Fairbanks Landing- Geotechnical Report.pdf

Report Cover Page

Commercial Development- Fairbanks Geotechnical Engineering Report Houston, Texas

November 5, 2025 | Terracon Project No. 92255244

Prepared for:

Freehill Fairbanks, LP 1221 South Mopac Expressway, Suite 320 Austin, Texas 78746

11555 Clay Road, Suite 100 Houston, Texas 77043

P (713) 690-8989 Terracon.com

Facilities | Environmental | Geotechnical | Materials

Report Cover Letter to Sign

November 5, 2025

Freehill Fairbanks, LP 1221 South Mopac Expressway, Suite 320 Austin, Texas 78746

Attn: Mr. William Paton

Re: Geotechnical Engineering Report Commercial Development- Fairbanks 9220 Fairbanks North Road Houston, Texas Terracon Project No. 92255244

Dear Mr. Paton:

Terracon Consultants, Inc. (Terracon) is pleased to submit our geotechnical engineering report for the project referenced above in Houston, Texas. We trust that this report is responsive to your project needs.

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 Consultants, Inc.

(Texas Firm Registration No.: F-3272)

Miguel Ortiz-Cahun, Ph.D., E.I.T. Yongwan Kwon, P.E.

Senior Staff Engineer Group Manager

Geotechnical Engineering Report Commercial Development- Fairbanks | Houston, Texas November 5, 2025 | Terracon Project No. 92255244

Facilities | Environmental | Geotechnical | Materials i

Table of Contents Introduction Project Description Site Conditions Geotechnical Characterization

Geology GeoModel Groundwater Conditions

Geotechnical Overview Earthwork

Site Preparation Fill Material Types Fill Compaction Requirements Utility Trench Backfill Grading and Drainage Wet Weather/Soft Subgrade Considerations

Foundation Systems Design Recommendations – Shallow Spread/Strip Footings Construction Considerations – Shallow Spread/Strip Footings Design Recommendations – Deep Foundation Systems Construction Considerations – Drilled Straight shafts Construction Considerations – Augered Cast-in-Place (ACIP) Piles Foundation Construction Monitoring

Floor Slabs Detention Pond

Excavation and Slopes Erosion Potential Use of Excavated Soils

Pavements General Comments

Figures GeoModel

Attachments

Exploration and Testing Procedures Site Location and Exploration Plans Exploration and Laboratory Results Supporting Information

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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/

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Introduction

Terracon Consultants, Inc. (Terracon) is pleased to submit our Geotechnical Engineering report for the proposed construction of two single-story warehouse buildings planned on a site located at 9220 Fairbanks North Road in Houston, Texas. This project was authorized by Mr. William Paton, Manager of Freehill Fairbanks, LP through signature of our “Agreement for Services” on July 2, 2025, as well as a change order signed on August 4, 2025. This project was performed in general accordance with Terracon Proposal No. P92255244.Revision2 and Terracon Project No. 92255244.ChangeOrder1, dated June 30, 2025 and August 1, 2025 respectively.

The purpose of these services was to provide information and geotechnical engineering recommendations relative to:

■ Boring logs with field and laboratory data;

■ Description of subsurface conditions;

■ Groundwater levels observed during drilling;

■ Site and boring location plans;

■ Site and subgrade preparation recommendations;

■ Foundation design and construction recommendations;

■ Detention pond construction considerations; and

■ Pavement design guidelines.

The geotechnical engineering Scope of Services for this project included the advancement of 48 test borings, laboratory testing, engineering analysis, and preparation of this report.

Maps 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 and Laboratory Results section.

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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

Information Provided

An email request for proposal was provided by Freehill Fairbanks, LP on May 28, 2025. The request included a Google Earth image of the site, and conceptual plan drawings of the planned development.

Proposed

Improvements1,2

■ Two single-story warehouse building with a footprint area of approximately 125,623 and 678,875 square feet each.

■ Three detention ponds with a maximum depth of 10 feet with a wet bottom and sideslope declinations of 3H:1V (Horizontal:Vertical), located at the western and eastern portions of the site.

■ Associated surficial pavements.

Building Construction

Steel-frame construction with a grade-supported slab over ground improvement.

Finished Floor

Elevation1,2

■ Building 1: 113 El

■ Building 2: 112 El We understand that the existing grade elevation ranges from approximately 107 to 109 feet. In addition, we understand that a maximum of 4 feet of fill is planned in the building areas.

Maximum Loads ■ Column loads: 100 to 150 kips

■ Floor slab pressure: 150 pounds per square foot (psf)

Planned Foundation

System1,3

Either drilled straight shafts, augered cast-in place piles (ACIP), or shallow spread/strip footings over rammed aggregate piers.

Pavements We assume both rigid (concrete) and flexible (asphalt) pavement sections are being considered.

