ESBD_384085_1734964033235_KL235009 - TAMUT GEOTECH.pdf

Report Cover Page

TAMU Golf Cart Storage Shed

Geotechnical Engineering Report

November 6, 2023 | Terracon Project No. KL235009

Prepared for:

Corgan Associates Inc.

401 North Houston Street

Dallas, Texas 75202

13145 Kallan Avenue

Tyler, Texas 75703

P (903) 593-7252

Terracon.com

Facilities | Environmental | Geotechnical | Materials

Report Cover Letter to Sign

November 6, 2023

Corgan Associates Inc.

401 North Houston Street

Dallas, Texas 75202

Attn: Mr. David Zatopek

P: (214) 749 2000

E: david.zatopek@corgan.com

Re: Geotechnical Engineering Report

TAMU Golf Cart Storage Shed

7101 University Avenue

Texarkana, Texas

Terracon Project No. KL235009

Dear Mr. Zatopek:

We have completed the scope of Geotechnical Engineering services for the above referenced project in general accordance with Terracon Proposal No. PKL235009, Revision 1 dated August 30, 2023. This report presents the findings of the subsurface exploration and provides geotechnical recommendations concerning earthwork and the design and construction of foundations, floor slabs, and pavements for the proposed project.

We appreciate the opportunity to be of service to you on this project. If you have any questions concerning this report or if we may be of further service, please contact us.

Sincerely, Terracon

(Texas Firm Registration No. F-3272)

Graham Welch, E.I.T. William M. Martin, P.E., APMP

Staff Engineer Senior Geotechnical Engineer

TAMU Golf Cart Storage Shed | Texarkana, Texas

Facilities | Environmental | Geotechnical | Materials i

Table of Contents Report Summary .............................................................................................. i

Introduction

Project Description

Site Conditions

Geotechnical Characterization

Groundwater Conditions

Seismic Site Class

Geotechnical Overview

Earthwork

Site Preparation

Subgrade Preparation

Excavation

Fill Material Types

Fill Placement and Compaction Requirements

Utility Trench Backfill

Grading and Drainage

Earthwork Construction Considerations

Construction Observation and Testing

Shallow Foundations

Design Parameters – Compressive Loads

Design Parameters – Overturning and Uplift Loads

Foundation Construction Considerations

Drilled Piers

Drilled Pier Design Parameters

Drilled Pier Lateral Loading

Drilled Pier Construction Considerations

Floor Slabs

Floor Slab Design Parameters

Floor Slab Construction Considerations

Structurally Suspended Floor Slabs

Pavements

General Pavement Comments

Subgrade Soil Treatment

Pavement Design Parameters

Pavement Section Thicknesses

Pavement Construction Specifications

Pavement Drainage

Pavement Maintenance

Pavement Design and Construction Considerations

General Comments

Facilities | Environmental | Geotechnical | Materials ii

Figures GeoModel

Attachments

Exploration and Testing Procedures

Site Location and Exploration Plans

Exploration and Laboratory Results

Supporting Information

Note: This report was originally delivered in a web-based format. Blue Bold text in the report indicates a referenced section heading. The PDF version also includes hyperlinks which direct the reader to that section and clicking on the logo will bring you back to this page. For more interactive features, please view your project online at client.terracon.com.

Refer to each individual Attachment for a listing of contents.

http://client.terracon.com/

Facilities | Environmental | Geotechnical | Materials i

Report Summary

Topic Overview Statement

Project

Description 1,200 square foot building with associated parking/driveway areas

Geotechnical

Characterization

Lean clay and fat clay at the surface underlain with clayey sand and silty sand

Groundwater observed at a depth of about 24 feet in Boring B-1 during our exploration

Earthwork 3 feet of structural fill recommended beneath the building floor slab to provide an estimated PVR of ¾ inches or less

Shallow

Foundations

Shallow foundations are recommended for building support

Allowable bearing pressure:

■ 2,000 psf for spread footings

■ 1,600 psf for continuous footings

Expected settlements: < 1-inch total, < ½-inch differential

Drilled Piers Drilled piers may be considered for support of the building. Design parameters for drilled straight shafts are provided in Drilled Piers.

Pavements

With subgrade prepared as noted in Earthwork.

Rigid or flexible pavement system may be used for this site.

Pavement section thicknesses and additional construction considerations provided in Pavements.

General

Comments This section contains important information about the limitations of this geotechnical engineering report.

1. If the reader is reviewing this report as a pdf, the topics above can be used to access the appropriate section of the report by simply clicking on the topic itself.

2. This summary is for convenience only. It should be used in conjunction with the entire report for design purposes.

Facilities | Environmental | Geotechnical | Materials 1

Introduction

This report presents the results of our subsurface exploration and Geotechnical

Engineering services performed for the proposed TAMU Golf Cart Storage Shed to be located at 7101 University Avenue in Texarkana, Texas. The purpose of these services was to provide information and geotechnical engineering recommendations relative to:

■ Subsurface soil conditions

■ Groundwater conditions

■ Seismic site classification per IBC

■ Site preparation and earthwork

■ Foundation design and construction

■ Floor slab design and construction

■ Pavement design and construction

The geotechnical engineering Scope of Services for this project included the advancement of test borings, laboratory testing, engineering analysis, and preparation of this report.

