Geotechnical_Report-.pdf

GEOSCIENCE ENGINEERING & TESTING, INC.

GEOTECHNICAL EXPLORATION

City of Conroe - Well No. 5 Proposed Water Well Re-Drilling 1199 N First Street Conroe, Texas PO Number: 26-02414

Reported to:

City of Conroe Engineering Conroe, Texas

Prepared by:

Geoscience Engineering and Testing, Inc.

Houston, Texas

PROJECT NO: 26G13439

April 2026

April 28, 2026

700 Metcalf Street Conroe, TX 77301

Attention: Jennifer Gilmore Engineering Projects Coordinator

Reference: GEOTECHNICAL EXPLORATION City of Conroe - Well No. 5 Proposed Water Well Re-Drilling 1199 N First Street Conroe, Texas PO Number: 26-02414

GETI NO: 26G13439

Dear Jennifer Gilmore:

GEOSCIENCE ENGINEERING & TESTING, INC. (GETI) is pleased to submit this report for the above-referenced project. This study was authorized by Mr. Tara B. Gaha, PE, of the City of Conroe Engineering, through a professional agreement on March 02, 2026, and thereafter Purchase Order No. 26-02414, dated March 04, 2026, based on GETI Proposal No. 26-13150, dated February 22, 2026. This report briefly describes the procedures employed in our investigation and presents the conclusions and recommendations of our studies.

We appreciate the opportunity to work with you on this phase of the project. If you have any questions concerning this report or require additional information, please contact us.

With Kindest Regards, Geoscience Engineering & Testing, Inc.

Jozyril Jalique, EIT Roham Golrokh, PE Telfryn L. John, PE Staff Engineer Vice President - Engineering Services Principal Engineer

F-4802 Copies Submitted: (1)

GETI NO.: 26G13439

Table of Contents

I. INTRODUCTION

II. SUBSURFACE EXPLORATION

1. General

2. Description of the Site

3. Field Investigation

3.1. Field Strength Tests

3.2. Water Level Measurement

4. Surface Fault

5. Laboratory Testing

III. GENERAL DESCRIPTION OF SUBSURFACE MATERIALS

1. Swell Potential

2. Potential Vertical Rise (PVR)

IV. FOUNDATION RECOMMENDATION

1. Foundations and Risks

2. Foundation Discussion

2.1 Shallow Foundation (Slab-on-Grade) Design Parameters for MCC Bldg. and Generator Pad 7

2.2 Spread Footings for Proposed Hydro Pneumatic Tank and MCC Building

2.3 Underreamed Footings (Drilled Piers) – for the Proposed Hydro Pneumatic Tank

3. Spectral Response Accelerations

V. PAVEMENT RECOMMENDATIONS FOR SITE PARKING AREA AND ENTRY

1. Parking Lots for Light and Medium Vehicles

2. Concrete Pavement for Heavy Truck Traffic, Fire Lane, and Service Vehicles

VI. GENERAL CONSTRUCTION CONSIDERATIONS

1. Site Preparation

2. Structural Fill and Subgrade Preparation

3. Surface Drainage

4. Vegetation Control

VII. FLOODING CONSIDERATIONS - FOUNDATION SYSTEMS AND SITE DEVELOPMENT

VIII. DISCLAIMER

I. INTRODUCTION

Geoscience Engineering and Testing, Inc. (GETI) is pleased to submit this report of our geotechnical investigation of subsurface conditions at the site of the proposed City of Conroe Well No. 5, Water Well Re-Drilling project, located at 1199 N First Street in Conroe, Texas. GETI’s investigation was authorized by Mr. Tara B. Gaha, PE, of the City of Conroe Engineering, initially on March 02, 2026, and thereafter through Purchase Order No. 26-02414, dated March 04, 2026. The work was performed in accordance with GETI Proposal No. 26-13150, dated February 22, 2026.

According to the obtained drawing, the proposed project comprises 1.24 acres of land, and the proposed project includes multi-structure pads (MCC Building, Hydro Pneumatics Tank Pad, and 650kW Generator Pad), with associated pavement improvements. The purpose of the geotechnical investigation was to determine subsurface soil conditions at the site of the water well re-drilling, with particular reference to the recommendations for the design of the foundation for the buildings, pads, and recommendations associated with pavement.

II. SUBSURFACE EXPLORATION

1. General

This report presents the results of our soil exploration and foundation analysis for the proposed City of Conroe Well No. 5, Water Well Re-Drilling project, which includes multi-structure pads (MCC Building, Hydro Pneumatics Tank Pad, and 650kW Generator Pad), with associated pavement improvements. The facility for Water Well No. 5 is located at 1199 N First Street in Conroe, Texas.

The scope of this investigation included a reconnaissance of the immediate site, the subsurface exploration, field and laboratory testing, engineering analysis, and evaluation of the subsurface materials. The purpose of this subsurface exploration and analysis was to determine soil profile components and the engineering characteristics of the subsurface materials and to provide criteria for use by design engineers and architects in preparing the foundation for the proposed structures and pavement design.

The exploration and analysis of the subsurface conditions reported herein are considered in detail enough and within the scope to form a reasonable basis for the recommendations. The recommendations submitted are based on the available soil information and the preliminary design details furnished by Jennifer Gilmore with City of Conroe Engineering.

Any revision of plans for the proposed development from those enumerated in this report should be brought to the attention of the soil engineer so that he may determine if changes to the recommendations are required. If deviations from the noted subsurface conditions are encountered during construction, they should also be brought to the attention of the soil engineer.