Anticipated Traffic Consists primarily of passenger vehicles in the parking areas and passenger vehicles combined with garbage trucks and large multi-axle delivery trucks from time-to-time in driveway areas.

1. Based on information provided by the client.

2. Based on information provided by Quiddity on October 14 and October 31.

3. Based on discussions with the client, we understand that ground improvement through the use of rammed aggregate piers is planned if shallow foundations are planned. No engineering recommendations for rammed aggregate piers will be provided in this report.

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Site Conditions

The following description of site conditions is derived from our site visit in association with the field exploration.

Item Description

Project Size and Location

The project, about 68½ acres in size, is located at 9220 Fairbanks North Road in Houston, Texas. See Site Location.

Existing

Improvements1

The site was vacant at the time of our field program. In addition, a sand pit, with an assumed maximum depth of about 50 feet, was previously located at the project site. The backfilling activities of the sand pit were unknown at the time of our field program.

Current Ground Cover

Grass, weeds, and scattered trees.

Existing Topography

Relatively level.

1. Based on information provided by the client.

Geotechnical Characterization

Geology

Based on the geologic maps published by the Bureau of Economic Geology, the site for the proposed project is located on the upper Lissie formation, sometimes denoted the Montgomery formation. The upper Lissie formation is heterogeneous, containing interbedded layers of clay, sand and silt. This formation was deposited in mid- Pleistocene time in shallow coastal river channels and flood plains.

The clay present in the formation has been preconsolidated by a process of desiccation.

Numerous wetting and drying cycles have produced a network of randomly oriented and closely-spaced joints, which are sometimes slickensided, that is, have a shiny appearance when exposed. The joint pattern strongly influences the engineering behavior of the soil.

The sand layers vary in compactness from loose to very dense, and in thickness from a fraction of an inch to many feet due to an irregular depositional environment. Sands are generally subrounded to subangular and vary from coarse to very fine, are poorly graded, and often contain significant amounts of silt-sized particles in the sand matrix.

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The coastal plain in this region has a complex tectonic geology, several major features of which are: Gulf Coastal geosyncline, salt domes, and major sea level fluctuations during the glacial stages, subsidence and geologic faulting activities. Most of these geologic faulting activities have ceased for millions of years, but some are still active. A detailed geologic fault investigation and study of the site geology are beyond the scope of this report.

GeoModel

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 and Laboratory Results and the GeoModel can be found in the Figures attachment of this report.

Fill soils were observed at the ground surface and extended to depths that ranged from about 13 to 53 feet. The underlying native subsurface soils at the boring locations drilled at this site generally consisted of lean clay, fat clay, and silty/clayey sand soils to the termination depths of the borings (about 40 to 70 feet).

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

Fill: Lean

Clay gray, reddish brown and tan, with sand and silt pockets and seams, scattered roots, scattered gravel, ferrous stains, and calcareous nodules

2 Fill: Fat Clay gray and reddish brown, with sand and silt pockets and seams, scattered gravel, ferrous stains, and calcareous nodules

Fill: Sand and Clayey Sand gray and reddish brown, with plastic fragments

4 Lean Clay reddish brown, gray and tan, medium stiff to hard, with sand and silt pockets and seams, ferrous stains, and calcareous nodules

5 Fat Clay reddish brown, tan and light gray, medium stiff to very stiff, with silt seams, ferrous stains, and calcareous nodules

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Model Layer

Layer Name General Description

Silty Sand and Clayey

Sand gray, reddish brown and tan, very loose to very dense, with clay pockets

Groundwater Conditions

Borings B-1 through B-44 were advanced using dry drilling techniques to depths that ranged from approximately 18 to 35 feet in an effort to evaluate groundwater conditions at the time of our field program. Wet rotary techniques were used thereafter to the termination depths of these borings (about 40 to 70 feet). Borings B-45 through B-48 were advanced using dry drilling techniques to its termination depth (approximately 5 feet). Upon reaching groundwater, drilling was suspended for a period of about 15 minutes to allow the groundwater to rise and the groundwater levels to be recorded. The water levels observed in the boreholes can be found on the boring logs in Exploration and Laboratory Results and are summarized below.

Summary of Groundwater Level Observations1

Boring No.

Approximate Boring Depth

(feet)2

Depth of Dry

Drilling

(feet)2

Approximate Depth of Groundwater (feet)2

Initial/ During

Dry Drilling

After 5 Minutes

After 15 Minutes

After 24 hours

B-1 50 23 23 -- 173 --

B-2 50 38 35 -- -- --

B-3 50 25 -- -- 193 --

B-4 65 35 35 -- -- --

B-5 50 25 25 -- 173 --

B-6 50 18 18 17 16 --

B-7 65 354 -- -- -- 9½

B-8 65 354 -- -- -- --

B-9 65 35 35 -- -- --

B-10 55 35 35 -- -- --

B-11 50 35 35 -- -- --

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Summary of Groundwater Level Observations1

Boring No.

