (ASTM D 1587). These samples were removed from the sampling tubes in the field and examined visually. One representative portion of each sample was sealed in a plastic bag for use in future visual examinations and possible testing in the laboratory. Some soil samples were obtained using split-spoon sampling procedures in accordance with ASTM Standard D 1586. Disturbed samples were obtained at selected depths in the borings by driving a standard 2-inch O.D. split-spoon sampler 18 inches into the subsurface material using a 140-pound hammer falling 30 inches. The number of blows required to drive the split-spoon sampler the final 12 inches of penetration (N-value) is recorded in the appropriate column on the Log of Boring sheets. A modified version of the Texas Cone Penetration (TCP) test was completed in the field to determine the apparent in-place strength characteristics of the rock type materials. A 3-inch diameter steel cone driven by a 170-pound hammer dropped 24 inches is the basis for TxDOT strength correlations. In this case, ALPHA TESTING, INC. has modified the procedure by using a 140-pound hammer dropping 30-inches for completion of the field test. Depending on the resistance (strength) of the materials, either the number of blows of the hammer required to provide 12 inches of penetration, or the inches of penetration of the cone due to 100 blows of the hammer are recorded on the field log and are shown on the Log of Boring sheets as “TX Cone” (reference TxDOT Test Method TEX 132-E, as modified). Logs of the borings are included in the Appendix of this report. The logs show a visual description of subsurface strata encountered in the borings using the Unified Soil Classification System. Sampling information, pertinent field data, and field observations are also included. The subsurface samples will be retained in the laboratory for at least 14 days and then discarded unless the Client requests otherwise.

GEOTECHNICAL EXPLORATIONFORT WORTH SOUTH APARTMENTSBROADWAY AVENUE ANDSOUTH CALHOUN STREETFORT WORTH, TEXASALPHA PROJECT NO. W162304

BORING LOCATION PLAN

FIGURE 1

B-1

B-3

B-2

B-4 B-5

B-6 B-7

B-8

B-9

B-10

B-11

B-12

BROADWAY AVENUE

SO

UT

H C

AL

HO

UN

ST

RE

ET

N

APPROXIMATE BORING LOCATION


B-1 METHODS OF LABORATORY TESTING Representative samples were evaluated and classified by a qualified member of the Geotechnical Division and the boring logs were edited as necessary. To aid in classifying the subsurface materials and to determine the general engineering characteristics, natural moisture content tests (ASTM D 2216), Atterberg-limit tests (ASTM D 4318), percent material passing the No. 200 sieve tests (ASTM S 1140) and dry unit weight determinations were performed on selected samples. In addition, unconfined compressive strength tests (ASTM D 2166) and pocket-penetrometer tests were conducted on selected soil samples to evaluate the soil shear strength. Results of all laboratory tests described above are provided on the accompanying Log of Boring sheets. In addition to the Atterberg-limit tests, the expansive properties of the clay soils encountered were further analyzed by absorption swell tests. The swell test is performed by placing a selected sample in a consolidation machine and applying either the approximate current or expected overburden pressure and then allowing the sample to absorb water. When the sample exhibits very little tendency for further expansion, the height increase is recorded and the percent free swell and total moisture gain calculated. Results of the absorption swell test are provided on the Swell Test Data sheet, Figure 2 included in this appendix.

Boring No.

Sample Depth

Vertical Pressure,

psfLiquid Limit

Plastic Limit

Plasticity Index

Initial Moisture

Final Moisture

Free Swell

1 5 625 72 24 48 21% 23% 0.3%

3 3 375 65 24 41 15% 26% 0.9%

8 7 875 48 21 27 14% 20% 2.5%

SWELL TEST DATA

FIGURE 2 SWELL DATA SHEET


FORT WORTH SOUTH APARTMENTS

BROADWAY AVENUE AND

FORT WORTH, TEXASALPHA REPORT NO. W162304

SOUTH CALHOUN STREET

Brown GRAVELLY CLAY - FILL

Brown CLAY

Reddish Brown CLAY

Reddish Brown SHALY CLAY

Gray SHALY CLAY

TEST BORING TERMINATED AT 20 FT

2.0

6.0

8.0

17.0

20.0

4.5+

4.5+

4.0

3.5

4.5+

4.5+

4.5+

12

20

21

24

25

23

14

72

60

24

22

48

38

MATERIAL DESCRIPTION

West:

LOG OF BORING NO.: 15058 Brush Creek Rd.Fort Worth, Texas76119Phone: 817-496-5600Fax: 817-496-5608www.alphatesting.com

Start Date: 9/22/2016 End Date: 9/22/2016

Project: Fort Worth South Apartments

Client: StoneHawk Capital Partners, LLC

Hammer Drop (lbs / in):

Surface Elevation:

Uni

t Dry

Wei

ght

(pcf

)

Dep

th, f

eet

5

10

15

20

25

30

35

GROUND WATER OBSERVATIONS

Sheet 1 of 1

After Hours (ft): Poc

ket

Pen

etro

met

er (

tsf)

On Rods (ft):

Drilling Method: CONTINUOUS FLIGHT AUGER

Unc

onfin

ed C

omp.

Str

engt

h (t

sf)

. NONE

After Drilling (ft):. DRY

.

PROJECT NO.: W162304

Location: Fort Worth, Texas

Wat

er C

onte

nt, %

% P

assi

ngN

o. 2

00 S

ieve

Liqu

id L

imit

Pla

stic

Lim

it

Pla

stic

ity In

dex

Gra

phic

Log

North:

TX

Con

e or

Std

.P

en. (

blow

s/ft,

in)

Rec

over

y %

RQ

D

Sam

ple

Typ

e

4" CONCRETEBrown GRAVELLY CLAY - FILL

Dark Brown CLAY

Brown and Tan CLAY with calcareous nodules


Gray LIMESTONE with shale seams


0.3

2.0

8.0

10.0

22.0

35.0

106

1.25

3.0

3.0

2.25

4.0

4.5+ 4.6

13

34

31

25

22

8

22

70 24 46

100/1.75"

100/0.5"

100/1"

100/1.25"


West:





Hammer Drop (lbs / in): 140 / 30

Surface Elevation:

Uni

t Dry

Wei

ght

(pcf

)

Dep

th, f

eet

5

10

15

20

25

30

35


Sheet 1 of 1


ket

Pen

etro

met

er (

tsf)

On Rods (ft): 4


Unc

onfin

ed C

omp.

Str

engt

h (t

sf)

.


.



Wat

er C

onte

nt, %

% P

assi

ngN

o. 2

00 S

ieve

Liqu

id L

imit

Pla

stic

Lim

it

Pla

stic

ity In

dex

Gra

phic

Log

North:

TX

Con

e or

Std

.P

en. (

blow

s/ft,

in)

Rec

over

y %

RQ

D

Sam

ple

Typ

e

Dark Gray CLAY with limestone fragments - FILL

Brown CLAY with calcareous nodules

Tan and Brown CLAY with calcareous nodules


Grayish Brown SHALY CLAY


2.0

6.0

8.0

18.0

20.0

4.5+

4.5+

4.5+

4.5+

3.5

4.5+

4.0

10

15

13

14

25

23

23

65 24 41


West:






Surface Elevation:

Uni

t Dry

Wei

ght

(pcf

)

Dep

th, f

eet

5

10

15

20

25

30

35


Sheet 1 of 1


ket

Pen

etro

met

er (

tsf)

On Rods (ft):


Unc

onfin

ed C

omp.

Str

engt

h (t

sf)

. NONE


.



Wat

er C

onte

nt, %

% P

assi

ngN

o. 2

00 S

ieve

Liqu

id L

imit

Pla

stic

Lim

it

Pla

stic

ity In

dex

Gra

phic

Log

North:

TX

Con

e or

Std

.P

en. (

blow

s/ft,

in)

Rec

over

y %

RQ

D

Sam

ple

Typ

e

Brown GRAVELLY CLAY with limestone fragmentsand construction debris - FILL

Dark Brown CLAY

Reddish Brown CLAY with calcareous nodules

Tan and Brown CLAY


Gray CLAY SHALE with limestone seams and layers


2.0

6.0

8.0

12.0

20.0

30.0

105

4.5+

4.0

4.0

4.0

4.5+

3.9

9

22

25

24

23

22

24

17

16

58 20 38

100/12"

100/8"

100/2.75"


West:






Surface Elevation:

Uni

t Dry

Wei

ght

(pcf

)

Dep

th, f

eet

5

10

15

20

25

30

35


Sheet 1 of 1


ket

Pen

etro

met

er (

tsf)

On Rods (ft):


Unc

onfin

ed C

omp.