2. Description of the Site

The site of the proposed project, upon which this subsurface exploration was undertaken, is located at 1199 N First Street in Conroe, Texas. The site was developed with existing structures, tanks, pumps and driveways; the remaining area of the site was relatively level and covered with grass. The surface soils were fat clay with sand/sandy fat clay, or clayey sand materials at the time of the drilling operation.

There were also 8 to 12 inches of base materials on the existing grade surface at B-1 and B-2 locations.

Please refer to the boring logs for more details.

The site geology for the geographic area corresponds to the “Willis Formation (coastward belt), Quaternary Period, and Pleistocene Epoch or Series1.

3. Field Investigation

The field investigation, which was completed on April 15, 2026, and performed to determine the engineering characteristics of the subsurface materials, included a reconnaissance of the project site, drilling the exploratory borings, and recovering the representative soil samples. Due to the presence of existing structures, soil test borings were drilled in area accessible to the drill rig. The City of Conroe Public Works and Engineering recommended boring locations, which were slightly moved at two locations due to existing water and electrical lines.

The subsurface soil conditions were explored by advancing and sampling 4 soil test borings. The Soil Borings B-1 through B-4 were drilled to a depth of 6-feet to 15-feet below the existing ground surface.

The following table provides more details:

BORING ID. BORING DEPTH, FT. BORING LOCATION

B-1 15 Generator Pad

B-2 15 MCC Building

B-3 15 Hydro Pneumatic Tank Pad

B-4 6 Parking Area and Entry Pavement

The approximate soil boring locations are shown on the attached Soil Borings Plan, Plate No. 1.

Sample depth and description of soil classification (based on the Unified Soil Classification System) are presented on the Soil Boring Logs, Plate Nos. 2 through 5. Keys to terms and symbols used on the soil boring logs are shown on Plate No. 6. Photographs appear on Plate Nos. 9 and 10.

The soil borings were of 3-inch nominal diameter. Both relatively undisturbed and disturbed soil samples were obtained at 2-feet intervals continuously to a depth of 12-feet, between 13 and 15-feet. The soil borings were performed with a drilling rig equipped with a rotary head conventional solid-stem augers were used to advance the holes.

1 Note: USGS, TNRIS, UTBEG, GEOLOGIC ATLAS OF TEXAS

Representative disturbed or undisturbed soil samples were obtained employing thin-walled sampling procedures in general accordance with ASTM D1587. Soil samples were identified according to the boring number and depth, and wrapped in aluminum foil and polyethylene plastic wrapping bags to prevent moisture loss and disturbance. All of the samples were transported to our geotechnical laboratory for examination, testing, and analysis. All borings were backfilled after final water readings were obtained with the soil cuttings accumulated during the drilling operation, unless noted otherwise on the soil boring logs.

3.1. Field Strength Tests

During the boring field operations, samples of the cohesive soil from the thin-walled tube were frequently tested in compression by use of a calibrated soil penetrometer to provide a measure of shear strength, to aid in characterizing the soil consistency.

3.2. Water Level Measurement

The information in this report summarizes conditions as found on the date the borings were drilled.

Ground water was NOT encountered during the drilling operation to the maximum depth of 15 feet.

Long-term monitoring of the ground water level was beyond the scope of this study. It should be noted that the ground water table may be expected to fluctuate with environmental variations such as the frequency and magnitude of rainfall and the time of the year when construction begins.

4. Surface Fault

A cursory review of available surface faulting maps2 shows that no well-documented principal fault was located within the 1-mile radius of the site. A detailed surface fault investigation is beyond the scope of this investigation. It should be noted that the coastal plains in this region have a complex geology, which includes active surface faulting.

5. Laboratory Testing

In addition to the field investigation, a supplemental laboratory investigation was conducted to ascertain additional pertinent engineering characteristics of the subsurface materials necessary in analyzing their behavior under the proposed loading conditions. During the laboratory investigation, all field soil samples from the borings were examined and classified by a soil engineer. Laboratory tests were then performed on selected soil samples to evaluate and determine the physical and engineering properties of the soils in accordance with the prescribed ASTM standards and methods.

2 Note: USGS, Verbeek and Clanton (1978), Shah and Lanning-Rush (2005)

Laboratory tests performed are subsequently identified, along with UU Triaxial test results. Other index properties are recorded on the boring logs.

LABORATORY TEST TEST STANDARD

Moisture Content of Soils ASTM D2216

Moisture Content and In Situ Dry Density of Soils ASTM D2937

Percent Soil Particles Passing No. 200 Sieve ASTM D1140

Unconfined Compressive Strength of Cohesive Soils ASTM D2166

Liquid Limit, Plastic Limit, and Plasticity Index of Soils ASTM D4318

Unconsolidated-Undrained Triaxial Compression Test on Cohesive Soils ASTM D2850

The strength properties of the soils were determined by means of a hand penetrometer in the field and Unconfined Compression (UC), and Unconsolidated Undrained Triaxial Compression tests performed in the laboratory on undisturbed samples.

Tests noted were performed to establish the index properties and to aid in the proper classification of the subsurface soils. Index test results are shown on the soil boring logs , Plates Nos. 2 through 5.

DESCRIPTIONS No. of Test DESCRIPTIONS No. of Test

Hand Penetrometer Test 23 Unconfined Compressive Test 3

Moisture Content Test 24

Percent soil passing No. 200 Sieve 4

Atterberg Limits 10 UU Triaxial Compression Test 2

Dry Density Test 3

LEFT BLANK INTENTIONALLY

III. GENERAL DESCRIPTION OF SUBSURFACE MATERIALS

The specific subsurface stratigraphy, as determined by field exploration, is shown in detail on the soil boring logs herein. However, the stratigraphy can be generalized as follows:

STRATUM

NUMBER

RANGE OF

DEPTH, Ft.

