TERRA ENGINEERING, INC.

ReportGEOTECHNICAL INVESTIGATION

PROPOSED RESIDENCE7900 CORA STREET

LOTS 3, 4, & 5, BLOCK 18, HIGHLAND ADDITION(HCAD 0162610180003)

HOUSTON, TEXAS 77088

All-Terra Project No.: AE19-803-08

PREPARED FOR:

City of HoustonHousing & Community Development

Procurement Services601 Sawyer, 4th Floor

Houston, Texas 77007

PREPARED BY:

All-Terra Engineering, Inc.6200 Rothway, Suite 140Houston, Texas 77041(713) 574-2371 (office)(713) 574-2372 (fax)

April 1, 2019

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6200 Rothway, Suite 140, Houston, TX 77041 Tel: 713-574-2371 Fax: 713-574-2372

All-Terra Engineering, Inc.Geotechnical Engineering * Construction Materials Testing

April 1, 2019

Ms. Yvonne CantuCity of HoustonHousing & Community Development

Procurement Services601 Sawyer, 4th FloorHouston, Texas 77007

Re: ReportGeotechnical InvestigationProposed Residence

7900 Cora StreetLots 3, 4, & 5, Block 18, Highland Addition(HCAD 0162610180003)Houston, Texas 77088

Project No.: AE19-803-08

Dear Ms. Cantu:

All-Terra Engineering, Inc. is pleased to transmit our report of the geotechnicalinvestigation for the above-referenced project. The report provides data, analyses results, and recommendations that may be used for the design and construction of the proposed new residence.

We appreciate the opportunity to perform this geotechnical investigation and look forward to continued participation during the design and construction phases of this project. If you have any questions pertaining to this report or if we may be of further service, please contact me at your convenience.

Respectfully submitted,All-Terra Engineering, Inc. (F-9770)

_______________________________ ______________________________Bonifacio F. Musngi, Jr., P.E. Amanuel T. WudnehSenior Geotechnical Engineer Project Manager

File: c://2019/AE19-803-08_report.docx0044--0011--22001199

Project No. AE19-803-08April 1, 2019

TABLE OF CONTENTS

Page No.1.0 Introduction and Summary ................................................................................. 1

1.1 Introduction................................................................................................. 11.2 Summary of Findings.................................................................................. 2

1.2.1 Subsurface Soil Strata ..................................................................... 21.2.2 Groundwater Condition.................................................................... 31.2.3 Potential for Vertical Rise................................................................. 3

1.3 Summary of Recommendations ................................................................. 31.3.1 Recommended Site and Subgrade Preparation .............................. 31.3.2 Recommended Foundation System – PTI Slab-On-Grade................. 51.3.3 Recommended Foundation System – Drilled Underreamed Piers...... 71.3.4 Recommended Foundation System – Continuous Footings/Grade

Beams................................................................................................ 91.3.5 Recommended Foundation System – Shallow Spread Footings .......10

2.0 Field Investigation............................................................................................... 11 3.0 Laboratory Testing.............................................................................................. 12 4.0 Foundation Maintenance .................................................................................... 12 5.0 Construction Considerations ................................................................................... 14

6.0 Closing Remarks ................................................................................................ 14

APPENDIX

Plate No. 1 Vicinity MapPlate No. 2 Locations of BoringsPlate Nos. 3 and 4 Boring Logs (Boring Nos. B-1 and B-2)Plate No. 5 Key to Symbols Used in Boring Logs

Project No. AE19-803-08April 1, 2019 Page: 1

REPORTGEOTECHNICAL INVESTIGATION

PROPOSED RESIDENCE7900 CORA STREET

LOTS 3, 4, & 5, BLOCK 18, HIGHLAND ADDITION(HCAD 0162610180003)

HOUSTON, TEXAS 77088

1.0 INTRODUCTION AND SUMMARY

1.1 IntroductionThis report presents the results of the geotechnical investigation that may be used to support the design and construction of a proposed residence that will be constructed at 7900 Cora Street (Lots 3, 4, & 5 in Block 18 at Highland Addition, HCAD 0162610180003)in Houston, Texas. The area for the proposed residential development project is relatively flat that has presence of vegetation consisting of scattered trees, underbrush, and grasses. The site location for the proposed residence is shown on Plate No. 1.

The objectives of this geotechnical investigation were to define the subsurface soils and groundwater conditions at the site of the proposed residential development project and provide geotechnical design data, parameters, and recommendations for foundations thatmay be used to support the loads from the proposed residential structure.

This geotechnical investigation was performed by All-Terra Engineering, Inc. for the City of Houston Housing & Community Development Procurement Services through an email request and authorization on January 3, 2019.

The purposes of this geotechnical investigation were to:

• define the subsurface soil and groundwater conditions at the area of the proposed residence, and

• provide data, parameters, and recommendations that will support the design and construction of the proposed residential project.

The scope of work for this geotechnical investigation consisted of the following activities:

• Drill and sample 2 geotechnical borings to depths of 15 feet and 20 feet beneath the existing ground surface at the locations as shown on Plate No. 2.

• Obtain both disturbed and relatively undisturbed soil samples from the borings with continuous samples being taken from the ground surface to a depth of 10 feet and at 5-foot intervals thereafter.

