Attachment 6 Geotech Report Through Supplement 1.pdf

Geotechnical Engineering Study

IMPROVEMENTS TO THE

KNIPLING-BUSHLAND U.S. LIVESTOCK

INSECTS RESEARCH LABORATORY

(KBUSLIRL) SITE

Kerrville, Texas

Arias Job No. 2018-933

Prepared For Merrick & Company

May 29, 2019 (Revised July 3, 2019)

ARIAS

GEOPROFESSIONALS

142 Chula Vista, San Antonio, Texas 78232 • Phone: (210) 308-5884 • Fax: (210) 308-5886

May29 ,2019 (Revised July 3, 2019) Arias Job No. 201 8-933 VIA Email: ion.delay@merrick.com

Mr. Jon C. DeLay P.E.

Merrick & Company 5970 Greenwood Plaza Blvd Greenwood Village, Colorado 80111

RE: Geotechnical Engineering Study

USDA ARS KBUSLIRL

Kerrville, Texas

Dear Mr. DeLay:

This report presents the results of a Geotechnical Engineering Study for the proposed new buildings and pavement to be constructed at the Knipling-Bush land U.S. Livestock Insects Research Laboratory (KBUSLIRL) in Kerrville, Texas. This study was authorized by the signed Subcontract Agreement for Professional Services between Merrick & Company and Arias & Associates, Inc. on April 5, 2019 and in accordance with Arias proposal 2019-933 dated October 26, 2018 and revised on November 9, 2018.

The purpose of this geotechnical engineering study was to establish foundation and pavement engineering properties of the subsurface soil and groundwater conditions present at the site. The scope of the study is to provide geotechnical engineering criteria for use by design engineers in preparing the foundation and pavement design. Our findings and recommendations should be incorporated into the design and construction documents for the proposed development.

The long-term success of the project will be affected by the quality of materials used for construction and the adherence of the construction to the project plans and specifications. The quality of construction can be evaluated by implementing Quality Assurance (QA) testing. As the Geotechnical Engineer of Record (GER), we recommend that the earthwork, foundations, and pavement construction be tested and observed by Arias in accordance with the report recommendations. A summary of our qualifications to provide QA testing is discussed in the “Quality Assurance Testing” section of this report. Furthermore, a message to the Owner with regard to QA testing is provided in the GBA publication included in Appendix E.

We appreciate the opportunity to serve you during this stage of site development. If we may be of further service, please call.

Sincerely, ARIAS & ASSOCIATES, INC.

TBPE Registration No. F-32 ~J’~•~ 4

• *~ A~? 1ç~g ~~ erry D. ~ hephe~~GE ~~ Ch~oer. Szy~E.

Senior Geotechnical Engineer ~°~‘ 112142 Senior Geotechnical Engineer

Austin • Corpus risti • • Fort Worth • San Antonio

Arias Geoprofessionals i Arias Job No. 2018-933

REPORT FORMAT INFORMATION

To improve clarity in the intent of our geotechnical recommendations for this project, the report is organized into two separate, but equally important sections.

Section I – Synopsis is a summary of our geotechnical recommendations specific to this project.

Section II – The Main Report contains more detailed information including foundation and pavement design parameters and site work recommendations.

A study of both of the above referenced sections is recommended for the Project Team Members.

Arias & Associates, Inc. cautions that Section I, Synopsis, is a consolidated quick reference overview of the more detailed geotechnical recommendations contained in Section II and should not be used exclusively from the remainder of the report.

Arias Geoprofessionals I- Arias Job No. 2018-933

REPORT FORMAT INFORMATION ...................................................................................... i

SECTION I: SYNOPSIS ....................................................................................................... I-1

SECTION II: GEOTECHNICAL REPORT ..............................................................................II-1

PROJECT DESCRIPTION .................................................................................................II-1

SCOPE OF SERVICES ......................................................................................................II-1

SOIL BORING AND LABORATORY TESTING ..................................................................II-1

LABORATORY TESTS ......................................................................................................II-2

SUBSURFACE CONDITIONS ...........................................................................................II-3

Site Stratigraphic and Engineering Properties ..............................................................II-4 Groundwater.................................................................................................................II-6

MOISTURE VARIATIONS AND ESTIMATED MOVEMENT ...............................................II-7

FOUNDATION DESIGN CONSIDERATIONS ....................................................................II-7

Recommended Building Pad Improvement for 1” PVR .................................................II-7 Stiffened Beam and Slab on Grade ..............................................................................II-8 Building Pad Construction .......................................................................................... II-11 Mat Foundations ......................................................................................................... II-11

ADDITIONAL DESIGN CONSIDERATIONS .................................................................... II-12

Flatwork Considerations ............................................................................................. II-12 Design Measures to Reduce Changes in Soil Moisture .............................................. II-12 IBC Site Class Determination ..................................................................................... II-13 Utilities ........................................................................................................................ II-14 Slab-Bearing Partition Walls & Flooring ...................................................................... II-14 Control and Construction Joints .................................................................................. II-14

PAVEMENT RECOMMENDATIONS ................................................................................ II-14

Pavement Design Parameters and Assumptions ........................................................ II-14 Curb and Gutter .......................................................................................................... II-15 Site Drainage .............................................................................................................. II-15 Demolition of Existing Pavements and Site Preparation ............................................. II-15 Pavement Fill Requirements ....................................................................................... II-16 Rigid Concrete Pavement Joints ................................................................................. II-16 Performance Considerations ...................................................................................... II-17 Pavement Subgrade and Section Materials ................................................................ II-17