BORING

NO.

SOIL DESCRIPTION

I

0 – 15’ B-1 Soft to very stiff, reddish-tan, light gray, reddish-brown, and tan FAT CLAY WITH SAND/ SANDY FAT CLAY (CH)*

2 – 15’ B-2 & B-3

0 – 6’ B-4

II 0’ – 2’ B-2 & B-3 Very stiff, brown and reddish-tan CLAYEY SAND (SC)*

* Soil Classification is in accordance with the Unified Soil Classification System (USCS) and TEX 141-E.

Laboratory test results for the soils indicate Liquid Limits (LL) ranging from 25 to 84 percent, Plasticity Indices (PI) ranging from 11 to 53, and moisture contents from 11 to 32 percent.

1. Swell Potential

Based on plasticity index results, the encountered sandy fat clay, fat clay with sand, and clayey sand subsoils are characterized as having medium to very high shrink/swell potential.

When the moisture content of clay soil increases, the volume increases; conversely, when the moisture content of this type of soil decreases, the soil volume decreases. The volume changes can result in foundation movement and stress.

2. Potential Vertical Rise (PVR)

The magnitude of the moisture-induced vertical movement was calculated using the Texas Department of Transportation method (Tex-124-E) in conjunction with the current moisture profile. Based on the method, the potential vertical rise (PVR) at the locations of the proposed MCC Building, Generator Pad, and Hydro Pneumatic test borings (B-1, B-2, and B-3) drilled is estimated to be about 4 to 4¼ - inches.

More movement may occur in areas where the soil dries, and water subsequently ponds during or after construction. Site grading may also influence the potential for movement.

The estimated PVR value is reduced to approximately 1-inch when 4½-feet of the existing topsoil is replaced with structural select fill material with a Liquid Limit (LL) less than 35 percent and a Plasticity Index (PI) between 10 to 20. Alternatively, the estimated PVR value can be reduced to less than 1-inch by stabilizing the top 8-inches of the cut grade with 6% lime and elevating the grade with at least 3½-feet of compacted sandy clay structural select fill material with a Liquid Limit (LL) that does not exceed 35 and a Plasticity Index (PI) between 10 to 20.

Please note the recommended fill thicknesses in the foundation recommendations sections, as well.

IV. FOUNDATION RECOMMENDATION

FOR MCC BUILDING, GENERATOR PAD, AND HYDRO PNEUMATIC TANK PAD

(Based on Borings B-1, B-2 and B-3)

1. Foundations and Risks

Many lightly loaded foundations are designed and constructed based on economics, risks, soil type, foundation shape, and structural loading. Many times, due to economic considerations, higher risks are accepted in foundation design. It should be noted that some levels of risk are associated with all types of foundations. All these foundations must be stiffened in the areas where expansive soils are present, and trees should be removed prior to construction.

A general discussion of flooding considerations related to foundation systems and site development is subsequently provided in this report.

2. Foundation Discussion

In general, the foundation for the structures must satisfy two independent criteria. First, the maximum design pressure exerted at foundation levels should not exceed the allowable net bearing pressure based on an adequate factor of safety concerning soil shear strength. Second, the magnitude of total and differential settlements or heave under sustained foundation loads must be such that the structure movement is within tolerable limits.

Various types of foundations, such as Slab-on-Grade, Spread Footing, Underreamed Drilled (Belled) footing, Straight Shaft Footing, etc., have been discussed for the support of the proposed structure.

Based on the field investigation and laboratory test results, the soils are fat clay with sand, sandy fat clay, and clayey sand subsoils having medium to very high shrink/swell potential. Details of soil strata are given in soil boring logs, Plate Nos. 2 through 5.

In our opinion, for this type of soil strata Shallow Foundation Designs: Slab-on-Grade, and Spread Footing are considered suitable foundation systems. Details are given in the following sections.

2.1 Shallow Foundation (Slab-on-Grade) Design Parameters for MCC Bldg. and Generator Pad

The structure at this site can be supported on a foundation system comprised of Slab-On-Grade. This option will require the removal of roots, organic and unsuitable materials, and replacement with structural select fill as outlined in the “Structural Fill and Subgrade Preparation”.

Due to the soil characteristics at this site, at least 42-inches of structural select fill materials having a Liquid Limit less than 35 and a Plasticity Index (PI) between 10 & 20 are required to minimize the possibility of vertical displacement. Structural select fill material can be used to elevate the grade, or the existing grade can be undercut for placing structural select fill material. If positive site drainage is not provided nor assured, the required amount of structural select fill material shall be based on the PVR.

Based on the soil condition revealed by the field soil test boring and laboratory tests, it is our understanding that the structure at the site can be supported on a foundation system comprising a thickened reinforced slab stiffened with grade beams, which can be used for this project. The grade beam under the slab should be at least 3.5-feet below the final soil grade. The recommendation design parameters are summarized below:

Bearing Capacity: Dead Load Only: 1,500 psf Total (DL + LL): 2,250 psf

Foundation slab designed in accordance with above capacity values will have a factor of safety of FS~3.0 and 2.0 with respect to shearing failure for dead and total loading, respectively. Footing weight below final grade can be neglected in the determination of design loading.