Approximate Boring Depth

(feet)2

Depth of Dry

Drilling

(feet)2

Approximate Depth of Groundwater (feet)2

Initial/ During

Dry Drilling

After 5 Minutes

After 15 Minutes

After 24 hours

B-12 55 35 35 -- -- --

B-13 65 35 35 -- -- --

B-14 50 35 35 -- -- --

B-15 50 35 35 -- -- --

B-16 50 35 35 -- -- --

B-17 55 35 35 -- -- --

B-18 65 35 35 -- -- --

B-19 55 35 35 -- -- --

B-20 70 35 -- -- -- 12

B-21 50 35 35 -- -- --

B-22 65 35 35 -- -- --

B-23 50 35 35 -- -- --

B-24 65 35 35 -- -- --

B-25 60 35 35 -- -- --

B-26 65 35 -- -- -- --

B-27 50 35 23 -- -- --

B-28 65 35 35 -- -- --

B-29 50 35 -- 35 -- --

B-30 65 35 35 -- -- --

B-31 50 30 30 21 18 13½

B-32 55 35 35 -- -- --

B-33 55 35 35 -- -- --

B-34 65 35 35 -- -- --

B-35 50 35 35 -- -- --

B-36 50 35 35 -- -- --

B-37 65 35 35 -- -- --

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Summary of Groundwater Level Observations1

Boring No.

Approximate Boring Depth

(feet)2

Depth of Dry

Drilling

(feet)2

Approximate Depth of Groundwater (feet)2

Initial/ During

Dry Drilling

After 5 Minutes

After 15 Minutes

After 24 hours

B-38 50 35 35 -- -- --

B-39 55 35 35 -- -- --

B-40 55 35 -- -- -- 11

B-41 55 35 -- -- -- 10

B-42 55 35 -- -- -- 10¾

B-43 40 30 30 -- -- --

B-44 40 30 35 -- -- --

B-45 5 5 -- -- -- --

B-46 5 5 -- -- -- --

B-47 5 5 -- -- -- --

B-48 5 5 -- -- -- --

1. Groundwater readings were obtained on date.

2. Below existing grade.

3. Caved-in.

4. Groundwater readings were not obtained due to utilizing wet rotary drilling techniques.

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 structures 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 and should be evaluated prior to construction.

Geotechnical Overview

Based on the information obtained from our subsurface exploration, the site can be developed for the proposed project. A summary of our findings and recommendations is provided below.

■ Fill soils were observed at the ground surface at borings B-1 through B-48 and extended to depths that ranged from about 13 to 53 feet. Fill soils may be

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Facilities | Environmental | Geotechnical | Materials 8 present at varying depths and at other locations not explored during our field program. Support of the foundation elements, slabs, flatworks, and pavements on or above fill soils is discussed in this report. We understand that ground improvement will be utilized to support the grade supported slab and reduce the potential for settlement. We do not recommend grade-supported slabs be utilized without ground improvement due to the depth of undocumented fill soils which may result in excessive settlement of the slabs. The design and recommendations for ground improvement will be provided by others.

■ The surficial soils observed in portions of the site exhibited low plasticity and an increased silt and sand content. These soils are moisture sensitive and may become weak with elevated moisture contents and present construction difficulties. If wet and/or soft conditions are present at the time of construction, remedial efforts may be necessary for preparation of the surficial soils in the building and pavement areas to create a working surface. Remedial effort options are discussed in the Wet Weather/Soft Subgrade section of this report.

■ Expansive soils were observed at this site. This report provides recommendations to help reduce the effects of soil shrinkage and expansion. However, even if these procedures are followed, some movement and distress in the building and pavement should be anticipated. The severity of distress will increase if any modification of the site results in excessive wetting or drying of the expansive soils. Eliminating the risk of movement associated with expansive soils may not be feasible. However, this risk can be significantly reduced if the building is designed as a structural slab over a void space with the structural loads supported by a foundation system terminated below the active zone. Terracon can provide recommendations for this option, if requested.

■ A foundation system consisting of either drilled straight shafts, augered cast-in place piles (ACIP), or shallow spread/strip footings over rammed aggregate piers may be utilized to support the proposed buildings planned at this site. Shallow spread/strip footing over rammed aggregate piers recommendations will be provided by others.

■ A minimum 36-inch thick select fill building pad should be placed under the proposed buildings to provide uniform support to the floor slab and reduce the estimated Potential Vertical Rise (PVR) of the subgrade to approximately one inch or less. In addition, we understand the grade-supported slabs will be supported over ground improvement. We do not recommend grade-supported slabs be utilized without ground improvement due to the depth of undocumented fill soils which may result in excessive settlement of the slabs. The design and recommendations for ground improvement will be provided by others.