• Measure groundwater levels in the borings during drilling and after the completion of drilling.

Project No. AE19-803-08 April 1, 2019 Page: 2

• Backfill the borings with soil cuttings after the completion of the drilling activities.

• Perform geotechnical laboratory tests on soil samples recovered during drilling in order to determine the engineering properties of the site soils. Laboratory testing included Atterberg limits tests, moisture content tests, percent soil finer than the No. 200 sievetests, unconfined compression test, and density of soil test. Soil classification was performed in accordance with the guidelines of ASTM D 2487 and ASTM D 2488.

• Prepare boring logs based on the results of the laboratory tests and visual soil classifications.

• Characterize the site subsoil and groundwater conditions.

• Perform engineering analyses as necessary to provide foundation recommendations that may be used for the design of the proposed structure.

• Prepare and submit an electronic file of the report that presents the data, findings, and recommendations of the geotechnical investigation.

1.2 Summary of FindingsThe pertinent findings of this geotechnical investigation that pertain to the design and construction of the proposed residence are provided below.

1.2.1 Subsurface Soil StrataThe subsurface soil strata at the boring locations within the proposed residence are described by the laboratory test results and the boring logs for BoringNos. B-1 and B-2 as shown on Plate Nos. 3 and 4.

Data from the 2 geotechnical borings drilled suggest that the upper 20 feet ofthe overburden soils are generally composed of 3 separate layers as described below.

Layer Depth *(ft) Soil Description

I 0 – 13 Gray, light gray, and tan SANDY LEAN CLAY (CL), firm to very stiff.

II 13 – 17 Gray and reddish brown FAT CLAY (CH), very stiff.

III 17 - 20 Tan SILTY SAND (SM), encountered in Boring No. B-1 only.* Measured below the ground surface at the time of our field exploration activities.

Laboratory testing was performed on selected samples of the subsurface materials obtained to classify the soils in accordance with ASTM D 2487 and to define the engineering properties of the soils. Portions of the test results


indicating the high and low values of specific testing are provided in the table below:

LAYER DEPTH(FT)

LIQUIDLIMIT (%)

PLASTICITYINDEX

(%)

MOISTURECONTENT

(%)

PASSING NO. 200 SIEVE

(%)

COMPR. STRENGTH

(TSF)

HIGH LOW HIGH LOW HIGH LOW HIGH LOW HIGH LOW

I 0 – 13 35 29 20 15 17.9 15.5 67.1 60.4 --

II 13 – 17 -- -- 21.2 17.4 -- --

III 17 – 20 -- -- 17.1 -- --

-- No sample was tested

1.2.2 Groundwater ConditionGroundwater was encountered at depths of 13.0 and 12.0 feet beneath the surface during the drilling of Boring Nos. B-1 and B-2, respectively, and was measured at depths of 8.5 and 9.0 feet in Boring Nos. B-1 and B-2, respectively, after the completion of drilling. The bore holes were backfilled with soil cuttings after the completion of drilling.

It is possible that seasonal variations will cause fluctuations in the water leveldata obtained at the time of our field investigation. Long term monitoring of the groundwater level data within the proposed development is beyond the scope of our study. It should be noted that recommendations contained in this report are based on groundwater depths at the time of this geotechnical investigation and that an accurate determination of the true groundwater levelsmay require several days or even months of observations.

1.2.3 Potential for Vertical RiseThe upper clayey soils within the project area exhibited medium plasticitywith moderate potential for vertical movement (shrink/swell). The maximum potential vertical rise (PVR) of the upper 8 feet of the site soils, based on worst case soil moisture condition, is less than ½ inch under a 144 psf [1pound per square inch (psi)] restraining load. The potential vertical riseanalyses were performed by using the Texas Department of Transportation (TxDOT) Test Method Tex-124-E and the results of laboratory index tests.

1.3 Summary of RecommendationsThe recommendations, as summarized below, are provided for use in the design and construction of the proposed residence.

1.3.1 Recommended Site and Subgrade PreparationTo provide adequate foundation support to the proposed residential building, it is vital that the proposed building area be properly prepared. The contractorshould establish and maintain positive site drainage throughout the


construction period because surface soils are sensitive to moisture. Wet soil conditions during and following rainy weather will adversely affect constructionactivities. If the surface soils become overly saturated and unable to support construction activity, or rut and pump under equipment traffic, construction should not proceed until the surface conditions have improved or have been remediated. Remediation typically involves disking, drying, and recompaction during dry weather; excavation and replacement; or treatment with a chemical additive. Chemical treatment (stabilization) of the building pad subgrade before fill placement is effective in creating a firm/stable subgrade on which construction may proceed if construction commences during or after a wet period. It is then recommended that site and subgrade preparation include the following activities.

• Establish positive site drainage and install storm water drainage structures, as needed.

• Strip any vegetation and organic topsoil to a depth of at least 6 inches and as necessary to achieve the desired grade, as applicable.