A bedding layer of leveling sand, a maximum of 2-inches thick may be placed immediately beneath the floor slab vapor barrier. A vapor barrier consisting of 6 mil plastic sheeting should be placed over the sand cushion to prevent water migration through the concrete slab. The excavation for the grade beams should be clean and free of any loose materials prior to concrete placement.

To assure firm surface soils, and to qualify the use of tabulated capacities, this site requires proof-rolling the building site with a 15-ton roller, or other equivalent suitable equipment as approved by the engineer. The proof-rolling serves to compact surficial soils and detect any soft or loose zones. The proof-rolling operations should be observed by an experienced technician.

In regions where soft soils are located from the proof roll, undercut at least 2 to 4-feet of existing soil, process, replace, and compact to provide at least 2-feet of stiff soil on the underside of grade beams; or place and compact structural select fill to provide at least 2-feet of stiff soil on the underside of grade beams. Replaced soil or the placed Structural Select fill material should be placed in a maximum 8-inch loose lift and compacted to a minimum of 95 percent of the maximum dry density as per ASTM D-698.

The moisture content should be -1% to +3% optimum moisture.

Information was not available on whether fill will actually be used to raise the site above the existing grade prior to construction. In the event fill is placed on the site, specifications should require a uniform thickness throughout the slab area and placement in accordance with our recommendation given in the section “Structural Fill and Subsurface Preparation”. Lack of proper consideration of these factors will result in additional stress and inferior slab performance.

In general, site preparation should consist of removing any grass, weeds, and undesirable materials. The exposed subgrade should be proof-rolled to detect local weak areas which should be excavated, processed, and re-compacted in loose lifts of approximately 8-inches thickness. In the floor slab, subgrade soils should be compacted to a minimum of 95% of the standard proctor Density Test (ASTM D698) at moisture content within -1% to + 3 % of optimum moisture. Tree stumps, if present, should be removed below floor slab grade and backfilled with structural select fill materials.

2.1.1 BRAB Slab Design Parameters

The BRAB study of slabs-on-ground was published in September 1962. In 1968, a revised version of the 1962 report was published which incorporated further information developed through field studies, particularly in shrink/swell soil areas. BRAB 1968 is reported to assume a rectangular mound shape (i.e.

the slab stiffness doesn’t influence the unsupported distance) and introduces an empirical support index related to climatic rating and soil properties3.

2.1.2 Wire Reinforcement Institute (WRI) Slab Design Parameters

WRI uses the same approach as the BRAB method and can be considered a modified version of BRAB.

The WRI design procedures are published as “Design of Slab-on-Ground Foundations” (1981) and “Design of Slab-on-Ground Foundations, An Update” (1996), by the Wire Reinforcement Institute (WRI).

Based on the soil conditions revealed by the field soil test borings and referring to the WRI guide from the soil parameters for Slab Design are estimated as follows.

1. Climatic Rating (Cw)

The proposed project is in Montgomery, Texas. The climatic rating index (CW) of the project site is interpolated from the Climatic Rating Chart for the continental United States map (BRAB, 1968) to be approximately 25.

2. Weighted Plasticity Index

The weighted or equivalent plasticity index of the underlying 15 feet is obtained using weighting factors 3, 2, and 1 for the first, second, and third 5-feet layers, respectively. Based on the soil conditions revealed by the field soil test borings in conjunction with 42-inches of structural select fill, the weighted or effective PI is designated to be PI~33. The weighted or equivalent PI of each boring is then modified by the Slope Correction Coefficient (CS) and the Consolidation Correction Coefficient (CO) to obtain the Effective Plasticity Index.

3. Slope Correction Coefficient (CS)

The WRI guide suggests considering the slope of the lot by using a slope correction coefficient (CS), to estimate the Effective Plasticity Index. The Site photographs show that the surface of the site is nearly flat. Based on this information and Figure 8 of WRI “Design of Slab-on-Ground Foundations” (1996), the slope correction coefficient is estimated to be 1.0.

3 Abdelmalak R.I., Soil-Structure Interaction for Shrink-Swell Soils “A New Design Procedure for Foundation Slabs on Shrink-

Swell Soils.” Ph.D. Dissertation, Texas A&M University, December 2007.

4. Consolidation Correction Coefficient (CO)

The Consolidation Correction Coefficient (CO) can be estimated from the unconfined compressive strength of the soil using Figure 9 of “Design of Slab-on-Ground Foundations” (1996). The soil samples were delivered to the GETI laboratory as in-situ strength parameters. Thus, the estimated characteristic CO factor is 0.90.

2.1.3 Summary of Design Parameters, Shallow Foundation (Slab-on-Grade) Design Parameters for Proposed MCC Building and Generator Pad

The following table summarizes the design parameters for the proposed Slab-on-Grade Foundation.

Minimum select fill thickness, ft. 3.5-feet

Estimated PVR, inch. 4 to 4½ -inch

Amended PVR, inch 1½ -inch

Climatic rating, F 25

Design Effective PI, % 33

Min. grade beam embedment depth, ft. 3.5-feet

Allowable bearing capacity (Dead Load Only), psf. 1,500

Allowable bearing capacity (Dead and Live Load) , psf. 2,250

2.2 Spread Footings for Proposed Hydro Pneumatic Tank and MCC Building

Spread Footing systems may also be considered based on the soil condition revealed by the field soil test borings, and the structure at this site can be supported on a foundation system comprising shallow spread footings. The footings should be found at a depth of at least 4-feet below the existing grade and supported on the fat clay with sand. The spread foundation design parameters are summarized below for a footing with a width that equals or exceeds 3-feet.