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■ Based on the soil conditions observed at borings B-39 through B-44, which were drilled in the proposed detention pond areas, these soils should support sideslopes for the anticipated maximum excavation depth of 10 feet with sideslope declinations of 3(horizontal):1(vertical) or flatter. In addition, we understand that the pond is planned to maintain a permanent water level of approximately 4¾ feet.

■ Pavement areas placed upon the deeper fill soils will also be subject to future settlement of the fill. Complete excavation, removal, and recompaction of the fill soils in the pavement areas would reduce the potential for future settlement;

however, complete excavation and removal of the fill soil within the proposed pavement areas would likely not be feasible. As an alternative, the settlement potential can be reduced by reworking the upper two to three feet of fill below the pavement areas if deep fills soils are observed (or up to the underlying native soils, whichever occurs first) to reduce differential settlements, with the understanding that some settlement (which will likely result in increased maintenance of pavements) may occur.

■ Rigid pavement sections vary from 5.0 to 7.0 inches of reinforced concrete with chemically treated subgrade.

■ Flexible pavement sections vary from 2.0 to 2.5 inches of asphaltic concrete over

8.0 to 10.0 inches of base material with chemically treated subgrade.

This summary should be used in conjunction with the entire report for design purposes.

Details were not included or fully developed in this section, and the report must be read in its entirety for a comprehensive understanding of the items contained herein. The section titled General Comments should be read for an understanding of the report limitations.

Earthwork

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

Site Preparation

Construction areas should be stripped of vegetation, topsoil, trees, and other debris/unsuitable surface material. Proper site drainage should be maintained during

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Facilities | Environmental | Geotechnical | Materials 10 construction so that ponding of surface runoff does not occur and cause construction delays and/or inhibit site access.

Pavement areas placed upon the deeper fill soils, if observed, will also be subject to future settlement of the fill. Complete excavation, removal, and recompaction of the fill soils in the pavement areas would reduce the potential for future settlement; however, complete excavation and removal of the fill soil within the proposed pavement areas would likely not be feasible. As an alternative, the settlement potential can be reduced by reworking the upper two to three feet of fill below the pavement areas if deep fills soils are observed (or up to the underlying native soils, whichever occurs first) to reduce differential settlements, with the understanding that some settlement (which will likely result in increased maintenance of pavements) may occur.

Once final subgrade elevations have been achieved, the exposed subgrade should be carefully proofrolled with a 20-ton pneumatic roller or equivalent equipment, such as a fully loaded dump truck, to detect weak zones in the subgrade. Special care should be exercised when proofrolling areas containing fill soils in an attempt to observe soft/weak zones within the fill soils. Weak areas detected during proofrolling, as well as zones of fill containing organic matter and/or debris, should be removed and replaced with soils exhibiting similar classification, moisture content, and density as the adjacent in-situ soils. Proofrolling should be performed under the direct observation of the Geotechnical Engineer or his/her representative.

Subsequent to proofrolling, and just prior to placement of fill, the exposed subgrade within the construction area should be evaluated for moisture and density. If the moisture and/or density do not meet the criteria described in Fill Compaction Requirements for on-site soils, the subgrade should be scarified to a minimum depth of 6 inches, moisture adjusted, and compacted to at least 95 percent of the Standard Effort (ASTM D698) maximum dry density.

Fill Material Types

Select fill and on-site soils to be used at this site for grade adjustments should meet the following criteria:

Fill Type

USCS

Classification Acceptable Location for Placement

Select Fill Soils CL and/or SC

(10≤PI≤20)

Must be used to construct the select fill building pad under the grade-supported slab (if any) and for all grade adjustments within the building areas.

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Fill Type

USCS

Classification Acceptable Location for Placement

On-site Soils Varies

The on-site soils, including the undocumented fill soils, appear suitable for use as fill within the pavement areas, provided they are free of organics and debris.

If blended or mixed soils are intended for use as select fill, Terracon should be contacted to provide additional recommendations. Blended or mixed soils do not occur naturally.

These soils are a blend of sand and clay and will require mechanical mixing at the site with a pulvimixer. If these soils are not mixed thoroughly to break down the clay clods and blend-in the sand to produce a uniform soil matrix, the fill material may be detrimental to the performance of the foundations. If blended soils are used, we recommend that additional samples of the blended soils as well as the clay clods, be obtained prior to and during earthwork operations to evaluate if the blended soils can be used in lieu of select fill. The actual type and amount of mechanical mixing at the site will depend on the amount of clay and sand, and properties of the clay.

Fill Compaction Requirements

Item Description

Fill Lift Thickness The fill soils should be placed on prepared surfaces in lifts not to exceed 8 inches loose measure, with compacted thickness not to exceed 6 inches.

Compaction Requirements

■ The select fill and on-site soils should be compacted to at least 95 percent of the Standard Effort (ASTM D698) maximum dry density.