Drawings showing the site and boring locations are shown on the Site Location and

Exploration Plan, respectively. The results of the laboratory testing performed on soil samples obtained from the site during our field exploration are included on the boring logs in the Exploration Results section.

Project Description

Our initial understanding of the project was provided in our proposal and was discussed during project planning. A period of collaboration has transpired since the project was initiated, and our final understanding of the project conditions is as follows:

Item Description

Project

Description

The project consists of the construction of a single-story golf cart storage shed covering an area of about 1,200 square feet with an associated parking/driveway area.

Planned

Foundation(s)

■ Slab-on grade with design for ¾” PVR tolerance

■ Suspended floor slab with drilled pier foundations

Finished Floor

Elevation (FFE) Unknown at the time of this report

Facilities | Environmental | Geotechnical | Materials 2

Item Description

Maximum Loads

■ Columns: 5 kips up to 15 kips

■ Walls: 1 kip/ft to 2.5 kips/ft

Grading/Slopes

Planned grading is unknown but anticipated to be within 2 feet of existing site grades.

Final slopes are planned with a maximum inclination of 3H:1V

(Horizontal: Vertical) or flatter.

Below-Grade

Structures None anticipated

Free-Standing

Retaining Walls None anticipated

Pavements

We assume rigid (concrete) and flexible (asphalt) pavement sections will be considered for the drive areas.

We understand that the traffic classification will consist of:

■ Autos and pickup trucks: Up to 250 vehicles per day

■ Light delivery and trash collection vehicles: Up to 5 per week

The pavement design period is 20 years.

Terracon should be notified if any of the above information is inconsistent with the planned construction, as modifications to our recommendations may be necessary.

Site Conditions

The following description of site conditions is derived from our site visit in association with the field exploration and our review of publicly available geologic and topographic maps.

Item Description

Parcel

Information

The project is at the existing Texas A&M University – Texarkana located at 7101 University Avenue in Texarkana, Texas.

Approximate GPS: 33.48906°, -94.10225° See Site Location

Existing

Improvements Multiple existing school buildings and concrete pavement

Current Ground

Cover Manicured grass

Facilities | Environmental | Geotechnical | Materials 3

Item Description

Existing

Topography

Based on Google Earth Pro imaging, the topography appears relatively level with about 2-feet of elevation change across the planned building footprint.

Geotechnical Characterization

We have developed a general characterization of the subsurface conditions based upon our review of the subsurface exploration, laboratory data, geologic setting and our understanding of the project. This characterization, termed GeoModel, forms the basis of our geotechnical calculations and evaluation of the site. Conditions observed at each exploration point are indicated on the individual logs. The individual logs can be found in the Exploration Results and the GeoModel can be found in the Figures attachment of this report.

As part of our analyses, we identified the following model layers within the subsurface profile. For a more detailed view of the model layer depths at each boring location, refer to the GeoModel.

Model

Layer Layer Name General Description

1 Clay Fat clay with sand, Lean clay with varying amounts of sand: stiff to very stiff

2 Sand Clayey sand, Silty sand: loose to medium dense

Groundwater Conditions

The boreholes were observed while drilling and immediately after completion for the presence and level of groundwater. The water levels observed in the boreholes can be found on the boring logs in Exploration Results and are summarized below.

Boring

Number

Approximate Boring

Depth (feet) 1

Approximate Depth to

Groundwater while

Drilling (feet) 1

Approximate Depth to

Groundwater after

Drilling (feet) 1

B-1 25 24 Dry and open to 25

B-2 15 Not observed Dry and open to 15

1. Below ground surface

The absence of groundwater in one of the borings does not necessarily mean the borings terminated above groundwater, or the water levels summarized above are stable groundwater levels. A relatively long period may be necessary for a groundwater level to

Facilities | Environmental | Geotechnical | Materials 4 develop and stabilize in a borehole. Long-term observations in piezometers or observation wells sealed from the influence of surface water are often required to define groundwater levels.

Groundwater level fluctuations occur due to seasonal variations in the amount of rainfall, runoff and other factors not evident at the time the borings were performed. Therefore, groundwater levels during construction or at other times in the life of the structure may be higher or lower than the levels indicated on the boring logs. The possibility of groundwater level fluctuations should be considered when developing the design and construction plans for the project.

Seismic Site Class

The seismic design requirements for buildings and other structures are based on Seismic

Design Category. Site Classification is required to determine the Seismic Design

Category for a structure. The Site Classification is based on the upper 100 feet of the site profile defined by a weighted average value of either shear wave velocity, standard penetration resistance, or undrained shear strength in accordance with Section 20.4 of

ASCE 7 and the International Building Code (IBC). Based on the soil properties observed at the site and as described on the exploration logs and results, our professional opinion is that a Seismic Site Classification of D be considered for the project. Subsurface explorations at this site were extended to a maximum depth of 25 feet. The site properties below the boring depth to 100 feet were estimated based on our experience and knowledge of geologic conditions of the general area. Additional deeper borings or geophysical testing may be performed to confirm the conditions below the current boring depth.