Due to the soil characteristics at this site, at least 42-inches of structural select fill materials having a Liquid Limit less than 35 and a Plasticity Index (PI) between 10 & 20 are required to minimize the possibility of vertical displacement. Structural select fill material can be used to elevate the grade, or the existing grade can be undercut for placing structural select fill material. If positive site drainage is not provided nor assured, the required amount of structural select fill material shall be based on the PVR.

The spread foundation design parameters are summarized below:

Allowable Bearing Capacity for square footings:

Dead Load Only: 2,000 psf.

Total (dead and live): 2,500 psf.

Spread footings designed in accordance with the above capacity values will have a factor of safety FS~3 and FS~2 with respect to shearing failure for dead and total loading respectively. Footing weight below the final grade can be neglected in the determination of design loading.

In regions where soft soils are located from the proof roll, undercut at least 4-feet of existing soil, process, replace, and compact to provide at least 2-feet of stiff soil on the underside of grade beams; or place and compact structural select fill to provide at least 2-feet of stiff soil on the underside of grade beams. The replaced soil or the placed Structural Select fill material should be placed in a maximum 8-inch loose lift and compacted to a minimum of 95 percent of the maximum dry density as per ASTM D-

698. The moisture content should be -1% to +3% optimum moisture.

The foundation for footing should be preferably skillfully excavated by utilizing equipment with a smooth-mouth bucket, or by hand. If a toothed bucket is used, excavation with this bucket should be stopped 12 inches above the final excavation grade and the excavation completed with a smooth-mouthed bucket or by hand labor. Steel should then be placed, and the footing cast (poured) on the same day as excavation. The sides of the excavation should be removed prior to steel placement. If for some reason the footing cannot be cast on the same day of excavation, a sealed slab should be placed on the exposed foundation soils.

If the foundation is formed, the edges should be backfilled with lean concrete or compacted cement-stabilized sand (two sacks of cement per cubic yard of sand). The excavation should be sloped sufficiently to create internal sumps for runoff collection and removal. All forming materials should be removed before backfilling.

No footing should be cast (poured) without the prior approval of engineers, architects, or owner’s representatives. A detailed settlement analysis was not authorized, nor performed, at this time, since the exact size and location of the footing are not known at this time. It is anticipated that the footing designed using the allowable bearing capacity will experience small settlements, which will be well within the tolerable limits for the proposed structure. A detailed settlement analysis can be performed.

The foundation should be protected against erosion because soil should be eroded; a foundation failure could occur. The footing should be designed to provide proper support for the proposed structure, associated with differential movements, which may occur due to changes in the support soil moisture contents.

2.2.1 Summary of Design Parameters - Spread Footings for the Proposed Hydro Pneumatic Tank and MCC Building

The following table summarizes the design parameters for the MCC Building Spread Footing Foundations.

Min. embedment depth, ft. 4.0-feet

Min. structural select fill thickness, ft 3.5-feet

Allowable bearing capacity (Dead Load Only), psf. 2,000 psf

Allowable bearing capacity (Dead and Live Load), psf. 2,500 psf

Approx. total settlement, inch Approx. 1-inch (for allowable load)

Approx. differential settlement, inch Approx. ¾ -inch (for allowable load)

Allowable passive pressure, psf. ½ (Kp*x 120 X H)

Allowable sliding resistance, psf. (0.30 x (weight of mat + soil over it) /1.5

Uplift resistance, psf. Weight of Footing + Soil over it

2.3 Underreamed Footings (Drilled Piers) – for the Proposed Hydro Pneumatic Tank

Based on the soil condition revealed by the field soil test borings and laboratory tests, it is our understanding that the fuel tank structure at the site can be supported on a foundation system comprised of drilled underreamed footing bearing at a depth of 14-feet below the existing grade. The pier footings should bear on the same elevation belled in the layer of very stiff, light gray and reddish tan fat clay with sand. Any difference of encountered materials during pier installation with what was discovered in this study, drilled borings, should be reported to GETI, and subsequent recommendations will be provided accordingly. Having a qualified technician to supervise pier installation is highly recommended.

The footing on these sites may be sized for an estimated net allowable bearing pressure of 4,000 psf for dead load plus sustained live load. The bearing pressure contains a factor of safety of FS~2.5 and may be increased by 25 percent for total load conditions, whichever is critical. Spacing between the centers of the two adjacent footings should be at least 3 times the bell diameter.

The plinths of the underreamed footings should be reinforced with enough reinforcing (tension) steel to resist the potential tension force caused by uplift loads due to expansive soils between the depth of seasonal moisture changes (9 to 10-feet) and the final ground surface elevation. An adhesion value of

0.5 tsf should be applied to the straight shaft portion of the drilled footings for the computation of uplift loads.

As mentioned earlier, ground water was NOT encountered in the boring to the maximum drilled depth of 15-feet. However, the water table may be expected to fluctuate with environmental variations.

Therefore, provisions should be made to readily pump out the water that may be encountered during the drilling of the piers. Wet soils along with the presence of sands may result in the caving of soils around the footings during construction. The concrete should be placed promptly in a timely manner after drilling to minimize the potential for caving of the foundation soils. In case the bell on the drilled footings cannot be constructed due to the occurrence of caving, it is recommended that the construction contractor should use cased piers or convert this Underreamed footings to Straight shaft footings immediately. Should the straight shaft footings be used due to caving of sands and high-water level, the straight shaft piers should be placed at a depth not less than 14-feet below the existing ground surface. In such cases, the net allowable bearing capacity of 4,000 psf and allowable skin friction of 200 psf can be utilized, provided that casing is not left in the shaft and slurry cake is not on the shaft sidewall. The top 5-feet of the shaft should be ignored when applying skin friction. The bottom of the piers should be dry and clean.