• Proofroll the exposed subgrade soils with a rubber-tired vehicle weighing about 20 tons such as a dump truck, a maintainer, a pneumatic equipment, or other equivalent suitable equipment as approved by the engineer, observing the soils during proofrolling so as to detect any wet, soft, loose, or unstable/pumping soils and treating such soils with suitable drying orstabilizing agents or removing the unsuitable soils and replacing with properly compacted select fill. A compactor or bulldozer, or similar tracked equipment/vehicle is not acceptable for proofrolling activities. Proofrolling should extend at least 5 feet beyond the building limitsdepending on the type of foundation system used. The geotechnical engineer or an experienced soil technician should observe proofrolling operations to delineate areas that require remediation, if any. The proofrolling activities should be properly documented to ensure that the building area had been properly prepared prior to the placement of the building pad fill soils.

• Compact the exposed subgrade soils to an in-place dry density equal toat least 95% of the maximum standard dry density (ASTM D 698) at a moisture content within 2% of the optimum moisture content.

• Place properly compacted select fill (thickness depending on the type of foundation being considered) as necessary to achieve the desired grade elevation.

Select fill should consist of inactive lean clays (classified as CL soils) with a maximum liquid limit of 35, a plasticity index range of 10 to 20, and at least 50% passing the No. 200 sieve. The select fill should be placed in 8-inch thick loose lifts (6-inch compacted lifts) and compacted to an in-place dry


density equal to at least 95% of the maximum standard dry density (ASTM D698) at a moisture content within 2% of the optimum moisture content.Testing of each 6-inch thick lift of select fill should be at a frequency of one in-place density and moisture content test for each 2,000 square feet or less with a minimum of three tests per lift.

Depending upon weather conditions, difficulty may be encountered in adequately densifying/compacting the surficial site soils. If the surficial soils are unsuitably wet, excess pore pressures (“pumping”) may develop and excessive displacement of the subgrade soils may occur during site and subgrade preparation. If the site subgrade soils become unsuitably wet, theconstruction contractor should:

• bring the subgrade soils to within 2% of the optimum moisture content by discing/raking these materials, or

• dry the soils by blending a stabilizing agent (lime or fly ash) with the unsuitably wet soils, or

• remove the unsuitably wet soils and replace with properly compacted select fill having an acceptable moisture content.

Additional Considerations for Slab-on-Grade Floors:- A bentonite seal or plug of similar material may be placed within utility

trenches where the trenches exit the slab footprint. The seals should be located at least 3 feet outside of the building and should be at least 2-foot in length; bentonite should not be placed under grade beams. The bentonite seal will prevent infiltration of water into the utility bedding and backfill from water sources located outside of the building footprint.

- Vapor retarder not less than 10 mils thick should be placed under the concrete floor slab-on-grade to reduce the transmission of water vapor from the foundation soil through the concrete slab. For slabs exposed to ambient conditions of temperature and humidity, a vapor retarder also reduces the amount of water that will condense on the slab during periods of high relative humidity. Local practice is to place the concrete floor directly on the vapor retarder. The vapor retarder should function as a slip-sheet to reduce subgrade drag friction. The vapor retarder should be installed according to the guidelines of ASTM E 1643.

1.3.2 Recommended Foundation System – PTI Slab-On-GradeThe Post-Tensioning Institute (PTI) provides design standards for post-tensioned slab-on-grade. PTI parameters are selected based on the predominant soil type, the type of clay mineral, and percentage of clay. The appropriate Post Tensioning Institute (PTI) 3rd Edition with 2008 Supplement design criteria for slab-on-grade foundation systems are shown in the


following table. According to PTI 3rd Edition, edge moisture variation distance estimates (em) are calculated based on a climatic factor known as Thornthwaite Moisture Index (Im) as well as other properties including an unsaturated diffusion coefficient as a primary factor. The differential movement estimates (ym) for PTI 3rd Edition were calculated based on soil characteristics using the guidelines and methodologies by the PTI 3rd Book with 2008 Supplement. The actual soil movements are affected by soil moisture conditions that are also influenced by non-climatic factors such as vegetation, slope, drainage, irrigation, downspouts, and leaking water lines. Precautions should be taken to ensure that proper surface drainage is maintained during and after construction to keep uniform moisture in the foundation soils.

The loads of the proposed residential building may then be supported on a post-tensioned slab founded on at least 1.0 foot of properly compacted select fill soil prepared in accordance with Section 1.3.1 of this report. The select fill should be placed over the foundation area and to a distance of at least five (5) feet beyond the perimeters of the foundation. Provided below are the parameters for the design of post-tensioned slab-on-grade in accordance with the Post Tensioning Institute (PTI) requirements and guidelines as contained in the Third Edition of the PTI’s 2004 publication entitled “Design and Construction of Post-Tensioned Slabs-on-Ground”.

PTI Slab Design Parameters(PTI 3rd Edition)

Design Parameters Design Values

Predominant Soil Type Clay

Predominant Clay Mineral Montmorillonite

Percentage of Fine Clay(5μ / Pass 200 Sieve) 30%*

Thornthwaite Moisture Index (Im) +18

Depth to Constant Soil Suction 9.0 feet

Wet Suction Profile (pF) 2.9

Dry Suction Profile (pF) 4.5

Constant Soil Suction (pF) 3.45

Moisture Velocity (estimated) 0.70 inch/monthEdge Moisture Variation Distance (em)

Center Lift (Shrink)Edge Lift (Swell)

9.0 feet4.9 feet


Design Parameters Design ValuesDifferential Soil Movement (ym)

Center Lift (Shrink)Edge Lift (Swell)

0.49 inch0.28 inch

Effective Plasticity Index (PI) 19

Allowable Bearing Pressure** 1,200 psf* Estimated value** For grade beams that are founded at least 12 inches below finished grade.