CONSTRUCTION CRITERIA ........................................................................................... II-20

Site Preparation .......................................................................................................... II-20 Earthwork and Foundation Acceptance ...................................................................... II-21

GENERAL COMMENTS .................................................................................................. II-21

Arias Geoprofessionals I-i Arias Job No. 2018-933

Geotechnical Design Review ...................................................................................... II-21 Subsurface Variations ................................................................................................ II-22 Quality Assurance Testing .......................................................................................... II-22 Standard of Care ........................................................................................................ II-23

APPENDIX A: FIGURES AND SITE PHOTOGRAPHS ........................................................... A-1

APPENDIX B: BORING LOG AND KEY TO TERMS .............................................................. B-1

APPENDIX C: LABORATORY AND FIELD TEST PROCEDURES ......................................... C-1

APPENDIX D: GBA INFORMATION ....................................................................................... D-1

APPENDIX E: PROJECT QUALITY ASSURANCE ................................................................. E-1

Tables

Table 1: Project Description .................................................................................................... I-1 Table 2: Existing Conditions during Geotechnical Study ......................................................... I-1 Table 3: Building Pad Recommendations for 1-inch Design PVR ............................................ I-2 Table 4: Recommended Pavement Sections .......................................................................... I-3 Table 5: Project Compaction, Moisture and Testing Requirements ......................................... I-4 Table 6: Boring Depths ...........................................................................................................II-1 Table 7: Soluble Sulfate Test Results .....................................................................................II-3 Table 8: Existing Pavement Structure .....................................................................................II-4 Table 9: Generalized Subsurface Conditions - Buildings .........................................................II-5 Table 10: Generalized Subsurface Conditions – Pavement.....................................................II-6 Table 11: Groundwater Measurements ...................................................................................II-6 Table 12: Potential Vertical Rise (PVR) Results ......................................................................II-7 Table 13: BRAB and WRI Foundation Design Criteria .............................................................II-9 Table 14: PTI Slab-on-Grade Soil Design Criteria (3rd Edition) .............................................. II-10 Table 15: Allowable Bearing Pressure and Beam Penetration .............................................. II-10 Table 16: IBC Site Classification and Seismic Design Parameters ........................................ II-13 Table 17: Pavement Design Parameters and Assumptions ................................................... II-14 Table 18: Pavement Subgrade Materials .............................................................................. II-17 Table 19: Fill Requirements and Subgrade Treatment Options ............................................. II-18 Table 20: Subgrade Treatment Option - Lime Treatment ...................................................... II-19 Table 21: Flexible Pavement Requirements .......................................................................... II-19 Table 22: Rigid Pavement Section Materials ......................................................................... II-20 Table 23: Site Work (Non-Structural/General Fill) Requirements .......................................... II-21

Arias Geoprofessionals I-1 Arias Job No. 2018-933

SECTION I: SYNOPSIS

This synopsis includes a brief description of the project, subsurface findings, client-preferred foundation type, and generalized earthwork requirements for building pads and foundation and pavement design, as well as specific items of concern from a geotechnical standpoint for consideration during the design, construction, and maintenance phases of this project.

Table 1: Project Description

Project USDA ARS KBUSLIRL New Buildings and Pavement

Project Location Kerrville, Texas

Proposed Development Five (5) New 1- story structures with associated parking areas and driveways

Anticipated Building Foundation Type Stiffened Beam and Slab on Grade or Mat Foundation

Table 2: Existing Conditions during Geotechnical Study

Existing Surface Conditions Some grass area, with existing buildings and pavement

Predominant Soil/Rock Types Terrace Deposits and Residual soil layer (about

10 to 20 feet thick, but variable) at surface overlying Marlstone from Glen Rose Formation

Depth to Groundwater Groundwater at approximately 4’ in boring 14 and 15’ in boring 7.

Estimated Existing Potential Vertical Rise (PVR)

Approximately 1 to 1½ inches

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Table 3: Building Pad Recommendations for 1-inch Design PVR

Client-Preferred Foundation Type: Stiffened Beam and Slab on Grade

Site Improvement Method: Undercut & Replace with Imported Select Fill

Improved Site Condition (PVR): 1-inch design PVR

Minimum Undercut Depth: At least 2 feet

Scarify, Moisten & Compact Exposed Subgrade: 12 inches (maximum 6-inch compacted lifts)

Minimum Select Fill Thickness: At least 2 feet or greater amount of select fill as necessary to reach planned floor slab subgrade

Select Fill Type:

• Locally available pit run material with a liquid Limit ˂40%, PI 7-20, %200 ≥ 50%, maximum 3” particle size

• Top 6” should consist of base material meeting TxDOT Item 247, Type A, Grade 1 or 2

Moisture Barrier: See Note 6

Notes:

1. The building pad improvements will be used with a stiffened beam and slab on grade foundation system designed for a 1-inch PVR.

2. Following stripping operations, undercut at least two (2) feet of the existing soils from beneath the proposed building area. Undercutting should extend laterally to provide at least a 5-foot overbuild beyond the slab perimeter and to the width of any adjacent sidewalks or pavement wider than 5 feet. Some excavation of Marlstone may be required if encountered in order to have all foundations bearing on similar materials. It is critical that all foundation elements bear on similar materials in order to reduce the potential for differential movement.