Geotechnical Overview

Design finished floor elevation for the planned building and the final grading plan were not available at the time of this report. That information should be provided to Terracon that our recommendations can be reviewed and revised if necessitated by the proposed grading plan.

The subsurface materials generally consisted of lean clay and fat clay near the surface underlain with clayey sand and silty sand. Groundwater was encountered at a depth of about 24 feet during drilling Boring B-1, but the borehole was dry upon completion of drilling the boring. Groundwater levels could be much higher during construction due to seasonal fluctuations

The near surface soils could become unstable with typical earthwork and construction traffic, especially after precipitation events. Effective drainage should be established

Facilities | Environmental | Geotechnical | Materials 5 early in the construction sequence and maintained after construction to avoid potential issues. If possible, the grading should be performed during the warmer and drier times of the year. If grading is performed during the winter months, an increased risk for possible undercutting and replacement of unstable subgrade will persist. Additional site preparation recommendations, including subgrade improvement and fill placement, are provided in the Earthwork section.

Expansive soils are present on this site. This report provides recommendations to help mitigate the effects of soil shrinkage and expansion. To reduce potential swell to less than about ¾ inches, the upper 3 feet of the subgrade profile should be low plasticity clayey sands. Even if these procedures are followed, some movement and (at least minor) cracking in the structure should be anticipated. The severity of cracking and other damage such as uneven floor slabs will probably increase if modification of the site results in excessive wetting or drying of the expansive soils. Eliminating the risk of movement and distress may not be feasible, but it may be possible to further reduce the risk of movement if significantly more expensive measures are used during construction.

Some of these options are discussed in this report such as a structural slab.

As tentatively planned by the project design team, a shallow foundation system and floor slab-on-grade on a structural fill pad can be used for the proposed building if the risk of shrink/swell and settlement movement is acceptable, and provided the subgrade is prepared as discussed in this report, including stripping, overexcavation, and placement of compacted structural fill. As an alternate, the building could be supported on drilled piers and the floor slab could be structurally suspended. Recommendations are provided in the following sections for preparation of the subgrade, and construction of the structural fill building pad, foundations, and floor slabs. The Shallow Foundations section addresses support of the building bearing on native soil or structural fill. The

Deep Foundations section addresses support of the building on drilled piers. The Floor

Slabs section addresses slab-on-grade support of the building and structurally suspended slabs.

A rigid or flexible pavement system may be used for this site. The Pavements section addresses the design of pavement systems.

The recommendations contained in this report are based upon the results of field and laboratory testing (presented in the Exploration Results), engineering analyses, and our current understanding of the proposed project. The General Comments section provides an understanding of the report limitations.

Earthwork

Earthwork is anticipated to include clearing and grubbing, excavations, and engineered fill placement. The following sections provide recommendations for use in the

Facilities | Environmental | Geotechnical | Materials 6 preparation of specifications for the work. Recommendations include critical quality criteria, as necessary, to render the site in the state considered in our geotechnical engineering evaluation for foundations, floor slabs, and pavements.

Site Preparation

Prior to placing fill, all surface material, existing vegetation, topsoil, and root mats should be removed. Complete stripping of the topsoil should be performed in the proposed building and parking/driveway areas.

No evidence of fill or underground facilities (such as septic tanks, cesspools, basements, and utilities) was observed during the exploration and site reconnaissance, but such features could be encountered during construction. If unexpected fills or underground facilities are encountered, such features should be removed, and the excavation thoroughly cleaned prior to backfill placement and/or construction.

The stripped subgrade in fill areas and final grade in cut areas should be proof rolled with an adequately loaded vehicle such as a fully-loaded tandem-axle dump truck. The proof rolling should be performed under the observation of the Geotechnical Engineer or representative. Areas excessively deflecting under the proof roll should be delineated and subsequently addressed by the Geotechnical Engineer. Such areas should either be removed or modified by stabilizing with lime or lime-flyash. Excessively wet or dry material should either be removed or moisture conditioned and recompacted.

Subgrade Preparation

If the floor slab is grade-supported, we recommend the floor slab is supported on a structural fill pad at least 3 feet thick. Structural fill placed beneath the building footprint should extend horizontally a minimum distance of 5 feet beyond the outside edge of the building. All exposed areas which will receive fill should be thoroughly proofrolled. Once the subgrade passes a proofroll, then compacted structural fill soils should be placed to the proposed design grade and the moisture content and compaction of subgrade soils should be maintained until foundation construction.

Based upon the subsurface conditions determined from the geotechnical exploration, subgrade soils exposed during construction are anticipated to be relatively workable;

however, the workability of the subgrade may be affected by precipitation, repetitive construction traffic or other factors. If unworkable conditions develop, workability may be improved by scarifying and drying.

Facilities | Environmental | Geotechnical | Materials 7

Excavation

We anticipate that excavations for the proposed construction can be accomplished with conventional earthmoving equipment. The bottom of excavations should be thoroughly cleaned of loose soils and disturbed materials prior to backfill placement and/or construction.

Fill Material Types

Fill required to achieve design grade should be classified as structural fill and pavement fill. Structural fill is material used below, or within 5 feet of structures. Pavement fill is material used below pavements.

Imported Fill Materials: Imported fill materials should meet the following material property requirements. Regardless of its source, compacted fill should consist of approved materials that are free of organic matter and debris.