■ The select fill soils should be moisture adjusted to within 2 percent of the optimum moisture content.

■ The on-site clay soils should be moisture conditioned to between optimum and +4 percent of the optimum moisture content.

Prior to any filling operations, samples of the proposed borrow and on-site materials should be obtained for laboratory moisture-density testing. The tests will provide a basis for evaluation of fill compaction by in-place density testing. A qualified soil technician should perform sufficient in-place density tests during the filling operations to evaluate that proper levels of compaction, including dry unit weight and moisture content, are being attained.

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Utility Trench Backfill

Utility trenches are a common source of water infiltration and migration. All utility trenches that penetrate beneath the buildings should be effectively sealed to restrict water intrusion and flow through the trenches that could migrate below the buildings.

We recommend constructing an effective clay “trench plug” that extends at least 5 feet out from the face of the building exterior. The plug material should consist of clay compacted at a water content at or above the soils optimum water content. The clay fill should be placed to completely surround the utility line and be compacted in accordance with recommendations in this report.

Grading and Drainage

All grades must provide effective drainage away from the buildings during and after construction. Water permitted to pond next to the buildings can result in distress in the buildings. These greater movements can result in unacceptable differential floor slab movements, cracked slabs and walls, and roof leaks. Building slab and foundation performances described in this report are based on effective drainage for the life of the structures and cannot be relied upon if effective drainage is not maintained.

Exposed ground should be sloped away from the buildings for at least 10 feet beyond the perimeter of the structures. After building construction and landscaping, we recommend verifying final grades to document that effective drainage has been achieved. Grades around the structures should also be periodically inspected and adjusted as necessary, as part of the structures’ maintenance program.

Planters located within 10 feet of the proposed buildings should be self-contained to prevent water accessing the building and pavement subgrade soils. Locate sprinkler mains and spray heads a minimum of 5 feet away from the building lines. Low-volume, drip-style landscaped irrigation should not be used near the buildings. Collect roof runoff in drains or gutters. Discharge roof drains and downspouts onto pavements and/or flatworks which slope away from the proposed buildings or extend down spouts a minimum of 10 feet away from buildings.

Flatworks and pavements will be subject to post construction movement. Maximum grades practical should be used for paving and flatwork to prevent water from ponding.

Allowances in final grades should also consider post-construction movement of flatwork, particularly if such movement would be critical. Where paving or flatwork abuts the building, effectively seal and maintain joints to prevent surface water infiltration.

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Wet Weather/Soft Subgrade Considerations

Due to the elevated silt and sand content and negligible to low plasticities of the surficial soils observed at this site, proper compaction may be difficult to achieve. In addition, construction during and soon after wet weather periods may encounter difficulties due to wet and soft surficial soils becoming a general hindrance to equipment as a result of rutting and/or pumping of the soil surface. This condition is primarily due to their lack of cohesion (low clay content) and little to no confining pressure near the ground surface.

If the subgrade cannot be adequately compacted to the minimum densities as described above, one of the following methods should be used to improve the soils: 1) removal and replacement with select fill, 2) chemical treatment of the soil to dry the subgrade, or

3) drying by natural means if the schedule allows.

Based on our experience with similar soils, chemical treatment is an efficient and effective method to improve the condition of wet and soft subgrade such as that observed at this site. Chemical treatment may be necessary to depths of approximately one to 2 feet or greater of the surficial silty/sandy soils, depending on the condition of the subgrade at the time of construction. We suggest that a cost be included in the construction budget for chemical treatment of the soils using a lime-flyash mixture to aid drying and improve the condition of the soil if the soil is wet and/or soft at the time of construction. We recommend that this cost be in the form of a contingency or allowance to be used if needed.

Foundation Systems

Based on our conversations with the client, we understand that the proposed buildings are planned to be supported using a foundation system consisting of either drilled straight shafts, augered cast-in place piles (ACIP), or shallow spread/strip footings over rammed aggregate piers (RAP). We understand that rammed aggregate piers will be designed by others.

Based on the subsurface conditions observed during our field and laboratory programs, these types of foundation systems may be utilized to support the proposed structures planned at this site, provided the subgrade is properly prepared as described in this report. Recommendations for these types of foundation systems are provided in the following sections, along with other geotechnical considerations for this project.

Design Recommendations – Shallow Spread/Strip Footings

Item Description

Minimum Embedment Depth 1 4 feet below existing grade (grade at the time of our field program)

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Item Description Allowable Bearing Pressures (Individual and Strip Footings) 2

Provided by the chosen specialty contractor Approximate Post-Construction

Settlement 3

Allowable Passive Pressure 4 750 psf

Allowable Frictional Resistance 5 250 psf

Uplift Resistance 6 Foundation Weight (150 pcf) & Soil Weight (120 pcf)

1. The footings should bear upon on-site ground improved soils.

2. We understand that ground improvement is being considered at this site. We understand that allowable bearing pressure will be evaluated by the chosen specialty contractor.