3. It is essential that the exposed subgrade be thoroughly rolled with at least a 20-ton roller or heavily loaded dump truck weighing at least 20 tons in order to minimize the potential for post-construction settlements. A minimum of 20 passes should be performed with passes alternating in directions perpendicular to each other.

A representative of the Geotechnical Engineer should be present during proof rolling operations. Any area that yields under the roller loading should be undercut to the depth specified by the geotechnical engineer and replaced with compacted select fill as outlined in Table 3. If deleterious material, rubble, or debris is encountered, it should be removed to firmer materials and disposed of properly. The void should then be replaced with properly compacted select fill. It is important that the site preparation operations be observed and tested by one of our representatives to verify that these recommendations are followed. After proof rolling, the subgrade should be scarified to a depth of 12 inches, moisture conditioned and compacted in maximum 6-inch compacted lifts as specified in SECTION I, Table 5 (Project Compaction, Moisture and Testing Requirements).

4. For construction equipment access, and to help in providing a more “all-weather” working surface, the top 6 inches of select fill should consist of compacted crushed limestone base meeting the requirements of TXDOT Item 247, Type A, Grade 1or 2.

5. If additional select fill thickness is necessary to achieve final design grade, fill should consist of pit run select fill meeting the requirements outlined in Table 3.

6. A horizontal barrier should extend at least 10 feet horizontally beyond the perimeter of the foundation of the building addition. The barrier can consist of concrete or asphalt paving, concrete flatwork or at least 24” of compacted onsite or import clay (PI between 20 and 40). All joints within the pavement, flatwork, and at pavement/flatwork interfaces should be sealed. Any landscaping located within 10 feet of the structure foundation should be placed in watertight above-grade planter boxes with drainage discharge on top of adjacent flatwork/paving. We recommend that the perimeter grade beam be constructed to a depth of at least 24 inches to aid in reducing the potential for moisture fluctuation beneath the building pad. The final grade beam depth and recommended construction should be determined by the structural engineer. The slab vapor retarder plastic should be extended from beneath the slab down the inside face (building pad side) of the grade beam trench.

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Table 4: Recommended Pavement Sections

Layer Material

Flexible Asphaltic Concrete (See Note 5)

Rigid Concrete (see Note 5)

Parking Area & Light Duty

Access Drive, Truck Lane & Medium Duty

Parking Area & Light Duty

Access Drive, Truck Lane & Medium Duty

Surface HMAC/PCC 2½” 3” 6” 5” 7” 6”

Base Flexible Base 10” 8” 12” 10” --- --- --- ---

Subgrade

Moisture conditioned *Moisture conditioned flexible asphalt sections should also have Tensar TX-140 geogrid installed over the 6-inch moisture conditioned subgrade

6” -- 6” -- 6” -- 6” --

Lime Treated (Soluble Sulfate Tests must be performed prior to using any calcium-based treatment agent)

-- 6” -- 6” -- 6” -- 6”

Notes:

1. Periodic/preventative maintenance should be planned for to reduce deterioration of the pavement structure while aiding to preserve the investment.

2. Light duty areas include parking and drive lanes that are subjected to passenger vehicle traffic only. Light duty areas exclude entrance aprons and drives to the site and single access route drive lanes to parking areas.

3. Medium duty areas include entrance aprons and drives into the site, single access route drive lanes to parking areas, and areas where paving will be subjected to truck traffic. Medium duty areas exclude areas where tractor trailers may travel or park, dock areas, areas where trash collection vehicles may travel and load or unload.

4. Heavy duty areas include areas subjected to 18-wheel tractor trailers, trash collection vehicles, dumpster pads including loading and unloading areas, and areas where truck turning and maneuvering may occur. At least eight (8)-inch thick concrete is recommended for heavy duty pavement areas and is not shown in Table 4.

5. During the paving life, maintenance to seal surface cracks within concrete or asphalt paving and to reseal joints within concrete pavement should be undertaken to achieve the desired paving life. Perimeter drainage should be controlled to reduce the influx of surface water from areas surrounding the paving. Water penetration into base or subgrade materials, sometimes due to irrigation or surface water infiltration leads to pre-mature paving degradation. Curbs should be used in conjunction with paving to reduce potential for infiltration of moisture into the base course. Curbs should extend the full depth of the base course and should extend at least 3 inches into the underlying subgrade. The base layer should be tied into the area inlets to drain water that may collect in the base.

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6. Material specifications, construction considerations, and section requirements are presented under “Pavement Subgrade and Section Materials” included in Section II of this report.