Soil Type 1

USCS

Classification and Parameters

Acceptable Placement Location

Structural Fill

Clayey Sand (SC)

4≤PI≤18

Less than 45% passing on No. 200 sieve

Must be used to construct the structural fill pad under the grade-supported slab.

Structural fill should also be considered below exterior flatwork to reduce potential movements.

Pavement Fill

Clayey Sand (SC) or Sandy Lean Clay

(CL)

4≤PI≤25

Recommended for pavement fill and other areas outside the building. Silty sands and sandy silts are sensitive to moisture content, and might have constructability issues during compaction.

1. Structural and pavement fill should consist of approved materials free of organic matter and debris. A sample of each material type should be submitted to the Geotechnical Engineer for evaluation prior to use on this site.

Reuse of On-Site Soil: Excavated near surface soil is not expected to be suitable for reuse as structural fill and should not be placed beneath settlement sensitive structures and within foundation bearing zones. Excavated lean clays may be selectively reused as pavement fill provided the material is evaluated prior to use.

Fill Placement and Compaction Requirements

Structural and pavement fill should meet the following compaction requirements.

Facilities | Environmental | Geotechnical | Materials 8

Item Structural Fill and Pavement Fill

Maximum Lift

Thickness

8 inches or less in loose thickness when heavy, self-propelled compaction equipment is used

4 to 6 inches in loose thickness when hand-guided equipment

(i.e. jumping jack or plate compactor) is used

Minimum

Compaction

Requirements 1,2,3

95% of maximum

98% of maximum below 5-foot depth where fill thickness is greater than 5 feet

Water Content

Range

-3% to +3% of optimum

1. Maximum density and optimum water content as determined by the standard

Proctor test (ASTM D 698).

2. High plasticity cohesive fill should not be compacted to more than 100% of standard Proctor maximum dry density.

3. If the granular material is a coarse sand or gravel, or of a uniform size, or has a low fines content, compaction comparison to relative density may be more appropriate. In this case, granular materials should be compacted to at least

70% relative density (ASTM D 4253 and D 4254). Materials not amenable to density testing should be placed and compacted to a stable condition observed by the Geotechnical Engineer or representative.

Utility Trench Backfill

Any soft or unsuitable materials encountered at the bottom of utility trench excavations should be removed and replaced with structural fill or bedding material in accordance with public works specifications for the utility be supported. This recommendation is particularly applicable to utility work requiring grade control and/or in areas where subsequent grade raising could cause settlement in the subgrade supporting the utility.

Trench backfill should be mechanically placed and compacted as discussed earlier in this report. Compaction of initial lifts should be accomplished with hand-operated tampers or other lightweight compactors. Where trenches are placed beneath slabs or footings, the backfill should satisfy the gradation and expansion index requirements of engineered fill discussed in this report. Flooding or jetting for placement and compaction of backfill is not recommended.

For low permeability subgrades, utility trenches are a common source of water infiltration and migration. Utility trenches penetrating beneath the building should be effectively sealed to restrict water intrusion and flow through the trenches, which could migrate below the building. The trench should provide an effective trench plug that extends at least 5 feet from the face of the building exterior. The plug material should

Facilities | Environmental | Geotechnical | Materials 9 consist of cementitious flowable fill or low permeability clay. The trench plug material should be placed to surround the utility line. If used, the clay trench plug material should be placed and compacted to comply with the water content and compaction recommendations for structural fill stated previously in this report.

Grading and Drainage

All grades must provide effective drainage away from the building during and after construction and should be maintained throughout the life of the structure. Water retained next to the building can result in soil movements greater than those discussed in this report. Greater movements can result in unacceptable differential floor slab and/or foundation movements, cracked slabs and walls, and roof leaks. The roof should have gutters/drains with downspouts that discharge onto splash blocks at a distance of at least 10 feet from the building.

Exposed ground should be sloped and maintained at a minimum 5% away from the building for at least 10 feet beyond the perimeter of the building. Locally, flatter grades may be necessary to transition ADA access requirements for flatwork. After building construction and landscaping have been completed, final grades should be verified to document effective drainage has been achieved. Grades around the structure should also be periodically inspected and adjusted, as necessary, as part of the structure’s maintenance program. Where paving or flatwork abuts the structure, a maintenance program should be established to effectively seal and maintain joints and prevent surface water infiltration.

Earthwork Construction Considerations

Shallow excavations for the proposed structure are anticipated to be accomplished with conventional construction equipment. Upon completion of filling and grading, care should be taken to maintain the subgrade water content prior to construction of floor slabs and pavements. Construction traffic over the completed subgrades should be avoided. The site should also be graded to prevent ponding of surface water on the prepared subgrades or in excavations. Water collecting over or adjacent to construction areas should be removed. If the subgrade freezes, desiccates, saturates, or is disturbed, the affected material should be removed, or the materials should be scarified, moisture conditioned, and recompacted prior to floor slab construction.

During seasons of significant rainfall, the groundwater table could affect overexcavation efforts, especially for overexcavation and replacement of lower strength soils. A temporary dewatering system consisting of sumps with pumps may be necessary to achieve the recommended depth of overexcavation depending on groundwater conditions at the time of construction. Groundwater should be maintained at least 2 feet below the bottom of excavations to help maintain stability during construction.