3. We recommend the RAP system be designed to limit settlement of the proposed shallow spread/strip footings to one inch or less.

4. The passive pressure along the exterior face of the footings should be neglected within the upper 4 feet due to surface effects and the presence of fill and expansive soils unless pavement is provided up to the edge of the structures. For interior footings, the allowable passive pressure may be used for the entire depth of the footing.

5. To be utilized on the base of the footings

6. Structural uplift loads on the shallow footings may be resisted by the weight of the foundation plus the weight of any soil directly above the foundation. The ultimate uplift capacity of shallow footings should be reduced by an appropriate factor of safety to compute allowable uplift capacity.

Construction Considerations – Shallow Spread/Strip Footings

Excavations for shallow footings should be performed with equipment capable of providing a relatively clean bearing area. The bottom 6 inches of the foundation excavations should be completed with a smooth-mouthed bucket or by hand labor. The excavations should be neatly excavated and properly formed. Debris in the bottom of the excavation should be removed prior to steel placement. Based on the groundwater observations obtained during our field program (refer to Groundwater Conditions), significant groundwater seepage is not anticipated for shallow footings at the recommended bearing depth. However, water should not be allowed to accumulate at the bottom of the foundation excavations. To reduce the potential for groundwater seepage into the excavations and to minimize disturbance to the bearing area, we recommend that concrete and steel be placed as soon as possible after the excavations are completed. Excavations should not be left open overnight. The bearing surface of the shallow footings should be evaluated immediately prior to placing concrete or a seal slab.

A thin seal slab of lean concrete (approximately 2 to 4 inches thick) should be placed at the bottom of the footing excavation to protect the bearing surface of the footings from

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Facilities | Environmental | Geotechnical | Materials 15 disturbance and/or infiltration of ground/surface water if the footing cannot be poured within the same day of excavation.

Design Recommendations – Deep Foundation Systems

Allowable skin friction and end bearing values for drilled straight shaft and ACIP piles are presented in the following tables. These design parameters were computed based on a generalized soil profile and engineering properties of the subsurface soils observed within the depths explored at this site.

Design Parameters for Drilled Straight Shaft Footings

Below Existing Grade (feet) 1

Allowable Unit Skin Friction Resistance

(psf)

Allowable End Bearing Pressure (psf)

0 to 6 Disregard Disregard 6 to 50 125 Disregard

50 to 70 550 6,000

1. Grade at the time of our field program.

Design Parameters for ACIP piles

Below Existing Grade (feet) 1

Allowable Unit Skin Friction Resistance

(psf)

Allowable End Bearing Pressure (psf)

0 to 6 Disregard Disregard 6 to 50 175 Disregard

50 to 70 700 6,000

1. Grade at the time of our field program.

A minimum penetration of 2 feet into the desired bearing strata with a minimum of 4 feet of the selected bearing stratum below the bottom of the shaft is required to achieve the recommended allowable end bearing values provided in the above table. The deep foundations should extend through any fill soils and be placed to bear within the native clay soils at a minimum depth of 50 feet below existing grade. Design of deep foundations should also include an evaluation of the structural capacity of the foundation element which may limit the allowable capacity.

There are numerous factors which contribute to the behavior of groups subjected to axial load. Several of these factors are foundation type, size and length, spacing, overall group size, loading conditions, installation procedures and soil type and strength. We recommend a minimum spacing of three diameters, center-to-center, for shafts or piles placed in groups beneath square or rectangular caps. However, for shafts or piles placed

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Facilities | Environmental | Geotechnical | Materials 16 in a linear pattern beneath load bearing walls, a minimum spacing of two diameters, center-to-center, would generally be acceptable. Closer spacing than three diameters in groups or two diameters in rows could result in increased group settlement and a reduction of load-carrying capacity of individual foundation elements.

Settlement of a single, isolated shaft or pile will depend on the elastic properties of the foundation, the applied load, and the interaction of the soil and foundation. Settlement is anticipated to be primarily elastic and will occur relatively soon as load is applied.

Significant consolidation settlement due to applied load is not anticipated for the allowable capacities. Our experience indicates that a single, isolated foundation loaded to about one-half of its ultimate capacity will result in settlements of about one inch or less. Groups generally undergo more settlement than single, isolated foundation elements for the same applied load. Based on the above recommended spacing, we anticipate that settlement of a group will be on the order of one inch under working loads with differential settlement between foundations to be about one-half inch.

The deep foundations will provide resistance to lateral loads through the passive earth pressure acting on the side of the foundation. A detailed lateral load analysis of the proposed deep foundations was beyond the scope of this project. If requested, a detailed lateral load analysis of the proposed deep foundations can be performed by Terracon.