Str

engt

h (t

sf)

. NONE


.



Wat

er C

onte

nt, %

% P

assi

ngN

o. 2

00 S

ieve

Liqu

id L

imit

Pla

stic

Lim

it

Pla

stic

ity In

dex

Gra

phic

Log

North:

TX

Con

e or

Std

.P

en. (

blow

s/ft,

in)

Rec

over

y %

RQ

D

Sam

ple

Typ

e

2" ASPHALTDark Brown GRAVELLY CLAY - FILL

Dark Brown CLAY





0.3

4.0

8.0

12.0

22.0

30.0

108

3.5

3.5

3.5

4.5+

4.5+ 4.6

6

26

32

27

25

21

19

67 25 42

100/2"

100/0.5"

100/1.25"


West:






Surface Elevation:

Uni

t Dry

Wei

ght

(pcf

)

Dep

th, f

eet

5

10

15

20

25

30

35


Sheet 1 of 1


ket

Pen

etro

met

er (

tsf)

On Rods (ft):


Unc

onfin

ed C

omp.

Str

engt

h (t

sf)

. NONE


.



Wat

er C

onte

nt, %

% P

assi

ngN

o. 2

00 S

ieve

Liqu

id L

imit

Pla

stic

Lim

it

Pla

stic

ity In

dex

Gra

phic

Log

North:

TX

Con

e or

Std

.P

en. (

blow

s/ft,

in)

Rec

over

y %

RQ

D

Sam

ple

Typ

e


Tan CLAY with calcareous nodules - possible fill

Brown GRAVELLY CLAY - possible fill



4.0

6.0

12.0

20.0

4.5+

4.5+

4.5+

4.5+

4.5+

4.0

4.5+

12

13

12

11

10

30

23

52

47 21 26


West:






Surface Elevation:

Uni

t Dry

Wei

ght

(pcf

)

Dep

th, f

eet

5

10

15

20

25

30

35


Sheet 1 of 1


ket

Pen

etro

met

er (

tsf)

On Rods (ft):


Unc

onfin

ed C

omp.

Str

engt

h (t

sf)

. NONE


.



Wat

er C

onte

nt, %

% P

assi

ngN

o. 2

00 S

ieve

Liqu

id L

imit

Pla

stic

Lim

it

Pla

stic

ity In

dex

Gra

phic

Log

North:

TX

Con

e or

Std

.P

en. (

blow

s/ft,

in)

Rec

over

y %

RQ

D

Sam

ple

Typ

e

Brown and Orangish SANDY CLAY - FILL


Brown CLAYEY SAND - FILL

Dark Gray CLAY


Tan LIMESTONE with clay seams and layers



2.0

6.0

8.0

12.0

20.0

22.0

35.0

105

4.5+

4.5+

4.5+

1.25

4.5+

2.6

8

16

14

33

28

20

23

64 23 41

100/1.5"

100/1.5"

100/1"

100/0.5"


West:






Surface Elevation:

Uni

t Dry

Wei

ght

(pcf

)

Dep

th, f

eet

5

10

15

20

25

30

35


Sheet 1 of 1


ket

Pen

etro

met

er (

tsf)

On Rods (ft): 8


Unc

onfin

ed C

omp.

Str

engt

h (t

sf)

.


.



Wat

er C

onte

nt, %

% P

assi

ngN

o. 2

00 S

ieve

Liqu

id L

imit

Pla

stic

Lim

it

Pla

stic

ity In

dex

Gra

phic

Log

North:

TX

Con

e or

Std

.P

en. (

blow

s/ft,

in)

Rec

over

y %

RQ

D

Sam

ple

Typ

e

Brown CLAY - FILL

Dark Brown CLAY - possible fill



Tan CLAY with limestone fragments



2.0

4.0

6.0

8.0

12.0

20.0

4.5+

4.5+

4.5+

4.5+

4.5+

4.5+

4.5+

16

16

14

13

11

21

23

48 21 27


West:






Surface Elevation:

Uni

t Dry

Wei

ght

(pcf

)

Dep

th, f

eet

5

10

15

20

25

30

35


Sheet 1 of 1


ket

Pen

etro

met

er (

tsf)

On Rods (ft):


Unc

onfin

ed C

omp.