The PTI methods for design of slab-on-grade foundations are essentially empirical design techniques and the parameters provided above are based on our interpretation of the soil boring, laboratory test results, and the criteria published in the PTI’s 3rd Edition with 2008 Supplement design manuals.

We recommend that the grade beams extend below final grade to a depth based on structural design and considerations. The grade beam width and depth should be properly evaluated by the structural engineer. Grade beams may be thickened and widened to serve as spread footings at concentrated load areas.

1.3.3 Recommended Foundation System – Drilled Undereamed PiersThe loads of the proposed residential building may also be supported on drilled underreamed piers. The underreamed drilled piers may be founded at a depth of at least 8.0 feet beneath the existing grade or at least 8.0 feetbeneath finished grade. The underreamed drilled piers (maximum pier bell diameter of 4 feet) should be designed for maximum net allowable bearing pressures of 3,400 psf for axial compression dead loads plus sustained live loads and 5,100 psf for axial compression dead loads plus sustained and transient live loads, whichever is greater in bell diameter.

The allowable shaft friction in compression and tension for the portions of the drilled pier shafts below a depth of 5 feet beneath finished grade is 250 psf.

The center-to-center spacing of the drilled piers should be equal to a minimum of 1.5 times the average drilled pier bell diameter of adjacent drilled piers. Should piers be located closer than 1.5 bell diameters, measured center-to-center, a reduction in the allowable net bearing pressures may be required. All-Terra should be notified for further evaluation in order to determine the appropriate reduction values.

Caving of pier bell excavations may occur during the construction of the drilled piers. The adverse effects of pier bell excavation caving can be limited by:


- the designer using a maximum bell-to-shaft diameter ratio of 3,

- the designer minimizing pier bell diameters, and

- the construction contractor minimizing the time between the completion of pier bell under-reaming and concrete placement.

If necessary, a trial pier may be constructed prior to construction to assure that the pier bell excavations will be free from seepage water and will remain open and free from debris due to sloughing and/or caving.

For cases where drilled pier excavations cave so rapidly that concrete cannot be placed quickly enough to allow construction of the piers, it will be necessary to use casing to maintain an open drilled pier excavation or consider the use of drilled straight shafts.

Use of the above recommended allowable net foundation bearing pressures provide for:

- a safety factor of at least 3.0 against a drilled pier bearing failure under axial compression dead loads plus sustained live loads,

- a safety factor of at least 2.0 against a drilled pier bearing failure under axial compression dead loads plus sustained and transient live loads, and

- a maximum total settlement of the drilled piers of less than 1 inch and a maximum differential settlement of the drilled piers of 0.5 inch, assuming a maximum pier bell diameter of 4 feet.

• Grade BeamsGrade beams should be at least 12 inches wide, extend at least 1.5 feet below finished grade, and be founded on drilled piers. Carton forms to create a void beneath the grade beams and the subgrade soils are not required. Grade beams may be formed directly on the properly prepared building pad soils.

• Slab-on-Grade FloorThe floor for the proposed residential building may consist of a slab-on-grade floor placed over at least 1.5 feet of properly compacted select fillprepared in accordance with site preparation as described in Section 1.3.1 of this report. To achieve the required finished grade, it may be necessary that the existing subgrade be over-excavated to a depth that will allow the placement of the recommended thickness of select fill soils.An allowable net bearing pressure of 600 psf can be used for slab-on-grade bearing on properly compacted select fill. It is suggested that cushion sand (leveling sand) not be placed within the area of the slab-on-grade floor. If cushion sand becomes wet, erosion and/or settling of the


sand may occur which can result in the formation of voids beneath the floor and associated structural distress. The select fill soils should be placed and extend about five (5) feet beyond the perimeters of the foundation.

• Structural FloorAs an alternative to the use of a slab-on-grade floor and placement of select fill soil, the floor for the proposed residential building may also consist of a floor placed over void boxes or an elevated floor system (structural floor system or floor with crawl space) where the floor is not affected by any movement of the subsoils beneath the floor. The loads of this floor system are supported on grade beams or structural beams that are then supported on drilled underreamed piers.

1.3.4 Recommended Foundation System – Continuous Footing/Grade Beams Provided the site and subgrade preparation recommendations provided in Section 1.3.1 of this report are followed and at least 1.5 feet of properly compacted select fill is placed over the foundation area and to a distance of at least five (5) feet beyond the perimeters of the foundation, it is our opinionthat the planned building construction can also be supported on a conventional continuous footing and/or grade beam foundation system. To achieve the required finished grade, it may be necessary that the existing subgrade be over-excavated to a depth that will allow the placement of the recommended thickness of select fill soils. Foundations bearing on the properly compacted select fill soil should be placed at least two (2) feet below finished grade and be designed for a net allowable bearing pressure of 2,000 psf for dead load plus sustained live loads and 3,000 psf for dead loads plus sustained and transient live loads, whichever results in a larger bearing area. These values consider a safety factor of at least 3 and 2, respectively, against a bearing capacity failure.