Table 5: Project Compaction, Moisture and Testing Requirements

Description Material

Percent Compaction

Optimum Moisture Content Testing

Requirement Compaction Test TxDOT 113-E for gravelly soils, and TxDOT 114-

E for clayey soils

Building Pad Areas

Exposed subgrade at base of excavation Proof roll Observation

Scarified, Moistened & Compacted Exposed

Subgrade ≥ 95% 0% to +4%

1 per 5,000 SF;

min. 3 per lift

Select Fill:

(Material Meeting

Requirements Outlined previously in Table 3)

≥ 98% -1% to +3% 1 per 5,000 SF;

min. 3 per lift

Pavement Areas

Scarified, Moisture Conditioned On-site Soil

& Lime Treated (Subgrade)

≥ 95% 0 to +4% 1 per 5,000 SF;

min. 3 tests

General Fill (Onsite Material)

≥ 95% 0 to +4% 1 per 5,000 SF;

min. 3 per lift

Base Material ≥ 95%

(ASTM D 1557)

+3%

1 per 5,000 SF;

min. 3 per lift

Hot-mix asphaltic concrete

91% to 95% Theoretical Lab

Density

(TEX 207 F)

Not applicable 1 per 5,000 SF;

min. 3 per lift

Non- Structural

Areas (Outside

Building Pad)

General Fill (On-site Material)

≥ 95% 0% to +4% 1 per 10,000 SF;

min. 3 per lift

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SECTION II: GEOTECHNICAL REPORT

PROJECT DESCRIPTION

The proposed project consists of the construction of five (5) single-story structures and associated pavements. The site is located on the west side of Fredericksburg Road, and north of IH 10, northeast of Kerrville, Texas. A Site Vicinity Map is provided in Appendix A of this report. At the time of this report, we have not been provided with the structural loads for the structures.

SCOPE OF SERVICES

The purpose of this geotechnical engineering study was to provide geotechnical engineering recommendations for the building and pavement areas. Environmental studies were not a part of our scope of services, nor was the completion of local or global stability analysis of any retaining walls. Additionally, it was beyond our authorized service scope to develop excavation plans and design temporary shoring systems such as soil nail walls, since these relate to “means and methods” and are the responsibility of the Contractor.

SOIL BORING AND LABORATORY TESTING

A total of fourteen (14) borings were drilled on May 7, 8, and 17, 2019 at the approximate locations shown on the Boring Location Plan provided in Appendix A. Table 6 below presents the boring locations, depth and the occurrence of ground water.

Table 6: Boring Depths

Boring No. Structure Depth, feet Coordinates Groundwater

Depth, feet Latitude Longitude

B-1 Laboratory Building 20 30.074778 -99.109111 N/A

B-2 Laboratory Building 20 30.074572 -99.109344 N/A

B-3 Office / Admin Building 20 30.074389 -99.108833 N/A B-4 Office / Admin Building 20 30.074111 -99.109167 N/A

B-5 Maintenance Shop 20 30.074333 -99.111667 N/A

B-6 Fly / Tick Building 20 30.074056 -99.112361 N/A

B-7 Cattle Working Barns 20 30.073861 -99.111833 16.1

B-8 Staff Parking Lot 6 30.074833 -99.108861 N/A

B-9 Roadway Pavement 6 30.075389 -99.107861 N/A

B-10 Roadway Pavement (Staff Entry) 6 30.074333 -99.108611 N/A

B-11 Roadway Pavement (Visitor Entry) 6 30.072722 -99.109806 N/A

B-12 Roadway Pavement 6 30.074028 -99.109722 N/A

B-13 Roadway Pavement 6 30.074500 -99.111028 N/A

B-14 Roadway Pavement 6 30.072972 -99.111583 5

Arias Geoprofessionals II-2 Arias Job No. 2018-933

All the borings were drilled within the approximate footprints of the planned new buildings and in the approximate areas of planned new pavements, and were drilled and sampled in accordance with ASTM D1586 procedures for Split Spoon, and ASTM D 1587 for thin-walled tube, sampling techniques as described in Appendix C. A truck mounted drill rig using continuous flight augers together with the sampling tools noted were used to secure the subsurface soil samples.

Soil classifications and borehole logging were conducted during the exploration by one of our field-logging technicians under the supervision of our Project Geotechnical Engineer. Final material classifications, as seen on the attached boring logs (Appendix B), were determined by the Project Geotechnical Engineer based on laboratory and field test results and applicable ASTM procedures. A key to the terms and symbols used on the logs is also included in Appendix B.

LABORATORY TESTS

As a supplement to the field exploration, we provided laboratory testing to determine water content, Atterberg Limits, percent passing the No. 200 sieve, unconfined compressive strength of cohesive soils, and soluble sulfate content. The laboratory results are reported in the attached boring logs included in Appendix B, with the exception of the soluble sulfate results which are presented in the Table 7 below. The soil laboratory testing for this project was done in accordance with applicable ASTM procedures with the specifications and definitions for these tests listed in Appendix C.

Remaining soil samples recovered from this exploration will be routinely discarded following submittal of this report.

Sulfate Testing Results

Laboratory testing was conducted to determine the soluble sulfate content on six (6) selected samples recovered from the borings drilled at the site. Testing was performed in general accordance with TxDOT test method Tex-145-E “Determining Sulfate Content in Soils.” The results indicate that the soluble sulfate contents of the samples tested were about 180 to 220 parts per million (ppm).

The results are indicative of relatively low soil sulfate content at this site. Therefore, lime or cement treatment of the onsite soils could be considered for this site. However, additional testing would need to be performed once the subgrade soils are exposed prior to applying any type of calcium-based treatment. A summary of the sulfate test results is provided below in Table 7.