If water is encountered during installation, it should be pumped out prior to concrete placement. A tremie should be used to displace water with concrete. Temporary casings or drilling slurry may be adopted to stabilize the excavation and counteract encountered groundwater. In such cases, shaft piers are installed by placing concrete using the ‘slurry displacement’ or “underwater concrete placement” method using a tremie. No pier excavation should be done at a distance less than 3 pier diameters in proximity to newly cast piers for a period of at least 24 hours. We recommend that the drilling be performed under the supervision of a qualified representative of the Geotechnical Engineer.

Experience indicates that underreams can be successfully installed, and based on local practice for performing underreamed drill piers, it is recommended to utilize a 3.0:1.0 (H: V) for underream to shaft ratio. Should caving occur during belling operation, the shaft diameter may have to be increased, thereby changing the bell-to-shaft ratio. If the soil conditions warrant the changing of the shaft diameter, the structural engineer of record should be informed about any changes, because they may require a change in reinforcing steel or bell diameter. Another alternative would be to change the typical 45-degree angle of the underreamed to 60 degrees. The concrete should be placed promptly after drilling to minimize the potential for caving of the foundation soils. By the end of the day, each drilled hole must be filled with concrete, i.e., no open holes at the end of the day.

No footing should be poured without the prior approval of the project engineer, architect, or owner’s representative. Since the exact locations of the footings are not known at this time, a detailed settlement analysis was not authorized, nor performed. It is anticipated that the footing designed using the recommended allowable bearing capacity will experience a small settlement that will be within the tolerable limits for the proposed structure.

Note: The soil stratigraphy and groundwater conditions may vary within the proposed construction site.

Hence, we recommend drilling at least 2-test piers before the construction of the foundation to verify the groundwater level and soil stratigraphy at the site.

Inspection During Construction of Drilled Piers

The recommendations are based on subsoil data in the d exploration and laboratory testing. Due to the geological deposition of the Pleistocene soils in the Gulf Coastal area, variances may occur between boring locations, therefore, the footing excavations should be inspected under the supervision of a qualified representative of the geotechnical engineer to confirm that the bearing soils are similar to those encountered in our field exploration and that the footing area has been properly prepared. The geotechnical engineer should be immediately notified if any subsoil condition is uncovered that will alter the conclusions and recommendations contained in this report. Further investigation and supplemental recommendations may be required if such a condition is encountered. Prior to the placement of concrete, the footings should be inspected to monitor that:

1. The footing bears in the proper bearing strata at the depth recommended in this report.

2. The footing shafts are of the proper dimensions and reinforcing steel is placed as shown on the structural drawings.

3. The footings are concentric with the shaft and the shaft has been drilled plumb within specified tolerances.

4. Excessive cutting buildup of cutting, and any other soft compressible materials have been removed from the bottom of the excavations.

Pier Floor Slab Options There may be two options for the floor slab:

a) Slab supported by piers only: In this option slab is supported by only grade beams, which are supported by piers. In this case loads are applied on only piers. The slab should be raised from the ground surface by at least 8-inches to avoid the vertical displacement of the slab. The slab should be tied and stiffened with grade beams. Details for void boxes are given below:

Void Boxes

A void/crawl space of 8-inches may be provided beneath the grade beams. This void space allows for movement of the expansive soils below the grade beams without distressing the structural system.

Structural cardboard void forms are often used to provide this void space, and are typically placed under the grade beams to provide this void space and act as a barrier separating the grade beams from the expansive soils.

These voids may act as a channel for water to travel under a foundation system with poor area drainage, however, if this condition occurs, it may result in the subsequent swelling of the soils and an increase in subsoil moisture loads on the floor slabs.

It is our opinion that the determination of whether to provide voids under the grade beams be made by the owner, builder, engineer, or architect after both the positive and negative aspects are evaluated.

Our experience with these voids, as well as the experiences of other experts, suggests that even though they may be effective in reducing swell pressures on the grade beams, they may provide free water which would be available for absorption by slab support soils.

b) Slab supported by grade beams and sub-grade: Another option is that the slab may be supported by the grade beams and the sub-grade (soil beneath the slab). This option will require the removal of roots, organic and unsuitable materials, and replacement with structural select fill as outlined in the “Structural Fill and Subgrade Preparation”.

Due to the soil characteristics at this site, at least 42-inches of structural select fill materials having a Liquid Limit less than 35 and a Plasticity Index (PI) between 10 & 20 are required to minimize the possibility of vertical displacement. The structural select fill material can be used to elevate the grade, or the existing grade can be undercut for placing structural select fill material. If positive site drainage is not provided or assured, the required amount of structural select fill material shall be based on the PVR.

2.3.1. Summary of Design Parameters, Piers for Proposed Hydro Pneumatic Tank

The following table summarizes design parameters for the tank foundation Underreamed Piers:

Min. embedment depth, ft. 14.0-feet

Allowable bearing pressure, psf. 4,000 psf

Allowable skin friction, psf 200 (for a possible straight shaft option)

Approx. post-construction settlement Less than 1-inch

Estimated differential settlement Less than ½ -inch

Allowable passive pressure, psf ½ (Kp*x 120 X H)

*KP = see table in Section 1.2.1.

3. Spectral Response Accelerations

A response spectrum can be used to directly assess the nature of the earthquake ground motion on the structure. It is a plot of maximum displacement, velocity, or acceleration versus the natural period of a single-degree-of-freedom system.