Footing foundations should be prepared by excavating the overburden soils to the final foundation grade elevation, compacting the foundation subgrade soils to an in-place dry density equal to at least 95% of the maximum dry density at a moisture content within 2% of the optimum moisture content as determined by ASTM D 698. A tamping plate hand compactor or othersuitable impact compactor should be used to perform the compaction.Without proper compaction of the spread footing/grade beam foundation soils, settlement of the shallow spread/grade beam footings could exceed 1 inch.

The foundation excavations should be observed by a representative of All-Terra Engineering, Inc. or qualified personnel prior to steel or concrete placement to assess that the foundation materials are capable of supporting the design loads and are consistent with the materials discussed in this report. Soft, loose, or unstable soil zones encountered at the bottom of the footing


excavations should be removed and replaced with properly compacted select fill as directed by the geotechnical engineer.

After opening, footing excavations should be observed and concrete placed as quickly as possible to avoid exposure of the footing bottoms to wetting and drying. Surface run-off water should be drained away from the excavations and not be allowed to pond. The foundation concrete should be placed during the same day the excavation is made. If it is required that footing excavations be left open for more than one day, they should be protected to minimize evaporation or entry of moisture.

• Slab-on-Grade FloorThe floor for the proposed residential building may consist of a slab-on-grade floor with site preparation performed as described above in Section 1.3.1 of this report. An allowable net bearing pressure of 600 psf can be used for slab-on-grade bearing on properly compacted select fill. It is suggested that cushion sand (leveling sand) not be placed within the area of the slab-on-grade floor. If cushion sand becomes wet, erosion, and/or settling of the sand may occur which can result in the formation of voids beneath the floor and associated structural distress.

1.3.5 Recommended Foundation System – Shallow Spread FootingsProvided the site and subgrade preparation recommendations provided in Section 1.3.1 of this report are followed and at least 1.5 feet of properly compacted select fill is placed over the foundation area and to a distance of at least five (5) feet beyond the perimeters of the foundation, it is our opinion that the planned building construction can also be supported by shallow spread footings. To achieve the required finished grade, it may be necessary that the existing subgrade be over-excavated to a depth that will allow the placement of the recommended thickness of select fill soils. The shallow spread footings should have a maximum width of about 5 feet, be founded at a depth of at least 3 feet below the desired finished grade and be designed for maximum allowable net bearing pressures of 2,400 psf for axial compression dead loads plus sustained loads and 3,600 psf for axial compression dead loads plus sustained and transient live loads.

If a cluster of closely spaced footings (i.e., if the center to center spacing of the footings is less than two times the width of the footing) are planned, All-Terra Engineering, Inc. should be contacted to calculate the amount of settlement.

Footing foundations should be prepared by excavating the overburden soils to the final foundation grade elevation, compacting the foundation subgrade soils to an in-place dry density equal to at least 95% of the maximum drydensity at a moisture content within 2% of the optimum moisture content as determined by ASTM D 698. A tamping plate hand compactor or other suitable impact compactor should be used to perform the compaction.


Without proper compaction of the spread footing/grade beam foundation soils, settlement of the shallow spread/grade beam footings could exceed 1 inch. The foundation excavations should be observed by a representative of All-Terra Engineering, Inc. or a qualified personnel prior to steel or concrete placement to assess that the foundation materials are capable of supporting the design loads and are consistent with the materials discussed in this report.Soft, loose, or unstable soil zones encountered at the bottom of the footing excavations should be removed and replaced with properly compacted selectfill as directed by the geotechnical engineer.

After opening, footing excavations should be observed and concrete placed as quickly as possible to avoid exposure of the footing bottoms to wetting and drying. Surface run-off water should be drained away from the excavations and not be allowed to pond. The foundation concrete should be placed during the same day the excavation is made. If it is required that footing excavations be left open for more than one day, they should be protected to minimize evaporation or entry of moisture.

• Slab-on-Grade FloorThe floor for the proposed residential building may consist of a slab-on-grade floor with site preparation performed as described above in Section1.3.1 of this report. An allowable net bearing pressure of 600 psf can be used for slab-on-grade bearing on properly compacted select fill. It is suggested that cushion sand (leveling sand) not be placed within the area of the slab-on-grade floor. If cushion sand becomes wet, erosion, and/or settling of the sand may occur which can result in the formation of voids beneath the floor and associated structural distress.

• Structural FloorAs an alternative to the use of a slab-on-grade floor and placement ofselect fill soil, the floor for the proposed residential building may also consist of a floor placed over void boxes or an elevated floor system (structural floor system or floor with crawl space) where the floor is not affected by any movement of the subsoils beneath the floor. The loads of this floor system are supported on grade beams or structural beams that are then supported on shallow spread footings.

2.0 FIELD INVESTIGATION

For this geotechnical investigation, a total of 2 geotechnical borings were drilled and sampled on March 21, 2019 at the locations shown on Plate No. 2. Drilling, sampling, and testingwere performed in accordance with applicable ASTM procedures using conventional auger drilling methods. Soil sampling during the drilling of the geotechnical borings consisted of continuous sampling to a depth of 10 feet and sampling on 5-foot intervals thereafter, with both disturbed and relatively undisturbed samples being obtained.