Facilities | Environmental | Geotechnical | Materials 10

As a minimum, excavations should be performed in accordance with OSHA 29 CFR, Part

1926, Subpart P, “Excavations” and its appendices, and in accordance with any applicable local and/or state regulations.

Construction site safety is the sole responsibility of the contractor who controls the means, methods, and sequencing of construction operations. Under no circumstances shall the information provided herein be interpreted to mean Terracon is assuming responsibility for construction site safety or the contractor's activities; such responsibility shall neither be implied nor inferred.

Excavations or other activities resulting in ground disturbance have the potential to affect adjoining properties and structures. Our scope of services does not include review of available final grading information or consider potential temporary grading performed by the contractor for potential effects such as ground movement beyond the project limits. A preconstruction/ precondition survey should be conducted to document nearby property/infrastructure prior to any site development activity. Excavation or ground disturbance activities adjacent or near property lines should be monitored or instrumented for potential ground movements that could negatively affect adjoining property and/or structures.

Construction Observation and Testing

The earthwork efforts should be observed by the Geotechnical Engineer (or others under their direction). Observation should include documentation of adequate removal of surficial materials (vegetation and topsoil), evaluation and remediation of existing fill materials (if encountered), as well as proofrolling and mitigation of unsuitable areas delineated by the proofroll.

Each lift of compacted fill should be tested, evaluated, and reworked, as necessary, as recommended by the Geotechnical Engineer prior to placement of additional lifts. Each lift of fill should be tested for density and water content at a frequency of at least one test for every 2,500 square feet of compacted fill in the building areas and every 5,000 square feet in pavement areas. One density and water content test should be performed for every 50 linear feet of compacted utility trench backfill.

In areas of foundation excavations, the bearing subgrade should be evaluated by the

Geotechnical Engineer. If unanticipated conditions are observed, the Geotechnical

Engineer should prescribe mitigation options.

In addition to the documentation of the essential parameters necessary for construction, the continuation of the Geotechnical Engineer into the construction phase of the project provides the continuity to maintain the Geotechnical Engineer’s evaluation of subsurface conditions, including assessing variations and associated design changes.

Facilities | Environmental | Geotechnical | Materials 11

Shallow Foundations

If the site has been prepared in accordance with the requirements noted in Earthwork, the following design parameters are applicable for shallow foundations.

Design Parameters – Compressive Loads

Item Individual Column Continuous Wall

Maximum Net Allowable Bearing

Pressure, Dead Load Plus

Sustained Live Load 1, 2

2,000 psf 1,600 psf

Maximum Net Allowable Bearing

Pressure, Total Load 1, 2

2,400 psf 2,000 psf

Required Bearing Stratum

Structural fill or Natural competent soils

Bearing stratum to be verified by Terracon

Minimum Foundation

Dimensions 30 inches 18 inches

Ultimate Passive Resistance 4 150 psf per foot of depth

Sliding Resistance 130 psf allowable

Minimum Embedment below

Finished Grade

18 inches 18 inches

Estimated Total Settlement from

Structural Loads

Less than about 1 inch

Estimated Differential

Settlement 2, 7

About 1/2 of total settlement

1. The maximum net allowable bearing pressure is the pressure in excess of the minimum surrounding overburden pressure at the footing base elevation. Values assume that exterior grades are no steeper than 20% within 10 feet of structure.

2. Values provided are for maximum loads noted in Project Description. Additional geotechnical consultation will be necessary if higher loads are anticipated.

3. Unsuitable or soft soils should be overexcavated and replaced per the recommendations presented in Earthwork.

4. Use of passive earth pressures requires the sides of the excavation for the spread footing foundation to be nearly vertical and the concrete placed neat against these vertical faces or that the footing forms be removed and compacted structural fill be placed against the vertical footing face. Assumes no hydrostatic pressure.

5. Can be used to compute sliding resistance where foundations are placed on suitable soil/materials. Frictional resistance for granular materials is dependent on the bearing

Facilities | Environmental | Geotechnical | Materials 12

Item Individual Column Continuous Wall pressure which may vary due to load combinations. For fine-grained materials, lateral resistance using cohesion should not exceed ½ the dead load.

6. Embedment necessary to minimize the effects of frost and/or seasonal water content variations. For sloping ground, maintain depth below the lowest adjacent exterior grade within 5 horizontal feet of the structure.

7. Differential settlements are noted for equivalent-loaded foundations and bearing elevation as measured over a span of 50 feet.

Design Parameters – Overturning and Uplift Loads

Shallow foundations subjected to overturning loads should be proportioned such that the resultant eccentricity is maintained in the center-third of the foundation (e.g., e < b/6, where b is the foundation width). This requirement is intended to keep the entire foundation area in compression during the extreme lateral/overturning load event.

Foundation oversizing may be required to satisfy this condition.

Uplift resistance of spread footings can be developed from the effective weight of the footing and the overlying soils with consideration to the IBC basic load combinations.