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Table 7: Soluble Sulfate Test Results

Boring No. Approx. Sample Depth, (ft.) Material Description Soluble Sulfate

Content, (ppm) B-9 0.5 to 2 SANDY LEAN CLAY (CL) 200

B-10 2 to 4 SANDY LEAN CLAY (CL) 200

B-11 0.5 to 2 CLAYEY SAND (SC) 180

B-12 2 to 4 CLAYEY SAND (SC) 220

B-13 0.5 to 2 CLAYEY SAND (SC) 200

B-14 2 to 4 CLAYEY GRAVEL(GC) 200

Note: Approximate sample depth is referenced from the existing ground surface at the time of the geotechnical field exploration performed on May 8, 2019.

SUBSURFACE CONDITIONS

Generalized stratigraphy and groundwater conditions are discussed in the following sections. The subsurface and groundwater conditions are based on conditions encountered at the boring locations to the depths explored.

Soil and rock conditions may vary between the sample boring locations. Transition boundaries, or contacts, noted on the boring logs to separate soil and rock types, are approximate. Actual contacts may be gradual and vary at different locations. If conditions encountered during construction indicate more variation than established as a result of this study, we should be contacted to evaluate the significance of the changed conditions relative to our recommendations.

Existing Pavement Section

Existing asphalt and flexible base material were observed at the boring locations which were performed through existing paved areas. The table below indicates the approximate asphalt and flexible base thicknesses encountered at each of the boring locations; variations should be expected away from the boring locations.

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Table 8: Existing Pavement Structure Boring No. Asphalt (in) Flexible Base (in) Total Thickness (in)

B-1 2.5 2.0 4.5

B-7 0.75 6.5 7.25

B-8 1.75 4.0 5.75

B-9 2.0 7.0 9.0

B-10 1.0 6.0 7.0

B-11 0.75 6.0 6.75

B-12 0.75 6.0 6.75

B-13 1.0 6.0 7.0

B-14 0.75 6.0 6.75

Site Stratigraphic and Engineering Properties

In general, the subsurface materials encountered at the project site consist of approximately 10 to 20 feet of Terrace Deposits (Qt) and residual soils, overlying Marlstone from the Glen Rose Formation (Kgr). The generalized stratigraphic conditions for the borings performed for this project are summarized below in Tables 9 and 10. It should be noted that not all strata were encountered at all borings and that subsurface conditions are subject to variations.

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Table 9: Generalized Subsurface Conditions - Buildings

Where: Depth - Stratum depth (ft.) from existing ground surface at the time of geotechnical study.

PI - Plasticity Index -No. 200 - Percent passing #200 sieve, % PP - Pocket Penetrometer Range (tsf) N - Standard Penetration Test (SPT) value, blows per foot ** - Blow Counts during seating penetration

* - Only one test -- - No test

Stratum Depth

(ft) Material Description PI

Range

- 200

Range

PP

Range N range

Pavement to

0.4 – 0.6

0.75’’ to 2.5’’ Asphalt 2.0’’ to 6.5’’ Base -- -- -- --

I 0 – 0.6 to 2 - 18

Dark brown, Tan, Brown –

CLAYEY GRAVEL (GC),

CLAYEY SAND with GRAVEL (SC), CLAYEY GRAVEL with

SAND (GC) – loose to very dense

13 - 26 35 - 47 1.0 - 2.25 5 - 65/11’’

II

0 - 18 to 10 - 20

Tan, Dark brown – SANDY LEAN CLAY with GRAVEL (CL), GRAVELLY LEAN CLAY with

SAND (CL), LEAN CLAY (CL),

LEAN CLAY with SAND (CL), LEAN CLAY with GRAVEL (CL), SILTY LEAN CLAY (CL) – firm to very hard

6 - 29 53 - 91 1.75 – 4.5+ 5 – **50/1’’

IIA

to

Tan, – LEAN CLAY with SAND (CL) – hard

(Only encountered in B-5) 19 62 -- 42

III

10 - 18 to 13 - 20

Tan – MARLSTONE – very hard 15* 44* -- **50/4’’ - **50/0’’

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Table 10: Generalized Subsurface Conditions – Pavement

Where: Depth - Stratum depth (ft.) from existing ground surface at the time of geotechnical study.

PI - Plasticity Index -No. 200 - Percent passing #200 sieve, % PP - Pocket Penetrometer Range (tsf) N - Standard Penetration Test (SPT) value, blows per foot ** - Blow Counts during seating penetration

* - Only one test -- - No test

Groundwater

A dry soil sampling method was used to obtain the soil samples at the project site. Groundwater was encountered in two (2) borings during the field exploration during May 7, 8, and 17, 2019 as shown in Table 11 below. The open boreholes were backfilled using soil cuttings generated from the drilling process.

Table 11: Groundwater Measurements

Boring ID Encountered During Drilling, Feet Encountered During Drilling, Feet B-7 16.1 14.7

B-14 5.0 3.7

Groundwater levels will often change significantly over time and should be verified immediately prior to construction. Water levels in open boreholes may require several hours to several days to stabilize depending on the permeability of the soils. Groundwater levels at this site may differ during construction because fluctuations in groundwater levels can result from seasonal conditions, rainfall, drought, or temperature effects. Pockets or seams of gravels, sands, silts or open fractures and joints can store and transmit “perched” groundwater flow or seepage.