Relatively undisturbed samples were obtained by hydraulically forcing sections of 2.25-inch O.D. tubing (Shelby tube) into the subsoils. The tube samples were extruded in the field, sealed with foil, and placed into airtight plastic bags. Estimates of the unconfined compressive strengths of the cohesive soils were obtained with pocket penetrometer readings being taken on the tube samples.

Disturbed samples of soils were taken from the flight auger of the sampler. The samples recovered were removed from the auger of the sampler, visually classified, and placed into airtight plastic bags.

All samples were transported to All-Terra Engineering, Inc. laboratory for purposes of performing laboratory tests on selected samples.

3.0 LABORATORY TESTING

For the current geotechnical study, a laboratory testing program was conducted to obtain engineering properties for use in performing engineering analyses and to adjust field soil classifications. The following laboratory tests were performed:

LABORATORY TEST TEST STANDARD

Moisture Content of Soils ASTM D 2216

Moisture Content and In Situ Dry Density of Soils ASTM D 2937

Percent Soil Particles Passing a No. 200 Sieve ASTM D 1140

Liquid Limit, Plastic Limit, and Plasticity Index of Soils ASTM D 4318

The number of tests and the test results are presented in the attached boring logs for Boring Nos. B-1 and B-2 in the Appendix. All tests were performed in accordance with applicable ASTM procedures and methods and soil classifications were completed in accordance with the procedures and guidelines of ASTM D 2487 and ASTM D 2488.

4.0 FOUNDATION MAINTENANCE

Differential movements usually result from non-uniform changes in soil moisture that may result from climatic and non-climatic factors. Design methods for slab-on-grade construction consider only climatic factors and are based on average climatic conditions being present before construction and throughout the structure life. Maintaining balanced soil moisture conditions throughout the life of the structure reduces the potential for differential movements.

Factors unrelated to climate may result in soil movements that may be greater than those resulting only from climatic influence. The presence or absence of many non-climatic


factors is generally beyond the direct influence of the design team. The non-climatic factors are often manifested during the structure life.

Non-climatic factors that affect soil moisture include trees (present and removed) and landscaping, inadequate or altered drainage during the structure life, and the availability of moisture from unplanned sources such as roof drains, air conditioning drains, or below-grade utility or irrigation system leaks. Non-climatic factors and their potential effects on structure performance are discussed in the following paragraphs.

Trees and Landscaping

Trees and other landscaping have dynamic effects on soil moisture content. As a tree or other landscaping grows and matures, an increasing amount of moisture is needed to sustain its growth. If sufficient moisture in unavailable from infiltration of water from the surface, either through rainfall or irrigation, the moisture within the soil becomes the available source resulting in decreases in the soil moisture content and soil shrinkage adjacent to trees. The lower moisture contents generally are observed throughout the area of influence of the tree's root system. The lateral extent where moisture changes occur is generally taken as canopy width of the tree.

A uniform reduction in moisture usually does not occur; the changes in moisture content are often greatest near the tree and decrease with distance from the tree. The vertical extent of moisture changes caused by trees is not well defined since little information is known about the suction potential of trees in the area. From forensic investigations, the depth of influence appears to extend below 6 feet to 8 feet and may extend to 12-foot to 15-foot depths for large, mature trees. Trees should be located a distance away from the foundation at least equal to the mature height of the tree. Tree selection should consider the water capacity needed to sustain a mature tree. Irrigation systems may not be effective in supplying sufficient water for growth.

Drainage

Improper drainage can have significant negative effects on structure performance, especially if the structure was constructed during or immediately after a dry period. The following are general notes concerning proper drainage considerations:

• Positive drainage away from the structure must be designed, constructed, and maintained throughout the structure life.

• Landscaping systems must be laid out to provide/maintain positive drainage away from the structure and not permit water to impound adjacent to the structure.

• Downspouts from roof drainage systems should be designed to discharge water away from the structure foundation.


• Drainage through drainpipes to the storm sewer is preferred for all roof drains. Splash blocks are not effective in draining water away from the foundation and should not be used.

• Water drains should be tied into the storm sewer and not allowed to drain along the face of the building with discharge at/near the building foundation.

5.0 CONSTRUCTION CONSIDERATIONS

The following recommendations should be followed with regard to construction of the proposed residence:

• Fill material and fill compaction should comply with the recommendations provided in Section 1.3.1 of this report.

• Construction operations should be monitored by a representative of the geotechnical engineer or the owner’s representative.

• Materials testing should be performed to assure that acceptable materials and construction methods are provided by the contractor.

6.0 CLOSING REMARKS

All-Terra Engineering, Inc. has performed a geotechnical investigation pertaining to the design and construction of the proposed residence that will be constructed at 7900 Cora Street (Lots 3, 4, & 5 in Block 18 at Highland Addition, HCAD 0162610180003) in Houston, Texas. This report has been prepared for the exclusive use of the City of Houston Housing& Community Development Procurement Services and its authorized representatives inaccordance with generally accepted soil and foundation engineering practices. No other warranty, expressed or implied, is made.