The soil class corresponds to Site Class B/C (Medium Hard and Soft Rock) with shear wave velocity 760 m/s, and Seismic Zone 0 (Unified Building Code 1997).

According to the Uniform Building Code (1997), a response spectrum would not usually be needed for sites that have a Seismic Zone 0. Nevertheless, the U.S. Seismic Design Maps application from the USGS yielded the following spectral response accelerations for Site Class B/C (Medium Hard and Soft Rock) and 2,475 -year return period (BSE-2N), based on ASCE41-17 and seismic design maps 4

Ss (Spectral Response for 0.2s Period) = 0.071 g S1 (Spectral Response for 1s Period) = 0.042 g

4 https:\\seismicmaps.org

V. PAVEMENT RECOMMENDATIONS FOR SITE PARKING AREA AND ENTRY

(Based on Boring B-4)

Based on our field investigation and test results in the boring at the proposed pavement (B-4), the surficial soils are predominantly sandy fat clay materials. Therefore, these surface soils can be easily handled, retain compaction, and minimize or eliminate rutting if stabilized.

1. Parking Lots for Light and Medium Vehicles

Depending upon the characteristic traffic for the pavement system, GETI recommends the upper 6-inches of the exposed sandy fat clay final subgrade be stabilized by the addition of 6% lime. Lime stabilization would require the addition of 27 pounds of lime per square yard based on a subgrade thickness of 6 inches and a soil dry weight of 100 pounds per cubic foot (pcf). If the upper 8 inches of the exposed final subgrade stabilized, it would require the addition of 36 pounds of lime per square yard.

Please consider the site preparation recommendations, which are provided in the following sections.

The required quantity of lime and/or fly ash for use in stabilization, as provided above is an estimated value only. The actual stabilization requirements may vary in the field depending on conditions at the time of construction and should be established by running tests on the exposed subgrade soils at the time of construction.

The stabilized subgrade should be compacted to at least 95% of the standard proctor maximum dry density (ASTM D698) within three percentage points of the optimum moisture content. Texas Department of of Transportation 2014 Standard Specification Items 260 and 264, should be used as a procedural guide for lime treatment of the subgrade soils.

The assumptions utilized in our pavement thickness analysis are summarized on Plate No. 7. The following pavement thicknesses are based on these assumptions and procedures published by the Portland Cement Association and the National Crushed Stone Association.

Recommendations for material properties for the paving layers are provided on Plate No. 8. It is estimated that the service life for a properly constructed and maintained pavement will be in the order of 20 years. Proper civil design features, such as joint design and quantity shoulder support, should be incorporated into the plans and specifications. Joints for concrete pavements may be designed using the Texas Department of Highways Item 360.4 (Latest Revision). Periodic maintenance will be required.

Reinforcement for rigid pavement should consist of Grade 60 No. 3 bar placed at 15-inches on center in each direction. Control joints should be placed 15-ft. on center, and expansion joints should not exceed 60 ft. on center.

Automobile Only

(DI-1)

Daily EAL 5 or less

Flexible Base Rigid Pavement

2.0" Hot Mix Asphaltic Concrete 5.0" Reinforced Concrete

6.0" Crushed Limestone 6.0" Stabilized Compacted Subgrade

6.0" Stabilized Compacted Subgrade

Light Duty

Access Lanes

(DI-2)

Daily EAL 6 to 20

Flexible Base Rigid Pavement

2.0" Hot Mix Asphaltic Concrete 6.0" Reinforced Concrete

8.0" Crushed Limestone 6.0" Stabilized Compacted Subgrade

6.0" Stabilized Compacted Subgrade

Medium Duty Access Drives

(DI-3)

Daily EAL 21 to

Flexible Base Rigid Pavement

3.0" Hot Mix Asphaltic Concrete 6.0" Reinforced Concrete

8.0" Crushed Limestone 8.0" Stabilized Compacted Subgrade

8.0" Stabilized Compacted Subgrade

2. Concrete Pavement for Heavy Truck Traffic, Fire Lane, and Service Vehicles

GETI recommends that the upper 8-inches of the exposed soil final subgrade in the areas of potential heavy truck traffic be stabilized at the following rate of treatment based on a soil dry weight of 100 pcf.

Subgrade Encountered Soil Item Percent Range Per Square Yard

Fat Clay or Lean Clay Lime 6 % 35-40 lbs.

Silty Sand or Clayey Sand Lime 3 % 20-25 lbs.

Fly Ash 7 % 47-50 lbs.

The stabilized subgrade should be compacted to a minimum 95% of the Standard Proctor maximum dry density (ASTM D 698). Texas Department of Transportation 2014 Standard Specification Item 260 and 264, should be used as a procedural guide for lime treatment of the subgrade soils. and Item 265 should be used as a procedural guide for lime and fly ash stabilization of the subgrade soils

The lime is applied and initially mixed. After mellowing a minimum of 48-hours the treated soil should be pulverized where 100, 85 and 60 percent pass the 1¾ -inch, ¾-inch, and No. 4 sieve, respectively.

After satisfactory remixing, the fly ash is added and mixed.

Reinforcement for rigid pavement with a concrete thickness of 7.0 inches should consist of Grade 60 No.

4 bar placed at 24-inches in the center in each direction; and with a concrete thickness of 8.0 or 9.0-inches, No. 4 bar placed at 18-inches in the center in each direction. Control joints should not exceed 15-feet in the center, and expansion joints should not exceed 60-feet in the center. (Grade 60 for all reinforcing steel).