Stratum Depth (ft) Material Description PI Range

- 200 Range

PP

Range

N range

Pavement to

0.5 – 0.75

0.75’’ to 2.0’’ Asphalt 4.0’’ to 7.0’’ Base -- -- -- --

I

0.56 – 0.58 to

Brown, Tan – CLAYEY SAND with

GRAVEL (SC), CLAYEY GRAVEL

with SAND (GC) – loose to very dense

10 - 25 27 - 49 4.5 - 4.5+ 7 - **50/6’’

II

0.5 – 0.75 to

Tan, Brown – SANDY LEAN CLAY with GRAVEL (CL), LEAN CLAY

(CL), LEAN CLAY with SAND (CL), SANDY LEAN CLAY (CL) – firm to very stiff

9 - 13 62 - 94 4.0 - 4.5+ 5 - 25

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Should dewatering become necessary, it is considered means and methods and is solely the responsibility of the contractor.

MOISTURE VARIATIONS AND ESTIMATED MOVEMENT

Structural damage can be caused by volume changes in expansive soils. Expansive soils can shrink when they lose water and swell (grow in volume) when they gain water. The potential for expansive soils to shrink and swell is typically related to the Plasticity Index (PI). Soils with a higher PI generally have a greater potential for soil volume changes due to moisture content variations. Surficial soils encountered at this site have a moderate potential to shrink and swell in volume depending on changing soil water content conditions during or after construction. The term swelling soils implies not only to the tendency to increase in volume when water is available, but also to decrease in volume or shrink if water is removed.

Several methods exist to evaluate swell potential of expansive clay soils. We have estimated potential heave utilizing the TXDOT method (Tex 124-E). Using the TXDOT method, and the results are in Table 12 below. PVR values were calculated based on the existing moisture conditions at the time of the sampling activities.

Table 12: Potential Vertical Rise (PVR) Results

Structures PVR Range Site Improvement

Buildings 1.0 – 1.5 2 feet remove and replace

It has been our experience that the PVR method can sometimes underestimate the potential shrink/swell movements. Fluctuations in the soil moisture content generated from climatic conditions (i.e., droughts or floods) or as a result of development (e.g., irrigation of landscaping in the immediate vicinity of the building, poor surface drainage, leaking plumbing or water lines) may result in greater shrink/swell movements than calculated.

FOUNDATION DESIGN CONSIDERATIONS

We understand that the buildings will be relatively lightly loaded and therefore recommend that the planned buildings be supported on either a stiffened beam and slab on grade foundation or a mat foundation. The project team may determine that another foundation type is desired for this project during the design phase. Should an alternate foundation type be desired, we should be contacted to provide additional geotechnical design data for the alternate foundation type as a Supplement to this Geotechnical Report.

Recommended Building Pad Improvement for 1” PVR

Due to the potential for soil movement at this site, if a soil supported slab foundation is to be used, subgrade improvement will be needed. A remove and replace of the existing soils with 2 feet of

Arias Geoprofessionals II-8 Arias Job No. 2018-933 select fill is the recommended option, in those areas where the grading requirements have not already removed the expansive surface soils. The fill used at this site should abide by all requirements detailed in Table 3, Section 1 of this report.

Building pad preparation requirements on expansive clay sites are dependent upon the soil moisture condition at the time of construction. Typically, the geotechnical engineer does not know the climate conditions that will exist at the time of construction since he does not know when the structure will be built. Therefore, having the geotechnical engineer retained to review site preparation recommendations and be an active participant in Team Meetings near the time of construction can often result in project cost savings since soil moisture conditions at the time of construction could be more accurately assessed. Additionally, it has been our experience that retaining the same firm for both geotechnical engineering services and construction materials testing is prudent since the geotechnical engineer is most familiar with site conditions and can quickly respond to field challenges.

Grade-supported foundation elements for the proposed building will require additional site improvement recommendations in order to reduce the PVR or soil shrink-swell potential of the expansive clays for a 1-inch PVR. In this area, a PVR of 1-inch is typically an acceptable amount of movement for structures of this type and the recommendations provided in this report are based on this assumption. Although this is a typically acceptable magnitude of movement in this area, it should be understood that a 1-inch PVR can result in some cracking requiring periodic maintenance; but the structural integrity of the building should be maintained. If project requirements dictate a different magnitude of PVR, we should be informed so that modifications to our recommendations may be made. Recommendations are presented in Table 3 shown in Section I and are valid only for a 1-inch design PVR.

In unpaved areas at the perimeter of the planned additions, a 2-foot thick clay cap (see Note 6, Table 3) should be constructed over the select fill overbuild. This clay cap should aid in reducing the chances for surface water from infiltrating into the more pervious select fill and pond on top of the underlying, less permeable clay subgrade. A PVR exceeding 1-inch can occur if water is allowed to readily pond on top of the clay subgrade beneath the select fill body. Clean onsite soils (PI of 20 to 40, if present) can be used to construct the clay cap. The clay cap should be moisture conditioned to between 0 and +4 percentage points of optimum moisture content and then compacted to at least 95 percent of the maximum dry density determined by ASTM D 698.

Stiffened Beam and Slab on Grade

A grid type beam and slab-on-grade is generally used to support structures upon expansive soils where soil conditions are relatively uniform, and where uplift and settlement can be tolerated. The intent of a stiffened beam and slab-on-grade foundation is to allow the structure and foundation to move up and down with soil movements while providing enough stiffness to limit differential movements within the superstructure to an acceptable magnitude.