Lateral loads should not exceed the structural capacity of the individual drilled straight shaft or pile.

The deep foundations will provide resistance to structural uplift loads through the mobilization of the skin friction acting at the interface of the shaft or pile sidewall and the adjacent soils. The allowable skin friction values provided in the previous tables may be used to calculate the uplift resistance for the shafts or piles.

As presented in Construction Considerations - Augered Cast-in-Place (ACIP), we recommend that at least one full scale ACIP pile load test be performed to evaluate the actual ACIP pile capacity at this specific site.

Construction Considerations – Drilled Straight shafts

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 area. The drilled straight-shaft foundation should be installed in general accordance with the procedures presented in "Drilled Shafts: Construction Procedures and LRFD Design Methods," by Brown, D.A., Turner, J.P., and Castelli, R.J., FHA Publication No. FHWA-NHI-10-016, 2010 and "Standard Specification for the Construction of Drilled Piers", ACI Publication No. 336.1-01, 2001.

The successful completion of the drilled straight shaft will depend to a large extent on the suitability of the equipment and the operator's skills. The operation sequence should

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Facilities | Environmental | Geotechnical | Materials 17 be scheduled so that the shaft excavation can be completed, reinforcing steel placed, and the concrete poured in a continuous, rapid, and orderly manner to minimize the time the excavation is open. Concrete should be placed as soon as practical and in all instances should be placed within the same day in order to use the side friction values recommended in this report.

Based on the subsurface conditions observed, the installation of drilled straight shafts may require the use of the Slurry Displacement Method and/or temporary steel casing due to the presence of sandier/siltier zones or groundwater. If drilled shaft installation is attempted without utilizing Slurry Displacement Method or temporary casing, zones of sloughing soils and/or groundwater inflow may occur during construction. Therefore, we recommend that provisions be incorporated into the plans and specifications to utilize slurry or casing to control sloughing and/or groundwater seepage during shaft construction.

The need for casing or slurry will depend on the depth of the drilled shaft and the groundwater conditions at the time of construction. If casing is used and seepage persists, the water accumulating in the foundation excavation should be pumped out.

The condition of the bearing surface should be evaluated immediately prior to placing concrete, if casing is used in lieu of slurry. If groundwater inflow is too severe to be controlled by the use of casing and pumping or significant sloughing of the sidewalls occurs, the slurry method of construction should be utilized to complete the foundation installation.

Where casing is used, removal of the casing should be performed with extreme care and under proper supervision to minimize mixing of the surrounding soil and water with the fresh concrete. Rapid withdrawal of the casing may develop a suction that could cause the soil and water to flow into the excavation. An insufficient head of concrete in the casing during withdrawal could also allow the water to intrude into the wet concrete.

Under no circumstances should loose soil be placed in the annulus between the casing and the drilled shaft sidewalls. The casing must be removed in order to utilize the skin friction values previously provided.

During slurry displacement, the foundation excavation is filled with a slurry mixture. The level of slurry should be maintained above the groundwater level to maintain a positive head in the foundation excavation. Therefore, the slurry tends to seep out of the excavation, rather than the groundwater seeping into the open excavation. The slurry must be maintained in the foundation excavation until design termination depth is achieved and should be removed only as concreting proceeds. The properties of the slurry including the density, viscosity, and pH must be carefully controlled and should be in accordance with Item 416 of Texas Department of Transportation (TXDOT) Standard Specifications for Construction of Highways, Streets, and Bridges.

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Facilities | Environmental | Geotechnical | Materials 18

Slurry left in place for long periods of time will build up on the sides of the shaft causing a reduction in skin friction.

The following procedures and equipment are recommended for installation of drilled shafts by the Slurry Displacement Method:

■ The bottom of the drilled straight shaft should be cleaned as well as practical just prior to concreting to remove cuttings.

■ The concrete should be placed by means of a tremie with a one-way valve to prevent slurry from entering the pipe. The tremie should extend to the bottom of the drilled shaft to allow displacement of the slurry during concrete placement.

■ During concrete placement, the end of the tremie should remain several feet within the concrete mass to reduce the entrapment of slurry. A tremie embedment of 5 to 10 feet is generally considered acceptable.

■ The concrete should be relatively fluid to reduce the entrapment of slurry. We recommend that concrete with a slump of 6 to 8 inches be used.

■ The upper few feet of concrete should be expunged from the shaft excavation if found to be contaminated with slurry or soil.

A surface casing may be required in addition to the slurry for shaft installation at this site if sloughing of near surface soils occurs. Where casing is used, removal of the casing should be performed with extreme care as previously discussed in this section.

Production shaft installation should be observed by a qualified technician experienced in drilled shaft installation techniques. At a minimum, the technician should observe shaft excavation, note any unusual installation occurrences, observe slurry properties and/or casing installation and removal, observe concrete placement and generally evaluate if shaft installation is being performed in accordance with project specifications.