Based on a Portland Cement Association (PCA) procedure reported by Yoder and Witczak, “Principles of Pavement Design”, 2nd Edition, for a modulus of subgrade reaction defined as 100 lbs./in3 that can be provided with an 8-inch stabilized subgrade.

• A 7-inch concrete pavement with a modulus of rupture of 600 psi (corresponding compressive strength exceeds 4500 psi) should provide for a pavement life defined as 2,500 tandem axle load repetitions of 40 kips or less in conjunction with 37,500 single axle load repetitions of 20 kips or less, for a period of 20 years.

• An 8-inch concrete pavement with a modulus of rupture of 600 psi (corresponding compressive strength exceeds 4500 psi) should provide for a pavement life defined as 75,000 tandem axle load repetitions of 40 kips or less in conjunction with 400,000 single axle load repetitions of 20 kips or less, for a period of 20 years.

• A 9-inch concrete pavement with a modulus of rupture of 600 psi (corresponding compressive strength exceeds 4500 psi) should provide for a pavement life defined as more than 400,000 tandem axle load repetitions of 40 kips or less in conjunction within an excess of 400,000 single axle load repetitions of 20 kips or less, for a period of 20 years.

VI. GENERAL CONSTRUCTION CONSIDERATIONS

1. Site Preparation

1.1 In general, remove all vegetation, tree roots, organic topsoil, and any undesirable materials from the construction area. Tree trunks and roots under the floor slabs should be removed to a root size of less than ½ -inch. All the excavated/extracted tree holes must be backfilled with structural fill, grout or flowable fill. We recommend that the stripping depth be evaluated at the time of construction by a soil technician.

1.2 Any on-site fill soils encountered in the structure areas during construction must have records of successful compaction tests signed by a registered professional engineer that confirms the use of the fill and record of construction and earthwork testing. These tests must have been performed on all the lifts for the entire thickness of the fill. If no compaction test results are available, the fill soil must be removed, processed, and re-compacted by our recommendations of “Structural Fill and Subgrade Preparation”.

1.3 Excavation and placing select fill soils, if needed, should extend at least 2-feet beyond the edge of the structure. Should the structure pad be elevated with a higher amount of fill, the select fill soils should extend beyond the edge of the structure to equal the height of the elevated pad. A maximum distance of 5-feet select fill beyond the edge of the grade beams will suffice for the pad over 5-feet or higher thickness. The fill soils should be tested comprehensively to evaluate the degree of compaction.

1.4 Structural select Fill, used to elevate the existing grade, should have the minimum side slope in general as follows:

1.5 The subgrade areas should then be proof-rolled with a 15-ton roller, or other equivalent suitable equipment as approved by the engineer. The proof-rolling serves to compact surficial soils and detect any soft or loose zones. Any soil deflecting excessively under moving loads should be undercut to firm soils and re-compacted. The proof-rolling operations should be observed by an experienced geotechnician.

1.6 In the areas where expansive soils are present, rough grade the site with structural fill soils to ensure positive drainage. Due to their high permeability of sand, sands should not be used for site grading where expansive soils are present.

Average Slope Height (ft) Recommended Slope (H: V)

0 -2 1:1

2 – 4 2:1

4 – 6 3:1

6+ 4:1

1.7 We recommend that the site and soil conditions used in the structural design of the foundation be verified by the engineer’s site visit after all the earthwork and site preparation have been completed before the concrete placement.

2. Structural Fill and Subgrade Preparation

It is recommended that the subgrade and fill be prepared as follows:

2.7 The site should be stripped to a suitable depth to remove any topsoil and miscellaneous fill material. The exposed subgrade surface then should be proof rolled. All soft or loose soils should be removed and replaced with select fill materials.

2.2 The natural subgrade should be scarified to a minimum depth of 6-inches. The scarified soil should then be recompacted to a minimum of 95 percent of the maximum dry density as determined by the Standard Proctor Density Test (ASTM D698). The moisture content should range from -1% to +3% of optimum moisture.

2.3 The Structural Select fill should consist of clean Sandy Clay with a Liquid Limit less than 35 percent and a Plasticity Index (PI) between 10 and 20. Specifications should require a uniform thickness throughout the slab area.

2.4 The Structural Select fill material should be placed in a maximum of 8-inches loose lift and compacted to a minimum of 95 percent of the maximum dry density as per ASTM D698. The moisture content should be within -1% to +3% of optimum moisture.

2.5 A bedding layer of leveling sand may be placed beneath the floor slab vapor barrier. The leveling sand depth should not exceed 2-inches; the leveling sand must be covered with plastic sheeting.

A vapor barrier consisting of 6-mil plastic sheeting should be placed over the sand cushion to prevent water migration through the concrete slab. The excavations for the grade beams should be clear and free of any loose materials before concrete placement.

2.6 In cut areas, the soil should be excavated to grade, and the surface soils proof rolled and scarified to a minimum depth of 6-inches and recompacted to the previously mentioned density tests at the time of construction.

2.7 The select fill soil extending from the building towards the building line should be capped with on-site high plastic clay soils to retard any water seepage into subgrade soils.

3. Surface Drainage

It is recommended that the site drainage be well developed. Surface water should be directed away from the foundation soils (use a minimum of 2% with 10-feet away from the foundation). No ponding of surface water should be allowed near the structure. The following drainage precautions should always be observed during construction and after the structure has been completed.

3.1 The backfill around the structure should be a cohesive soil material, which should be moistened and compacted to at least 90-percent of standard proctor density. Any cohesionless soil material accumulated around the perimeter of the structure during construction should be removed and not allowed to be mixed with or covered by the backfill material.

3.2 Where…