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There are various design methods for use by the structural engineer to select the grade beams depths and beam spacing’s for this project. The foundations may be designed using the Building Research Board No. 33 (BRAB Report) as a guideline. Alternatively, the foundations may be designed based on the Design of Slab-On-Ground Foundations published by the Wire Reinforcement Institute, Inc. (WRI-August 1981). Provided in the following sections are design criteria for both methods.

Tables 13 and 14 below present the design criteria for the proposed buildings.

Table 13: BRAB and WRI Foundation Design Criteria

Design Method BRAB WRI

Design PVR 1” 1”

Climatic Rating (Cw) – Kerrville, Texas 16 16

Effective Plasticity Index for Site Improvement to 1 PVR 20 20

Support Index (C) 0.95 --

Soil/Climatic Rating Factor (1-C) -- 0.05

Unconfined Compressive Strength (tsf) 1.2 --

Note: The above design values assume that the building addition pad has been improved as outlined in this report for an approximate 1-inch design PVR.

A stiffened beam and slab on grade foundation may also be designed for these structures using the 3rd Edition of the Design of Post-Tensioned Slabs-on-Ground published by the Post- Tensioning Institute. These values were estimated from the “Volflo” computer program in consideration of the soil conditions in the area of the planned buildings. Provided in the following table are design criteria for this method for design PVR value of 1-inch.

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Table 14: PTI Slab-on-Grade Soil Design Criteria (3rd Edition)

Design PVR About 1 inch

Depth to Constant Soil Suction 15 Feet

Constant Soil Suction 3.8 pF

Edge Moisture Variation Distance Center Lift, em

Edge Lift, em

9.0 feet

4.7 feet

Differential Soil Movement Center Lift, ym Edge Lift, ym

1.2 inches

1.7 inches

Coefficient of Slab-Subgrade Friction, µ 0.75

Note: The above design values assume that the building pad has been improved as outlined in this report for an approximate 1-inch design PVR.

Arias is providing design values for BRAB, WRI, and PTI methods for the Structural Engineer’s consideration and possible use. Arias recommends the final design methodology for the planned foundation be selected by the project Structural Engineer based on his knowledge and experience with similar foundation conditions.

Table 15: Allowable Bearing Pressure and Beam Penetration

Allowable Bearing Pressure 2,000 psf

Bearing Stratum at Bottom of Grade Beams/Footings Compacted Select Fill

Min. Penetration of Beams/Footings Below Final Grade for Bearing Pressure Requirements

24 inches

Note: Actual beam depth should be determined by structural engineer. Minimum penetration below final grade is necessary to reduce scour potential and the potential for water penetration under the foundation

The grade beams/footings should be based at the recommended depth or deeper, founded within the compacted select fill, and should be designed for the allowable soil bearing capacity provided above. Grade beams may be thickened and widened at concentrated loads to serve as spread footings. The beams and widened columns should be a minimum of 10 and 12 inches wide, respectively, for shear resistance. The grade beams should extend at least 24 inches below final grade within the compacted select fill. It is critical that all grade beams bear in similar materials in order to reduce the potential for differential movements.

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We recommend that at least a 10-mil vapor retarder be used under the slab. The vapor retarder should conform to ASTM E1745, Class C or better and shall have a maximum water vapor permeance of 0.044 perms when tested in accordance with ASTM E96. A 10 mil Stego Wrap by Stego Industries LLC or other similar products meeting these requirements would be acceptable.

Building Pad Construction The building pad, plus a 5-foot overbuild or greater to include adjacent flatwork, should be stripped of vegetation and excavated, as necessary, to provide any fill material necessary to meet final grade. Any material needed to reach the finished grade should be as shown in Table 3, Section I. It is essential that, prior to the placement of select fill, the exposed subgrade area of the excavation should be proof rolled to identify any soft areas, if present. Proof rolling should be accomplished using a loaded dump truck weighing at least 20 tons. Weak or soft areas evidenced during proof rolling, should be over-excavated and replaced according to Tables 3 and 5.

Mat Foundations

A concrete mat foundation may be used to support the planned foundation loads. The mat foundation should be designed with an appropriate factor of safety to reduce the possibility of soil failure when subjected to axial and lateral loads. Furthermore, foundation movements must be within allowable/tolerable limits of the soil and structure. We recommended that the resultant load be situated in the middle one-third of the mat foundation.

In addition to axial and lateral loading conditions, the planned foundation will need to be designed to resist overturning moments. Lateral loads can be resisted by a uniform allowable passive pressure of 1,500 psf acting on the side of the mat foundation. An ultimate coefficient of friction across the mat foundation base of 0.3 can be used to aid in the resistance of ground line shear loading.

Overturning moments can be resisted by the weight of the foundation, the sustained weight/load from the structure, and any soil overlying the foundation. A soil unit weight of 120 pounds per cubic foot (pcf) may be assumed for onsite soils or select fill.

A mat foundation may be used to support the planned structures provided it is founded on an engineered fill pad and that the measures to reduce soil moisture change are implemented as outlined in the previous report sections. A mat foundation can be designed for a net allowable soil bearing pressure of 2,500 psf for a mat bearing at least two (2) feet below the finished floor elevation provided that the recommendations shown in Tables 3 and 5 are followed. The provided allowable bearing pressure includes a factor of safety against bearing capacity failure of at least

3. The modulus of the subgrade reaction can be taken as k = 100 pci.

The recommended bearing pressures have been selected to limit potential settlements of shallow foundations. Total settlements for shallow foundations designed using our recommended bearing pressures at this site are expected to be less than one (1) inch.