Foundation Construction Considerations

As noted in Earthwork, the footing excavations should be evaluated under the observation of the Geotechnical Engineer. The base of all foundation excavations should be free of water and loose soil, prior to placing concrete. Concrete should be placed soon after excavating to reduce bearing soil disturbance. Care should be taken to prevent wetting or drying of the bearing materials during construction. Excessively wet or dry material or any loose/disturbed material in the bottom of the footing excavations should be removed/reconditioned before foundation concrete is placed.

Item Description

Soil Moist Unit Weight 120 pcf

Soil Effective Unit Weight 1 60 pcf

Soil weight included in uplift resistance

Soil included within the prism extending up from the top perimeter of the footing at an angle of 20 degrees from vertical to ground surface

1. Effective (or buoyant) unit weight should be used for soil above the foundation level and below a water level. The high groundwater level should be used in uplift design as applicable.

Facilities | Environmental | Geotechnical | Materials 13

Sensitive soils exposed at the surface of footing excavations may require surficial compaction with hand-held dynamic compaction equipment prior to placing structural fill, steel, and/or concrete. Should surficial compaction not be adequate, construction of a working surface consisting of either crushed stone or a lean concrete mud mat may be required prior to the placement of reinforcing steel and construction of foundations.

If unsuitable bearing soils are observed at the base of the planned footing excavation, the excavation should be extended deeper to suitable soils, and the footings could bear directly on these soils at the lower level or on lean concrete backfill placed in the excavations. The lean concrete replacement zone is illustrated on the sketch below.

Overexcavation for structural fill placement below footings should be conducted as shown below. The overexcavation should be backfilled up to the footing base elevation, with structural fill, as recommended in the Earthwork section.

Facilities | Environmental | Geotechnical | Materials 14

Drilled Piers

The project team may consider supporting the building on drilled pier foundations. It appears that underreamed bells are not practical at this site due to the granular soils observed below a depth of about 6 feet at this site. Groundwater was observed at a depth of about 24 feet during drilling at this site and if encountered during excavation, it may complicate construction of piers at the site.

Drilled Pier Design Parameters

Soil design parameters are provided below in the Drilled Pier Design Summary table for the design of drilled pier foundations. The applicability of a drilled pier foundation should be evaluated after a site topographic map and design finished subgrade elevations are made available. The values presented for allowable side friction and end bearing include a factor of safety.

Drilled Pier Design Summary 1

Depth

(feet)

Stratigraphy 2 Allowable Skin

Friction

(psf) 3

Allowable

Passive

Pressure (psf)

Allowable End

Bearing

Pressure

(psf) 4 Material

0 – 4 CL/CH/SC --- --- ---

4 – 8 CL/SC/SM 100 250 ---

8 – 25 SC/SM 190 500 6,000

1. Design capacities are dependent upon the method of installation and quality control parameters. The values provided are estimates and should be verified when installation protocol have been finalized.

2. See Subsurface Profile in Geotechnical Characterization for more details on stratigraphy.

3. Applicable for compressive loading only. Reduce to 2/3 of values shown for uplift loading. The effective weight of the shaft can be added to uplift load resistance to the extent permitted by IBC.

4. Piers should extend at least one diameter into the bearing stratum for end bearing to be considered.

5. The highest anticipated groundwater level is assumed at the ground surface.

Piers should be adequately reinforced as designed by the Structural Engineer for both tension and shear to sufficient depths. Buoyant unit weights of the soil and concrete should be used in the calculations below the highest anticipated groundwater elevation.

Facilities | Environmental | Geotechnical | Materials 15

Drilled piers should have a minimum (center-to-center) spacing of three diameters.

Closer spacing may require a reduction in axial load capacity. Axial capacity reduction can be determined by comparing the allowable axial capacity determined from the sum of individual piles in a group versus the capacity calculated using the perimeter and base of the pier group acting as a unit. The lesser of the two capacities should be used in design.

A minimum pier diameter of 18 inches should be used. Drilled piers should have a minimum length of 8 feet and should extend into the bearing strata at least one pier diameter to develop the allowable end-bearing pressures listed in the above table.

Post-construction settlements of drilled piers designed and constructed as described in this report are estimated to range from about ½ to ¾ inch. Differential settlement between individual piers is expected to be ½ to ⅔ of the total settlement.

Drilled Pier Lateral Loading

The following table lists input values for use in LPILE analyses. Such analysis should be considered if lateral loads exceed 10 kips. Modern versions of LPILE provide estimated default values of kh and E50 based on strength and are recommended for the project.

Since deflection or a service limit criterion will most likely control lateral capacity design, no safety/resistance factor is included with the parameters.

Stratigraphy1 L-Pile Soil

Model

Su

(psf)2

(pcf)2 ε50

K (pci)

Depth Material Static Cyclic

0 – 4 CL/CH/SC Soft Clay 500 --- 110 Use Default Value

4 – 8 CL/SC/SM

Sand

(Reese) --- 27° 115 Use Default Value

8 – 25 SC/SM

Sand

(Reese) --- 29° 120 Use Default Value

1. See Subsurface Profile in Geotechnical Characterization for more details on

Stratigraphy.