Str

engt

h (t

sf)

. NONE


.



Wat

er C

onte

nt, %

% P

assi

ngN

o. 2

00 S

ieve

Liqu

id L

imit

Pla

stic

Lim

it

Pla

stic

ity In

dex

Gra

phic

Log

North:

TX

Con

e or

Std

.P

en. (

blow

s/ft,

in)

Rec

over

y %

RQ

D

Sam

ple

Typ

e

2" ASPHALTBrown GRAVELLY CLAY - FILL

Brown CLAY


Tan CLAY with calacareous nodules

Tan CLAY


TEST BORING TERMIANTED AT 20 FT

0.2

4.0

6.0

8.0

13.0

15.0

20.0

4.5+

4.5+

4.5+

4.5+

4.5+

19

16

14

12

10

20

48 23 25

8

100/1.25"

100/1.25"


West:






Surface Elevation:

Uni

t Dry

Wei

ght

(pcf

)

Dep

th, f

eet

5

10

15

20

25

30

35


Sheet 1 of 1


ket

Pen

etro

met

er (

tsf)

On Rods (ft):


Unc

onfin

ed C

omp.

Str

engt

h (t

sf)

. NONE


.



Wat

er C

onte

nt, %

% P

assi

ngN

o. 2

00 S

ieve

Liqu

id L

imit

Pla

stic

Lim

it

Pla

stic

ity In

dex

Gra

phic

Log

North:

TX

Con

e or

Std

.P

en. (

blow

s/ft,

in)

Rec

over

y %

RQ

D

Sam

ple

Typ

e

Brown GRAVELLY CLAY with asphalt fragments -FILL

Brown CLAY

Tan and Brown CLAY

Tan CLAY


Tan LIMESTONE with clay seams and layers


4.0

6.0

8.0

12.0

17.0

20.0

4.0

4.25

4.5+

6

7

27

22

21

23

57 22 35

32

8

100/0.5"

100/1.25"


West:






Surface Elevation:

Uni

t Dry

Wei

ght

(pcf

)

Dep

th, f

eet

5

10

15

20

25

30

35


Sheet 1 of 1


ket

Pen

etro

met

er (

tsf)

On Rods (ft):


Unc

onfin

ed C

omp.

Str

engt

h (t

sf)

. NONE


.



Wat

er C

onte

nt, %

% P

assi

ngN

o. 2

00 S

ieve

Liqu

id L

imit

Pla

stic

Lim

it

Pla

stic

ity In

dex

Gra

phic

Log

North:

TX

Con

e or

Std

.P

en. (

blow

s/ft,

in)

Rec

over

y %

RQ

D

Sam

ple

Typ

e

Brown GRAVELLY CLAY with concrete debris andbrick - FILL

Brown SANDY CLAY - possible fill

Brown, Tan, and Gray SHALY CLAY


Gray CLAY SHALE with limestone seams and layers

Gray SHALE


4.0

6.0

8.0

12.0

17.0

20.0

3.75

4.5

5

11

33

22

23

57 22 35

7

7

100/1.25"

92/10"

100/0.75"


West:






Surface Elevation:

Uni

t Dry

Wei

ght

(pcf

)

Dep

th, f

eet

5

10

15

20

25

30

35


Sheet 1 of 1


ket

Pen

etro

met

er (

tsf)

On Rods (ft): 3


Unc

onfin

ed C

omp.

Str

engt

h (t

sf)

.


.