In the event that changes are made in the nature, design, or location of the proposed residential development, the conclusions, parameters, and recommendations contained in this report shall not be considered valid unless the changes are reviewed and the findings/recommendations of this report are modified or verified in writing. The analyses and recommendations presented in this report are based upon data obtained from 2 geotechnical borings drilled on March 21, 2019. The nature and extent of variations within the subsurface materials may not become evident until after construction is initiated. If significant variations in the subsurface materials are encountered during construction, it may be necessary to re-evaluate the recommendations provided in this report.

APPENDIX

Plate Nos. 1 through 5

04/01/19

Project No:

AE19-803-08

Plate No. 16200 Rothway, Ste 140 Houston, Texas 77040 Date:

Proposed Residence7900 Cora Street

Houston, Texas 77088

VICINITY MAPN

SITE LOCATION

6200 Rothway, Ste 140 Houston, Texas 77040 Date: 04/01/19 BORING LOCATIONS Plate No. 2

Proposed Residence Project No:7900 Cora Street AE19-803-08

Houston, Texas 77088N

- Geotechnical borings included in the study.

B-1B-2

LOTS 3, 4, & 5, BLOCK 18 HIGHLAND ADDITION

of 1PROJECT: Proposed Residence BORING NO.: B-1

7900 Cora Street BORING LOCATION: See Plate No. 2(Lots 3, 4, & 5, Block 18, Highland Addition) BORING TYPE: Auger

PROJECT LOCATION: Houston, Texas 77088 APPROX. ELEVATION: NA ft-MSLPROJECT NO.:

CLIENT: City of Houston Housing and Community Development DATE:

LL PL PI

SANDY LEAN CLAY (CL), stiff to very stiff,1 gray

2

3

4 - light gray at 4'

5

6

7

8 - light gray and tan at 8'

9

10

11

12

13 13'

FAT CLAY (CH), very stiff, gray and reddish14 brown

15

16

17 17'

: : SILTY SAND (SM), tan18 : :

: :19 : :

: :20 : : 20'

17.1

Groundwater = 13.0' during drilling and was measured at a depth of 8.5' after the completion of drilling. The boring was backfilled w/ soil cuttings after the completion of the drilling activities. Plate No. 3

(Boring terminated at 20')

67.135 15

4.00 21.2

16.93.50

2.50 16.2

1.50 16.9

1.50 17.1 29 14 15

COM

PRES

SIV

E ST

REN

GTH

(T

SF)

AE19-803-08March 21, 2019

DEP

TH, F

T.

SAM

PLE

SOIL

TY

PE

DESCRIPTION OF STRATUM

HA

ND

PEN

. RE

AD

ING

(TSF

)

SPT

BLO

WS

(PER

6")

DRY

DEN

SITY

(P

CF)

31

60.4

16.7 15 16

20

J

LOG OF BORING

ATTERBERG LIMITS (%)

PASS

#20

0 SI

EVE,

%

2.00

MO

ISTU

RE

CON

TEN

T, %

of 1PROJECT: Proposed Residence BORING NO.: B-2

7900 Cora Street BORING LOCATION: See Plate No. 2(Lots 3, 4, & 5, Block 18, Highland Addition) BORING TYPE: Auger

PROJECT LOCATION: Houston, Texas 77088 APPROX. ELEVATION: NA ft-MSLPROJECT NO.:

CLIENT: City of Houston Housing and Community Development DATE:

LL PL PI

SANDY LEAN CLAY (CL), firm to very stiff,1 gray

2

3

4 - light gray at 4'

5

6

7

8 - light gray and tan at 8'

9

10

11

12

13 13'

FAT CLAY (CH), very stiff, gray and reddish14 brown

15 15'

LOG OF BORING

AE19-803-08March 21, 2019

DEP

TH, F

T.

SAM

PLE

SOIL

TY

PE

DESCRIPTION OF STRATUM

HA

ND

PEN

. RE

AD

ING

(TSF

)

SPT

BLO

WS

(PER

6")

MO

ISTU

RE

CON

TEN

T, %

ATTERBERG LIMITS (%)

PASS

#20

0 SI

EVE,

%

DRY

DEN

SITY

(P

CF)

COM

PRES

SIV

E ST

REN

GTH

(T

SF)

17.91.00

31 16 15 61.32.00 17.8

2.00 15.5

2.50 16.5 31 15 16

2.50 16.5

4.00 17.4

Groundwater = 12.0' during drilling and was measured at a depth of 9.0' after the completion of drilling. The boring was backfilled w/ soil cuttings after the completion of the drilling activities. Plate No. 4

(Boring terminated at 15')

Slickensided ------- Having planes of weakness that appear slick and glossy. The degree of slickensidedness dependsupon the spacing of slickensides and the ease of breaking along these planes.

Fissures ------------- Containing shrinkage or relief cracks, often filled with fine sand or silt; usually more or less vertical.Pocket --------------- Inclusion of material of different texture that is smaller than the diameter of the sample.Parting --------------- Inclusion less than 1/8 inch thick extending through the sample. NO JARSeam ----------------- Inclusion 1/8 inch to 3 inches thick extending through the sample. SAMPLE SAMPLELayer ----------------- Inclusion greater than 3 inches thick extending through the sample.Laminated ---------- Soil sample composed of alternating partings or seams of different soil types.Interlayered---------- Soil sample composed of alternating layers of different soil types.Intermixed ---------- Soil sample composed of pockets of different soil types and layered or laminated structure is not

evident. SHELBY SPTCalcareous--------- Having appreciable quantities of carbonate. TUBE

Number of blows for each 6-inch increment of split spoon penetration.Number of blows of split spoon penetration for the indicated depth of penetration in inches.