2. Definition of Terms:

Su: Undrained shear strength

: Internal friction angle

’: Effective unit weight

3. The highest anticipated groundwater level is assumed at the ground surface.

When piers are used in groups, the lateral capacities of the piers in the second, third, and subsequent rows of the group should be reduced as compared to the capacity of a

Facilities | Environmental | Geotechnical | Materials 16 single, independent pier. Guidance for applying p-multiplier factors to the p values in the p-y curves for each row of pile foundations within a pile group are as follows:

Center to Center Pier

Spacing 1,2

P-Multiplier, Pm

Front Row Second Row

Third and

Subsequent

Rows

3B 0.8 0.4 0.3

4B 0.9 0.65 0.5

5B 1.0 0.85 0.7

6B 1.0 1.0 1.0

1. Spacing in the direction of loading. B = pier diameter

2. For the case of a single row of piers supporting a laterally loaded grade beam, group action for lateral resistance of piers would need be considered when spacing is less than three pier diameters (measured center-to-center).

3. See adjacent figure for definition of front, second and third rows.

Spacing closer than 3D (where D is the diameter of the pier) is not recommended without additional geotechnical consultation due to potential for the installation of a new shaft disturbing an adjacent installed shaft likely resulting in axial capacity reduction.

Drilled Pier Construction Considerations

The drilling contractor should be experienced in the subsurface conditions observed at the site, and the excavations should be performed with equipment capable of providing a clean bearing surface. The drilled pier foundation system should be installed in general accordance with the procedures presented in "Drilled Shafts: Construction Procedures and Design Methods," FHWA Publication No. FHWA-NHI 18-024.

The contractor is generally expected to use conventional “dry” techniques for installation of the drilled piers. Subsurface water was encountered at a depth of about 24 feet in

Boring B-1 during drilling. Subsurface water levels are influenced by seasonal and climatic conditions, which result in fluctuations in subsurface water elevations.

Additionally, it is common for water to be present after periods of significant rainfall.

Casing or slurry drilling procedures could be required in soils zones of higher sand content to reduce the potential for excavation sidewall collapse.

Facilities | Environmental | Geotechnical | Materials 17

The drilling contractor should remove all soft and disturbed soils from the base of the drilled pier prior to placing concrete. The drilled pier installation process should be performed under the observation of the Geotechnical Engineer. The Geotechnical

Engineer should document the pier installation process including soil/rock and groundwater conditions observed, consistency with expected conditions, and details of the installed pier.

To prevent collapse of the sidewalls and/or to control groundwater seepage, the use of temporary steel casing and/or slurry drilling procedures may be required for construction of the drilled pier foundations. Significant seepage could occur in case of excavations penetrating water-bearing sandy soil and/or highly broken bedrock layers. The drilled pier contractor and foundation design engineer should be informed of these risks.

The use of temporary steel casing and/or slurry drilling procedures may be required at this site during drilled pier construction to reduce the potential for collapse of the sidewalls within sand seams and layers and control groundwater seepage. If casing is removed during concrete placement, care should be exercised to maintain concrete inside the casing at a sufficient level to resist earth and hydrostatic pressures present on a casing exterior. Water or loose soil should be removed from the bottom of the drilled piers prior to placement of the concrete.

Use of a telescoping casing arrangement can be considered to avoid handling long casing lengths. The lower casing should be of sufficient length and stiffness and have an appropriate cutting edge to allow it to be firmly seated into the bedrock to seal out groundwater. If possible, excess water should be evacuated from the casing to place concrete in the “dry.”

Care should be taken to not disturb the sides and bottom of the excavation during construction. The bottom of the pier excavation should be free of loose material before concrete placement. Concrete should be placed as soon as possible after the foundation excavation is completed, to reduce potential disturbance of the bearing surface.

Floor Slabs

Based on the information developed from our field and laboratory programs and on method Tex-124-E in the Texas Department of Transportation (TxDOT) Manual of

Testing Procedures, we estimate that the subgrade soils have Potential Vertical Rise

(PVR) values ranging between about 1 inch and 1 ½ inches at the existing ground surface. Those PVR values were estimated using existing moisture conditions, as well as assuming dry conditions for the upper 6 feet, and average to wet conditions below 6 feet. The actual movements could be greater if poor drainage, ponded water, and/or other sources of moisture are allowed to infiltrate beneath the structures after

Facilities | Environmental | Geotechnical | Materials 18 construction. Removal of existing soil and/or placement of fill would change the PVR values, as would changing the moisture conditions used for analysis.

To provide an estimated PVR of about ¾ inches or less at the finished subgrade surface of the building and to provide uniform bearing for the floor slab, a building pad of structural fill soil at least 3 feet thick should be constructed below the design finished subgrade elevation. This may require overexcavation of existing soil, with the depth of overexcavation depending on the design finished floor elevation.

The thickness of structural fill required to provide a PVR of about ¾ inches maximum at the finished subgrade surface of the building should be further evaluated after the site topographic map, final grading plan, and design finished floor elevations are available.

The structural fill pad should extend a minimum of 5 feet beyond the edge of the proposed structure. The final exterior grade adjacent to the building should be sloped to promote positive drainage away from the structure. Following overexcavation of the soil to the specified depth, and prior to placement of structural fill, the exposed subgrade soils should be thoroughly proof-rolled and/or evaluated by Terracon using other methods, and prepared as outlined in Earthwork.