Wat

er C

onte

nt, %

% P

assi

ngN

o. 2

00 S

ieve

Liqu

id L

imit

Pla

stic

Lim

it

Pla

stic

ity In

dex

Gra

phic

Log

North:

TX

Con

e or

Std

.P

en. (

blow

s/ft,

in)

Rec

over

y %

RQ

D

Sam

ple

Typ

e

Brown GRAVELLY CLAY with concrete and asphaltdebris - FILL


Gray SHALY CLAY


11.0

18.0

20.0

4.5+

4.5+

4.5+

4.5+

9

9

12

17

11

25

17

71 49

66

19

24

30

42


West:






Surface Elevation:

Uni

t Dry

Wei

ght

(pcf

)

Dep

th, f

eet

5

10

15

20

25

30

35


Sheet 1 of 1


ket

Pen

etro

met

er (

tsf)

On Rods (ft):


Unc

onfin

ed C

omp.

Str

engt

h (t

sf)

. NONE


.



Wat

er C

onte

nt, %

% P

assi

ngN

o. 2

00 S

ieve

Liqu

id L

imit

Pla

stic

Lim

it

Pla

stic

ity In

dex

Gra

phic

Log

North:

TX

Con

e or

Std

.P

en. (

blow

s/ft,

in)

Rec

over

y %

RQ

D

Sam

ple

Typ

e

TEXAS CONE PENETRATION

FILL

LIMESTONE

(MH), Elastic SILT

SANDSTONE

(GP), Poorly Graded GRAVEL

LOWMEDIUMHIGHVERY HIGH

4 TO 1516 TO 2526 TO 35OVER 35

SAMPLING SYMBOLS

(OL), ORGANIC SILT

(OH), ORGANIC CLAY

8.0" OR LARGER3.0" TO 8.0"

0.75" TO 3.0"5.0 mm TO 3.0"

2.0 mm TO 5.0 mm0.4 mm TO 5.0 mm

0.07 mm TO 0.4 mm0.002 mm TO 0.07 mmLESS THAN 0.002 mm

SOIL & ROCK SYMBOLS

KEY TO SOIL SYMBOLSAND CLASSIFICATIONS

(CH), High Plasticity CLAY VERY LOOSELOOSEMEDIUMDENSEVERY DENSE

RELATIVE DENSITY OF COHESIONLESS SOILS (blows/ft)

0 TO 45 TO 1011 TO 3031 TO 50OVER 50

SHELBY TUBE (3" OD except wherenoted otherwise)

SPLIT SPOON (2" OD except wherenoted otherwise)

AUGER SAMPLE

ROCK CORE (2" ID except wherenoted otherwise)

PARTICLE SIZE IDENTIFICATION (DIAMETER)

(CL), Low Plasticity CLAY

(SP), Poorly Graded SAND

(GW), Well Graded GRAVEL

(GC), CLAYEY GRAVEL

(GM), SILTY GRAVEL

BOULDERSCOBBLESCOARSE GRAVELFINE GRAVELCOURSE SANDMEDIUM SANDFINE SANDSILTCLAY

TRACELITTLESOMEAND

1 TO 1011 TO 2021 TO 3536 TO 50

RELATIVE PROPORTIONS (%)

VERY SOFTSOFTFIRMSTIFFVERY STIFFHARD

LESS THAN 0.250.25 TO 0.500.50 TO 1.001.00 TO 2.002.00 TO 4.00OVER 4.00

SHEAR STRENGTH OF COHESIVE SOILS (tsf)

RELATIVE DEGREE OF PLASTICITY (PI)SHALE / MARL

(SC), CLAYEY SAND

(SW), Well Graded SAND

(SM), SILTY SAND

(ML), SILT

D A L L A S

2209 Wisconsin Street #100

Dallas, Texas 75229

T: 972.620.8911

F: 972.620.1302

F O R T W O R T H

5058 Brush Creek Road

Fort Worth, Texas 76119

T: 817.496.5600

F: 817.496.5608

H O U S T O N

6513 W. Little York Road

Houston, Texas 77040

T: 713.360.0460

F: 713.360.0481

S A N A N T O N I O

12766 O’Connor Road

San Antonio, Texas 78233

T: 210.249.2100

F: 210.249.2101

www.alphatesting.com

Geotechnical Construction Materials Environmental

TBPE NO. 813

http://www.alphatesting.com/

geotechnical exploration on fort worth …...2016/01/11 · geotechnical construction materials...

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