Construction Considerations – Augered Cast-in-Place (ACIP) Piles

The performance of ACIP piles is dependent on installation procedures. We recommend the following measures be taken for ACIP pile installation at this site:

■ The grout pump should be calibrated. The Deep Foundation Institute (DFI) Inspector’s Guide provides guidelines for grout pump calibration that should be followed. We recommend the grout pump be calibrated at the beginning of the project and recalibrated after any significant pump maintenance or repairs.

Calibration of the pump is critical to monitoring the incremental grout factor during installation and determining the overall grout factor for each pile.

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Facilities | Environmental | Geotechnical | Materials 19

■ The grout used should be measured frequently to maintain consistency. In accordance with the Proceedings of the 83rd Annual Transportation Research Board (TRB) meeting, grout flow rates between 10 to 25 seconds utilizing a typical ¾-inch diameter flow cone are considered appropriate.

■ An initial grout head should be developed at the bottom of excavation, prior to withdrawal of the auger. A positive pressure head of at least 5-foot of grout should be maintained at all times. We recommend that the initial 5-foot of grout be pumped prior to initial withdrawal of the auger, rather than over-pumping the initial 5-foot increment.

■ The number of pump strokes required to maintain the 5-foot of head should be determined during installation of the test reaction piles and can be visually monitored by observing the “grout return depth” upon removal of the auger. A grout return depth of 5 to 10 feet is generally considered acceptable.

■ Grouting of the piles should continue until grout contaminated with soil cuttings has stopped flowing from the hole and uncontaminated grout has completely filled the hole.

■ Field observations should be made to confirm the amount of grout used in each pile. According to data published by the DFI, the grout factor, or total volume of the grout in each pile, should be at least 115 percent of the theoretical volume for each pile. In order to promote a uniform pile diameter, we recommend that the incremental grout factor (volume) be measured for each 5-foot increment of pile length.

■ The grout pressure should be monitored during the field grouting and maintained at a pressure between 350 to 500 psi to reduce the potential for grout necking and soil caving.

Production ACIP pile installation should be closely observed by a qualified technician experienced in ACIP pile installation. The installation sequence and technique should be evaluated to determine that ACIP pile installation is being performed in general accordance with project specifications.

Varying installation methods and soil conditions can have an effect on the soil-pile interaction and capacity. We recommend that at least one full scale pile load test be performed to evaluate the actual ACIP pile capacities of each type of pile planned to be used at this specific site. The results of load test on production type piles can be analyzed to estimate unit skin friction (even though the piles are not instrumented) and, depending on the results, potentially justify the use of higher capacities than computed.

The pile for the load test should extend to a depth similar to the proposed design depth of the piles at the site. Terracon should be involved in evaluating and selecting the appropriate depths for the test piles. The test piles should be tested to failure as defined

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Facilities | Environmental | Geotechnical | Materials 20 by pile test load procedures. Installation of test piles should be identical to planned production installation procedures.

Foundation Construction Monitoring

The performance of the foundation systems for the proposed structures will be highly dependent upon the quality of construction. Thus, we recommend that fill pad compaction and foundation installation be observed full time by an experienced Terracon soil technician under the direction of our geotechnical engineer. During foundation installation, the base of the foundation excavations should be observed to evaluate the condition of the subgrade. We would be pleased to develop a plan for compaction and foundation installation observation to be incorporated in the overall quality control program.

Floor Slabs

The following recommendations are to reduce the potential of vertical rise (PVR) under the floor slabs for the proposed buildings. We understand the at-grade slabs will be sitting on a ground improvement system. We do not recommend a grade-supported slab without the use of ground improvement due to the depth of fill soils and the potential for excessive settlement.

As previously discussed, finished floor elevation for building 1 and building 2 are planned to be 113 and 112 feet, respectively, which is approximately 4 feet above existing grade. If the grading is planned to be altered from what has been previously described, Terracon should be notified to review and/or modify our recommendations given in this subsection.

The near surface soils observed at this site generally exhibit a variable expansion potential. These soils can subject the interior floor slab of the building to significant movements (due to shrinking and swelling) with fluctuations in their moisture content.

This movement potential is influenced primarily by the properties of the subgrade soils, as well as the moisture content of the subgrade at the time of construction, overburden pressures, and the stability of the moisture contents throughout the life of the building.

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 at this site exhibit a Potential Vertical Rise (PVR) of up to approximately 2¼ inches. Therefore, we highly recommend that the near-surface soils be prepared as stated below to reduce the potential for slab movement associated with volumetric changes of the near-surface clay soils due to moisture variations to a more acceptable level. The actual movements could be greater

November 5, 2025 | Terracon Project No. 92255244

Facilities | Environmental | Geotechnical | Materials 21 if poor drainage, ponded water, and/or other…