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If the shrink/swell movements will interfere with the performance of the planned structures, we recommend that deep, drilled pier foundations be considered to support the planned site structure and movement-sensitive structures. Any movement-sensitive foundation elements, including floor slabs, grade beams, and/or pier caps, should be structurally suspended above grade and fully supported on drilled pier foundations.

ADDITIONAL DESIGN CONSIDERATIONS

Flatwork Considerations

Minor differential movements between the planned structures and abutting sidewalks should be expected if the flatwork is supported on similar building pad conditions. Thus, we recommend that the flatwork be supported entirely on the improved building pad. Flatwork supported on unimproved, natural site conditions will result in flatwork movements on the order of the magnitudes reported in the PVR section that can result in significant cracking, joint separations, and a reversal in drainage as discussed subsequently.

We recommend that the flatwork and the structure be designed to include details that permit foundation movements without resulting in vertical separations and without distressing either element. Control joints should be included that include steel reinforcing to prevent vertical shear, but to allow bending.

The flatwork and abutting sidewalks should be designed and constructed to allow for positive drainage to be maintained away from the structure foundations. The planned site grading should allow for potential future differential movements and should never be allowed to reach a level condition or negative slope that promotes drainage toward the foundation. This reversal in drainage can direct moisture into the building envelope and can become a constant nuisance and maintenance issue. If the potential differential movements cannot be tolerated, the Owner should consider extending the foundation pad beneath the planned sidewalks and incorporate the flatwork as part of the foundation system.

Design Measures to Reduce Changes in Soil Moisture

To maintain performance of the proposed structures to a 1-inch PVR, measures must be included in the design to reduce moisture fluctuations of the soils under the slab-on-ground. Movements of foundation soil can be effectively reduced by providing horizontal and/or vertical moisture barriers around the edge of the slabs. Typically, the moisture barriers would consist of concrete flatwork or asphalt or concrete pavement placed adjacent to the edge of the building. An alternate approach would be a clay cap.

Although subgrade modification through excavation and replacement is recommended to reduce potential soil related foundation movements, the design and construction of a grade-supported foundation should also include the following elements:

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• Roof drainage should be controlled by gutters and carried well away from the structure.

The ground surface adjacent to the building perimeter should be sloped and maintained a minimum of 5% grade away from the building for 10 feet to result in positive surface flow or drainage away from the building perimeter.

• Hose bibs, sprinkler heads, and other external water connections should be placed well away from the foundation perimeter such that surface leakage cannot readily infiltrate into the subsurface or compacted fills placed under the slabs-on-ground.

• Trees or other vegetation over 6 feet in height should not be planted within 15 feet of the structure unless specifically accounted for in the foundation design. Our design recommendations do not account for trees within 15 feet of the structure.

• Paved areas around the structure are helpful in maintaining equilibrium within the soil water content. If possible, pavement and sidewalks should be located immediately adjacent to the building.

• Site work excavations should be protected and backfilled without delay to reduce changes in the insitu moisture conditions.

IBC Site Class Determination Section 1613 of the International Building Code (2015) requires that every structure be designed and constructed to resist the effects of earthquake motions, with the seismic design category to be determined in accordance with Section 1613 or ASCE 7. Site classification according to the International Building Code (2015) is based on the soil profile encountered to the 100-foot depth.

The stratigraphy at the site location was explored to a maximum 20-foot depth.

Rock materials having similar consistency were extrapolated to be present between the 20 and 100-foot depths. On the basis of the site class definitions included in the 2015 Code and the encountered generalized stratigraphy, we characterize the site as Site Class D.

Seismic design coefficients were determined using the on-line software, Seismic Hazard Curves and Uniform Response Spectra, version 5.1.0, dated February 10, 2011 accessed at (https://earthquake.usgs.gov/designmaps/us/application.php). Analyses were performed considering the 2015 International Building Code. Input included GPS coordinates and Site Class D. Seismic design parameters for the site are summarized in the following table.

Table 16: IBC Site Classification and Seismic Design Parameters

Site Classification Fa Fv Ss S1

D 1.6 2.4 0.057 g 0.028 g

Where: Fa = Site coefficient Fv = Site coefficient Ss = Mapped spectral response acceleration for short periods S1 = Mapped spectral response acceleration for a 1-second period https://earthquake.usgs.gov/designmaps/us/application.php

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Utilities

Utilities which go through the slab and beams should be designed with some flexibility to allow free movement in the lines.

Slab-Bearing Partition Walls & Flooring

Slab bearing partition walls and brittle floor tiles are susceptible to various degrees of cracking due to potential slab and foundation movements. Accordingly, the potential foundation movements cited earlier should be accounted for in the overall design.

Control and Construction Joints

Concrete, mortar, grout, and concrete or clay masonry units as well as numerous other construction materials shrink and swell upon a loss or gain of moisture in much the same manner as expansive soils. Accordingly, material volume changes or potential foundation movements can cause wall or slab cracking to occur. In general, however, unsightly cracking can normally be eliminated by controlling crack locations and making them inconspicuous so that they do not detract from the appearance of the building.