MAJOR LETTER TYPICALDIVISIONS SYMBOL DESCRIPTIONS

GRAVEL & CLEAN WELL GRADED GRAVEL, GRAVEL-SAND Degree Plasticity IndexCOARSE GRAVELY GRAVEL MIXTURES WITH LITTLE OR NO FINES None - - - - - - 0 - 4GRAINED SOILS (LITTLE OR POORLY GRADED GRAVEL, GRAVEL-SAND Slight - - - - - - 5 - 10

SOILS LESS THAN NO FINES) MIXTURES WITH LITTLE OR NO FINES Medium - - - - - - 11 - 20LESS 50% PASSING W/ APPRECIABLE SILTY GRAVEL, GRAVEL-SAND-SILT MIXTURES High - - - - - - 21 - 40THAN NO. 4 SIEVE FINES GC CLAYEY GRAVELS, GRAVEL-SAND-CLAY MIXTURES Very High - - - - - - > 4050% SANDS CLEAN SANDS SW WELL GRADED SAND, GRAVELY SAND (LITTLE FINES)

PASSING MORE THAN LITTLE FINES SP POORLY GRADED SANDS, GRAVELY SAND (L.FINES)

NO. 200 50% PASSING SANDS WITH SM SILTY SANDS, SAND-SILT MIXTURES Very Soft - - - - - - < 0.25 ksfSIEVE NO. 4 SIEVE APPRECIABLE FINES SC CLAYEY SANDS,SAND-CLAY MIXTURES Soft - - - - - - ksf

INORGANIC SILTS & VERY FINE SANDS,ROCK FLOUR Firm - - - - - - ksfFINE SILTS AND CLAYS SILTY OR CLAYEY FINE SANDS OR CLAYEY SILT W/ LOW PI Stiff - - - - - - ksf

GRAINED LIQUID LIMIT INORGANIC CLAY OF LOW TO MEDIUM PI LEAN CLAY Very Stiff - - - - - - ksfSOILS LESS THAN 50 GRAVELY CLAYS, SANDY CLAYS, SILTY CLAYS Hard - - - - - - ksfLESS OL ORGANIC SILTS & ORGANIC SILTY CLAYS OF LOW PI

THAN INORGANIC SILTS, MICACEOUS OR DIATOMACEOUS

50% SILTS AND CLAYS FINE SANDY OR SILTY SOILS, ELASTIC SILTS

PASSING LIQUID LIMIT INORGANIC CLAYS OF HIGH PLASTICITY

NO. 200 50 OR GREATER FAT CLAYS SPT (bpf)SIEVE OH ORGANIC CLAYS OF MED TO HIGH PI, ORGANIC SILT Very Loose 0 - 4 0 - 0.50

PEAT AND Loose 5 - 10 0.50 - 1.50OTHER HIGHLY ORGANIC SOILS Med. Dense 11 - 30 1.50 - 4.00

Dense 31 - 50Very Dense > 50

3/4"BOUL- GRAVEL SAND-DERS

152 76.2 19.1 4.76 2.0 0.42 0.074

NOTES: The boring logs and related information depict subsurface conditions only at the specific locations and dates indicated. Soil conditions and water levels at other locations may differ from conditions occuring at these boring locations. Also the passage of time may result in a change in the conditions at these boring locations. REFERENCES: (1) Soil Mechanics in Engineering Practice, Terzhagi and Peck, 1967 (2) ASTM D 422 Plate No. 5

TERMS AND SYMBOLS USED ON BORING LOGS

SOIL STRUCTURE SAMPLER TYPE

J

SPLIT-SPOON SAMPLER DRIVING RECORD GROUNDWATER DATABlows Per Foot Water Level after 24 hours.

8-10-1250/5"

Water level during drilling.

UNIFIED SOIL CLASSIFICATION SYSTEM - ASTM D 2487COHESIVE SOILS (1)

A) Degree of Plasticity

GW

GP

GM

B) Unconfined Compressive Strength

0.25 - 0.50

ML0.50 - 1.001.00 - 2.00

CL2.00 - 4.00

> 4.00

MH GRANULAR SOILS (1)

HIGHLY ORGANIC SOIL PT

UNCLASSIFIED FILL MATERIALS ARTIFICIALLY DEPOSITED AND OTHER UNCLASSIFIED SOILS AND MANMADE SOIL MIXTURES

4.00 - 4.50> 4.50

No.4 No.10 No.40

CH Density/ConsistencyPP (tsf)

COARSE MEDIUM FINE

bpf = blows/ft

CLASSIFICATION OF GRANULAR SOILS (2)U.S. STANDARD SIEVE SIZE(S)

6" 3"

0.005 0.001GRAIN SIZE IN MM

No.200

COBBLES SILT CLAYCOARSE FINE

TERRA ENGINEERING, INC.

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