The subgrade and structural fill soils should be prepared as outlined in Earthwork, which contains material and placement requirements for structural fill, as well as other subgrade preparation recommendations. Design parameters for the floor slabs assume the requirements for Earthwork have been followed. Specific attention should be given to positive drainage away from the structure.

Floor Slab Design Parameters

Item Description

Slab Support Structural fill at least 3 feet thick

Estimated Potential Vertical Rise (PVR) Approximately ¾ inches

The slab should be structurally independent of spread footing or continuous footing foundations that are not cast monolithically with the slab to allow independent movement. Saw-cut control joints should be placed in the slab to help control the location and extent of cracking. For additional jointing recommendations, refer to the

ACI Design Manual.

The use of a vapor retarder or barrier should be considered beneath concrete slabs-on-grade that will be covered with wood, tile, carpet or other moisture-sensitive or impervious coverings, or when the slab will support equipment or materials sensitive to moisture. When conditions warrant the use of a vapor retarder, the slab designer and slab contractor should refer to ACI 302 and ACI 360 for procedures and cautions

Facilities | Environmental | Geotechnical | Materials 19 regarding the use and placement of a vapor retarder/barrier. Any “leveling or cushion” sand beneath the vapor retarder should be compacted.

Floor Slab Construction Considerations

Finished subgrade, within and for at least 10 feet beyond the floor slab, should be protected from traffic, rutting, or other disturbance and maintained in a relatively moist condition until floor slabs are constructed. If the subgrade should become damaged or desiccated prior to construction of floor slabs, the affected material should be removed and structural fill should be added to replace the resulting excavation. Final conditioning of the finished subgrade should be performed immediately prior to placement of the floor slab support course.

Terracon should observe the condition of the floor slab subgrade immediately prior to placement of the floor slab support course, reinforcing steel, and concrete. Attention should be paid to high traffic areas that were rutted and disturbed earlier, and to areas where backfilled trenches are located.

Structurally Suspended Floor Slabs

Consideration may be given to use of a structurally suspended bottom floor system supported on drilled piers. We recommend a void space at least 8 inches high be provided below all elements of the bottom floor system including the grade beams.

Drainage beneath the structure must be designed to remove and/or reduce the possibility of water accumulation in the void space. The subgrade below the floor slab should be sloped to appropriate drainage outlets. Surface and subsurface drainage of water away from the building will enhance the performance of the foundations.

In addition, proper ventilation should be provided to reduce the possibility that a high humidity environment could develop in the void space areas. Measures should be taken to maintain voids beneath the exterior grade beams.

Pavements

General Pavement Comments

Pavement designs are provided for the traffic conditions and pavement life conditions as noted in Project Description and in the following sections of this report. A critical aspect of pavement performance is site preparation. Pavement designs noted in this section must be applied to the site which has been prepared as recommended in the

Earthwork section.

Facilities | Environmental | Geotechnical | Materials 20

Support characteristics of subgrade for pavement design do not account for shrink/swell movements of an expansive clay subgrade, such as soils observed on this project. Thus, the pavement may be adequate from a structural standpoint, yet still experience cracking and deformation due to shrink/swell related movement of the subgrade.

Subgrade Soil Treatment

Pavement design grades are expected to require cuts and fills. Following stripping and cutting to design grade, and prior to placement of any fill, the pavement subgrade should be proof rolled to detect any soft areas. After design subgrade elevation is achieved by cutting and filling, we recommend that the top 8 inches of the finished subgrade soils directly beneath the pavement be chemically treated. Chemical treatment will increase the supporting value of the subgrade and decrease the effect of moisture on subgrade soils. We recommend that Terracon observe the subgrade soils following cut and fill to the design pavement subgrade elevation in order to determine the type of chemical(s) that would be the most appropriate for treatment of the subgrade soil. We anticipate that lime or lime-flyash would be the most appropriate chemicals for treatment of the upper pavement subgrade soils that exist at this site. Recommended specifications for treatment of the subgrade soil with lime and lime-flyash are presented subsequently in this report.

Pavement Design Parameters

Design of pavements for the project has been based on the guidelines outlined in the

1993 Guideline for Design of Pavement Structures by the American Association of State

Highway and Transportation Officials (AASHTO-1993).

The following table summarizes the minimum design ESALs used for the pavement classifications for this project.

Minimum ESAL Values

Pavement Classification Flexible Pavement ESALs Rigid Pavement ESALs

Heavy Duty 2,500,000 3,250,000

Medium Duty 150,000 250,000

Light Duty 30,000 50,000

Pavement Section Thicknesses

The following table provides our opinion of minimum thickness for AC sections:

Facilities | Environmental | Geotechnical | Materials 21

Asphaltic Concrete Design

Layer Thickness (inches)

Light Duty 1 Medium Duty 1 Heavy Duty 1

Asphaltic Concrete Surface2 2 3 2.5

Asphaltic Concrete Base2 0 0 5

Aggregate Base3 6 7 8

Chemically Treated

Subgrade Soil 8 8 8

1. See Project Description for more specifics regarding traffic assumptions.

2. All materials should meet the current TxDOT specifications.

■ Asphaltic Surface – TxDOT Item 340, Type D…